Grade Level: 10 (9-11) Group Size: 3
Time Required: 45 minutes. Expendable Cost Per Group: US$ 5

Summary: In this activity, students examine how different balls react when colliding with different surfaces. Also, they will have plenty of opportunity to learn how to calculate momentum and understand the principle of conservation of momentum.
Engineering Connection: Sports engineering is becoming a popular specialty field of study. While some engineers dedicate their research to understanding collisions between balls and bats, others study the effects of a golf ball colliding with the head of a golf club. And, mechanical engineers consider momentum and collisions when designing vehicles. Learning how the human body and equipment interacts with the ball during impact or how the human body interacts with the inside of a car during a crash, helps engineers design better sports equipment and safer vehicles.

Related curriculum subject areas: Algebra, Physical Science.

Learning Objectives

After this activity, students should be able to:

* Understand that momentum depends on both mass and velocity.
* Explain the difference between an elastic and inelastic collision.
* Recognize that different surfaces and materials promote different types of collisions.
* Collect data to solve equations.
* Apply this information to topics and activities they are familiar with and can relate to from their everyday lives.

Materials List

Each group needs:

* 3 different balls (suggestions: ping-pong ball, tennis ball, racquetball, golf ball, baseball, super ball, clay, billiards ball)
* 3 different bouncing surfaces (suggestions: tile floor, linoleum floor, carpeted floor, wooden block, cinder block)
* Kilogram or gram scale
* Meter stick
* 3 copies of the Bouncing Balls Worksheet (one per student)

Introduction/Motivation

Momentum can be thought of as mass in motion and is given by the expression:

Momentum = mass x velocity

The amount of momentum an object has depends both on its mass and how fast it is going. For example, a heavier object going the same speed as a lighter object would have greater momentum. Sometimes when moving objects collide into each other, momentum can be transferred from one object to another. There are two types of collisions that relate to momentum: elastic and inelastic.

An elastic collision follows the Law of Conservation of Momentum, which states “the total amount of momentum before a collision is equal to the total amount of momentum after a collision.” An elastic collision example might involve a super-bouncy ball; if you were to drop it, it would bounce all the way back up to the original height from which it was dropped. Another elastic collision example may be observed in a game of pool. Watch a moving cue ball hit a resting pool ball. At impact, the cue ball stops, but transfers all of its momentum to the other ball, resulting in the hit ball rolling with the initial speed of the cue ball.

In an inelastic collision, momentum is not conserved and the energy is transferred to another kind of energy such as heat or internal energy. A dropped ball of clay demonstrates an extremely inelastic collision. It does not bounce at all and loses its momentum.

Instead, all the energy goes into deforming the ball into a flat blob.

In the real world, there are no purely elastic or inelastic collisions. Rubber balls, pool balls (hitting each other), and ping-pong balls may be assumed extremely elastic, but there is still some bit of inelasticity in their collisions. If there were not, rubber balls would bounce forever. The degree to which something is elastic or inelastic is dependent on the material of the object (see Figure 1).

Figure 1. The illustration of the percentage of energy returned to a ball after one bounce (or, the “range of bounciness” of each ball).

The graph above illustrates the percentage of energy returned to a ball after one bounce. The x axis displays the percentage and ball type, and the y axis displays the varying degrees of height. From left to right, and in ascending order, the following balls and percentages are shown: table tennis ball (15%), baseball (32%), golf ball (36%), soccer ball (40%), tennis ball (49%), basket ball (56%), super ball (81%) and steel ball on steel plate (98%).

In order to complete this activity, you will also need to have an understanding of the motion of an object. Following are the Kinematics equations:

d = (Vf + Vi) * t

Vf = Vi + at

d = Vi * t + ½ * a * t2

Vf2 = Vi2 + 2 * a * d

Where d is the displacement of an object, Vi is the initial velocity of the object, Vf is the final velocity, a is the acceleration of the object, and t is the interval of time the object traveled. For example, if a ball is rolled off of a table 1 meter above the ground, we can find the velocity with which it hits the floor and the time it takes to do so:

d = 1 m Vi = 0 m/s a = 9.81 m/s2 Vf = ? t = ?

d = Vi * t + ½ * a * t2

¬1 m = 0 m/s * t + ½ * 9.81 m/s2 * t2

t = 0.45 s

Vf2 = Vi2 + 2 * a * d

Vf2 = 0 m/s + 2 * 9.81 m/s2 * 1 m

Vf = 4.43 m/s

If we have three known values, then we must choose equations that use the three values that actually we do have to find the ones that we do not. You also have to read between the lines sometimes to get three known values. For example, in the problem stated previously, the value of acceleration is not given but the object is in free fall, meaning its acceleration is that of gravity.

Procedure

Before the Activity

* Gather materials.
* Make enough copies of the Bouncing Balls Worksheet so that each student has one.

With the Students

1. Determine the mass in kilograms of each ball and record it on the data sheet.
2. Drop each ball from a distance of 1 meter onto the surface and record how high it bounces in meters (example: 0.46 meters).
3. Note whether the ball and surface showed more of an elastic or inelastic collision.

* If the ball bounces up more than .5 meters, then it is more elastic.
* If it bounces up less than .5 meters, then it is more inelastic.

4. Repeat steps 1, 2 and 3 for the two other surfaces.
5. Calculate the velocity for each ball right before it bounces (question 2) and right after it bounces (question 3).
6. Calculate the momentum for each ball right before it bounces (question 4) and right after (question 5).
7. Calculate the percentage of momentum lost for each case (question 6).
8. Answer the Further Learning questions on the worksheet based on your answers. (Note: Have students complete question 11 as a group.)
9. Once the class is finished with the Bouncing Balls Worksheet, discuss which balls had the best elastic collisions on each surface. Also, if time permits go over some of the Further Learning questions as a class.

Links to worksheets

Click on Teachengineering.org website and do a curriculum search for

TE Activity: Bouncing Balls (for High School)

Safety Issues

Be sure the students do not use the balls as projectiles.

Troubleshooting Tips

This activity is best done in groups, because while one person drops the ball, another person must watch the ball and meter stick to note how high the ball bounces. Additional team members could hold the meter stick steady and/or record the data. It is difficult to get an accurate measurement for how high the ball bounces since it is in constant motion. Therefore, have students drop each ball on each surface several times, or until they have a consistent measurement.

Some balls are greatly affected by wind resistance, such as wiffle balls. Therefore, try to pick balls that will not have much influence from wind resistance since this experiment is done under the assumption there exists no wind resistance.

If students have never seen the kinematics equations, this can be a good introduction. Help the students figure out the exact equations they will need to use and walk them through the parts of the worksheets that involve the kinematics equations.

Assessment

Pre-Activity Assessment

Brainstorming: In small groups, have the students engage in open discussion. Remind students that no idea or suggestion is “silly.”

All ideas should be respectfully heard. Ask the students:

* What are sports examples of transfer and conservation of momentum? (Possible answers: Hitting a baseball with a bat, hitting the cue ball with a pool stick, the cue ball bouncing off another ball, striking a golf ball with a club or driver, or hitting a tennis ball with a racquet.)

Activity Embedded Assessment

Voting: Ask the students to vote to rank the sports (named above) from those having the greatest momentum to those having the least momentum. While the students will have to use their own judgment, remind them that momentum depends equally on mass and velocity.

Post-Activity Assessment

Problem Solving: Present the class with the following cases:

* Case 1: A big-time slugger hits a baseball 60 meters/sec (134 mph).
* Case 2: Johnny knocks down four pins at the Bowl-a-Rena by rolling a 15-pound bowling ball 1.34 meters/sec (3 mph).

Ask students which ball would bounce higher if each were thrown onto a trampoline with the given velocities. What about on concrete? (Answer: The bowling ball would bounce higher on the trampoline, while the baseball would bounce higher off of concrete.)

Discuss as a class why this is the case. Notice that the trampoline responds with a higher bounce to objects of greater mass, while the concrete causes objects with greater elasticity to bounce higher.

Activity Extensions

Students could investigate the materials used to make balls as a way to better understand why they bounce the way they do. For example, if you cut open a golf ball, you will find a mass of rubber bands wound around a core that is also usually rubber. All that rubber (and the hard plastic cover) explains its bounciness. A baseball has a similar construction, but with very different materials. A baseball’s inside is a mass of yarn wound around a cork core, and its cover material is leather. These materials make for a less bouncy ball. (Note: safety precautions should be taken when opening these balls and should be done under adult supervision.)

Activity Scaling

* If there is not enough time to complete the worksheet, have students finish it for homework.
* If students are new to the material and still unfamiliar with the equations they need for this activity, provide them the necessary equations.

References

The Physics Classroom and Mathsoft Engineering & Education, Inc., 2004, accessed May 30, 2007.

http://www.physicsclassroom.com/Class/momentum/momtoc.html

Momentum and energy loss of balls colliding against different surfaces, accessed May 30, 2007.

http://www.iit.edu/~smile/ph8709.html

The Exploratorium, Science of Baseball, accessed May 30, 2007. http://www.exploratorium.edu/baseball/index.html

The Exploratorium, Science of Baseball, accessed May 30, 2007. http://www.exploratorium.edu/baseball/howfar7.html

The Exploratorium, Science of Baseball, accessed May 30, 2007. http://www.exploratorium.edu/baseball/howfar5.html

Owner: Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder

Contributors: Bailey Jones, Matt Lundberg, Chris Yakacki, Malinda Schaefer Zarske, Denise Carlson, Ben Sprague, Janet Yowell

Copyright: © 2007 by Regents of the University of Colorado.

Grade Level: 6 (5-7) Group Size: 1
Time Required: 50 minutes

Summary: Students write a biographical sketch of an artist or athlete who lives on the edge, riding the gravity wave, to better understand how these artists and athletes work with gravity and manage risk. Note: The literacy activities for the Mechanics unit are based on physical themes that have broad application to our experience in the world — concepts of rhythm, balance, spin, gravity, levity, inertia, momentum, friction, stress and tension.
Engineering Connection: Some engineers design sports equipment for athletes who are trying to defy gravity. When athletes propel themselves by their own power, they want low-weight but durable equipment. A world-class sprinter runs in specially-designed, super light sprinting spikes. Pro cyclists want the lightest, but still strong and rigid, bicycles as they climb and descend mountains. Engineer-designed sports equipment might include boards, sails, skis, shoes, bats, masks, ropes and safety straps, helmets, clothing or bicycles.

Related Curriculum: Physical Science

Prerequisite Knowledge: familiarity with the concept of gravity

Learning Objectives

After this activity, students should be able to:

Write reports with greater detail and supporting material.
Choose vocabulary and figures of speech that communicate clearly.
Draft, revise, edit and proofread for a legible final copy.
Apply skills in analysis, synthesis, evaluation and explanation to their writing and speaking.
Incorporate source materials into their speaking and writing (for example, interviews, news articles, encyclopedia information).
Write and speak in the content areas using the technical vocabulary of the subject accurately.
Make predictions, draw conclusions and analyze what they read, hear and view.

Materials List

Paper and pencil or pen
Access to the Internet
Introduction/Motivation

What does it take to become a world-class athlete? Talent, obviously, but sometimes overlooked is the degree of drive and discipline required, which can make the difference between being a top achiever or an also-ran. This is true whether you are Michael Jordan or a star performer in Cirque du Soleil or the “extreme” athletes who compete in the Gravity Games (see http://www.gravitygames.com).

Speaking of gravity, what all these athletes have in common is the way they work with and sometimes against gravity, performing their unique forms of aerial ballet: Michael Jordan making an artful, air-bound slam dunk; gold-medalist free-style skier Eric Bergoust accomplishing the “helicopter” or “backscratcher” maneuver in the 2002 Winter Olympics; Isabelle Vaudelle and other artists performing the “Aerial Contortion in Silk” in Cirque du Soleil’s “Quidam”; Tony Hawk finally executing the 900 on the twelfth attempt at the 1999 X Games.

Think of an athlete or movement artist who has a special gift for working with gravity. This may be a famous person or someone you know who possesses the talent, drive and discipline to become world-class. Athletes are performers as much as movement artists are athletes. Your assignment is to write a brief biographical sketch of this athlete, this “performer.”

Vocabulary/Definitions

Kinesthesia: The sense that detects bodily position, weight or movement of the muscles, tendons and joints.
Orient: To align or position with respect to a point or system of reference; to become adjusted or aligned.
Vestibular system: System in the body that is responsible for maintaining balance, posture and the body’s orientation in space. This system also regulates locomotion and other movements and keeps objects in visual focus as the body moves.

Procedure

As we’ve learned, gravity isn’t just a good idea, it’s the law (a law of nature). So why has defying this law become such a popular sport? It used to be that if you wanted to see someone risk life and limb you had to wait until the circus came to town — the high-wire walker, trapeze artist, man-shot-out-of-a-cannon. Increasingly popular “new circus” troupes such as Cirque du Soleil leave out the animals and focus entirely on the arts of movement, playing with gravity in startling ways. And now, the circus has moved outdoors, as so-called extreme sports have multiplied — skateboarding, snowboarding, free-style motocross, free-style rock-climbing, free-style skiing, inline skating, extreme surfing, bungee-jumping, sky-surfing, wakeboarding. The list continues to grow. Daredevils now live next door.

Building upon the gravity concepts learned in this lesson (Mechanics unit, Lesson 2), in this activity, students write a biographical sketch of a person who defies gravity for fun, for art, for glory, for profit or for a combination of these motives. The object of writing the sketch is not just to answer the “who” and what but also the “how” and “why” of the gravity defiers.

Students approaching adolescence may already consider risk-taking forms of behavior to be glamorous. Extreme sports are certainly presented as such. This literacy activity can also be an opportunity to look behind the glamour. For a skeptical view of extreme sports — and some discussion points — see Dudes vs. Nature by Joyce Millman (http://www.salon.com/weekly/extreme960603.html). An excerpt:

The extreme sportsters’ attempts to change the proportions of a world in which people are increasingly powerless and small is not without poignance, though. This is the generation that grew up on Spielberg, video games and cyberspace — in their imaginations and egos, if not in actuality, anything is possible.

For all the hype, extreme sports are real sports, challenging mind and body in new and exciting ways. Extreme athletes are also like circus performers or performance artists who make a profession and an art of tuning their bodies to a fine edge of achievement. In writing the biographical sketch, students should be encouraged to consider just how such artists and athletes work both with and against gravity to perfect their edge-walking art.

As students are encouraged to develop critical thinking skills, they may begin to question why certain cultural forms and activities emerge and not take them at face value, looking beneath the glamour of the sport to the reality of the physical discipline that is required to become a world-class athlete, new circus performer or aerial dancer.

Note: In the literacy activity, Wow! That Captures It, for Mechanics unit, Lesson 6, students use the concept of “center of gravity” to write an action scene. The activity is relevant here because students write an action scene as an introductory story for the biographical sketch.

Observing

To prepare to write this sketch, learn as much as you can about how the body senses gravity. In addition to the five familiar senses — sight, hearing, touch, taste and smell — you have a sense that allows you to tune into gravity. It is called kinesthesia or the kinesthetic sense, “the sense that detects bodily position, weight or movement of the muscles, tendons and joints.” Athletes and movement artists are able to tune into this sense. They are especially gifted with what Howard Gardner, in his influential book Frames of Mind, calls kinesthetic intelligence.

Conduct some research. Think about how you experience movement. As an experiment, deliberately make yourself dizzy — be careful not to bump into anything — and pay close attention to the effect. Research how the vestibular system of your inner ear works to help you maintain your balance.

You have probably heard the expressions, “I have a gut instinct” or “I just feel it in my bones” as ways of describing intuition. Can you feel gravity in your bones and joints? How do you orient yourself in space? If you close your eyes or put on a blindfold or make the room totally dark, how do you know up is up and down is down? How do you “feel” your way in the dark?

Note: “Kinesthesia” is related to and sometimes distinguished from “proprioception,” a more general sense of movement arising from sensory receptors distributed throughout the body, including the skin and internal organs. The kinesthetic sense is considered to be more localized in fibers within tendons, joints and muscle tissue, as well as in the vestibular system of the inner ear that governs balance. For the purposes of this exercise, it is only necessary to introduce students to the concept that they have a real “sixth sense” (actually, multiple senses working together) that enables them to sense the body’s position in space in relation to the pull of gravity. The point is to help students become more aware of how they perceive movement in order to understand how an athlete or movement arts performer develops and perfects this sense.

Thinking

If gravity is a law, the artists and athletes we have been talking about are some kind of law breakers. Or maybe they’re escape artists? Have a look at M.C. Escher’s famous lithograph, “Gravity.” What is going on here?

Copyright © 2004 The M.C. Escher Company - the Netherlands.

Hint: The shape is a small stellated dodecahedron with perforations. In a sense, it is a dodecahedron that “pushes the envelope.” The dodecahedron, one of the five Platonic solids, represents the universe.

What do you think Escher’s “Gravity” represents? (Possible answer: The little reptiles are attempting to escape gravity.)

Writing

To write your biographical sketch, follow these guidelines, but not necessarily in this order. Action-writing, like extreme sports, tends to break the rules:

To capture your reader’s attention, begin with a brief introductory story that describes the performer in action. Make your reader want to know more.
Discuss the performer’s background — youth, relevant education and training — as well as awards won and other achievements.
If the performer has made a profession of a sport or art, describe the career either chronologically or topically.
Describe what makes the performer unique, why they have a special understanding of how to work with gravity. If possible, interview the performer. Sometimes it can be difficult for them to explain their special magic. This is where the interviewer’s skill comes in. Remember the “journalist’s questions”!
Not surprisingly, sports writers are considered to be some of the best writers in journalism. They’ve learned to capture the essence of action. For more ideas, investigate the following examples:

Extreme Skier Teaches the Stunts, Akron Beacon Journal, Ohio, http://www.ohio.com/ or (same story) Daredevil Team Takes Skiers to Freak-Out Level and Beyond, San Antonio Express-News, Texas, http://www.mysanantonio.com/sharedcontent/registration/register.jsp.
Downhill Bicycle Racer Lives on Extreme Edge: http://www.mlive.com/news/sanews/index.ssf?/base/news-8/107090220240840.xml.

Safety Issues

Safety precautions should be taken when students experiment with making themselves dizzy or if they try some of the sports to get a feel for the topic of their writing assignment.

Troubleshooting Tips

If the news article links are no longer available, just search for new ones using a search engine such as Google. Click on the “News” tab at http://www.google.com and type “extreme sports” or “aerial dance” or the name of your favorite performer or athlete.

Assessment

Pre-Activity Assessment

Kinesthetic Experimentation: Students can experiment with orientation using a blindfold or by making themselves dizzy. Ask them to demonstrate their understanding of how the vestibular system works to help them keep their balance, and describe verbally how they experience the effects of gravity.

Activity Embedded Assessment

Graphic Concepts: In discussing Escher’s symbolic representation of gravity, have students demonstrate their understanding of how the concept is graphically depicted and why the symbol of the stellated dodecahedron is used.

Post-Activity Assessment

Action and Descriptive Writing: Evaluate the writing assignments in terms of how well the students capture the action and feeling of the sport or art form, and what makes the performer unique and exceptional.

Discussion Questions: Ask the students, and discuss as a class:

What physical forces must the performers you wrote about understand in order to excel in their sport or art form? (Possible answers: Gravity, drag, thrust, weight, lift, acceleration, air resistance, center of mass, balance, stress and strain on materials, laws of motion, friction, rotational motion, tension and compression, etc.)
If the performer you wrote about uses any tools or equipment (such as rock climbing gear or a snowboard, bicycle, etc.), how does an engineer design the tools and equipment to be safe? (Answer: Discuss how an engineer uses his understanding of math and science, and how the human body works, to design and create new sports equipment that is both fun and safe. Safety is important to prevent injuries to athletes and others.)

Activity Extensions

Learn about how pilots and astronauts deal with the effects of zero gravity. Find out what it is like to ride the “Vomit Comet.” Report your findings to the class.

Find out how the zero-gravity scenes for Apollo 13 were filmed and what the stars of the movie and the director thought about the experience. Report your findings to the class.

Write a sketch of what you think it would feel like to experience zero gravity or the opposite, the force of several “Gs” (G-force, an inertial force usually expressed in multiples of terrestrial gravity) that you would experience taking off in the shuttle, a fighter jet or whirling in a centrifuge (or some amusement park rides).

Activity Scaling

Some students may need to focus more on developing their own sense of how they experience gravity before attempting to write on the topic.
The Activity Extensions options are suitable for all levels.

References

Cirque due Soleil. Accessed January 26, 2005. (Creative and unusual dance company) http://www.cirquedusoleil.com/

Cycropia Aerial Dance. Accessed May 5, 2004. http://www.cycropia.org/

Dictionary.com. Lexico Publishing Group, LLC. Accessed May 5, 2004. (Source of vocabulary definitions, with some adaptation) http://www.dictionary.com

Gravity Games. Accessed May 5, 2004. http://www.gravitygames.com

Hart, George W. Virtual Reality Polyhedra, The Encyclopedia of Polyhedra. The Polyhedra of M.C. Escher. Accessed May 5, 2004. http://www.georgehart.com/virtual-polyhedra/escher.html

McKenzie, Jamie. Biography Maker. Bellingham Public Schools, WA. Accessed May 5, 2004. (How to write a biographical sketch) http://www.bham.wednet.edu/bio/biomak2.htm

McKissack, Patricia and Fredrick. Biography Writer’s Workshop. Scholastic Inc. Accessed May 5, 2004. http://teacher.scholastic.com/writewit/biograph/

Millman, Joyce. Dudes vs. Nature, Extreme Sports. SALON, Television, San Francisco, CA. Accessed May 4, 2004. http://www.salon.com/weekly/extreme960603.html

Momentum Machine, How ice skaters, divers and gymnasts get themselves spinning and twisting faster, Science Snacks. Exploratorium, San Francisco, CA. Accessed May 5, 2004: http://www.exploratorium.edu/snacks/momentum_machine.html

Pendulum Aerial Dance Theater. Accessed May 5, 2004: http://www.pendulumdancetheatre.org/

Roanoke Ballet Theater, Roanoke, VA. Accessed May 5, 2004: http://roanokeballet.org/

Skateboard Science, Exploratorium. Accessed May 5, 2004. http://www.exploratorium.edu/skateboarding/

Thomas, Molly. Aerial Dance Sweeps the Nation. USA Today. Accessed May 5, 2004. http://www.usatoday.com/life/2001-07-25-aerial-dance.htm

Owner: Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder

Contributors: Jane Evenson, Malinda Schaefer Zarske, Denise Carlson

Copyright: © 2004 by Regents of the University of Colorado.

Grade Level: 9 (9-11) Group Size: 2
Time Required: 120 minutes
Expendable Cost Per Group: US$13
(The breadboards, wires, wire strippers, resistors and multimeters can be re-used.) 

Summary: Students investigate circuits and their components by building a basic thermostat. They learn why key parts are necessary for the circuit to function, and alter the circuit to optimize the thermostat temperature range. They also gain an awareness of how electrical engineers design circuits for the countless electronic products in our world.
Engineering Connection: Circuits are pervasive in the modern engineered world. Most engineers have a good understanding of electricity and basic circuitry so as to better design everything from cars and houses, to cell phones and computers. Electrical engineers design the circuits that power our houses and appliances. Aerospace and mechanical engineers use their understanding of circuits to design control systems (such as anti-lock brakes), motors, amusement park rides, wave machines and space flight equipment. Other engineers design devices such as thermostats to reduce energy usage and waste.

Related subject area: Physical Science

Pre-requisite Knowledge: A familiarity with circuits in electricity, including the concepts of open and closed circuits.

Learning Objectives

After this activity, students should be able to:

Describe the relationship of a programmable thermostat to energy conservation.
Develop a model of the circuitry in a programmable thermostat.
Describe how engineers use circuit diagrams to design a circuit.
List the advantages of using a breadboard during circuit design.

Materials List

Each group needs:

1 breadboard (EXP 350 recommended, $6 from online vendors; or RadioShack for $8+; or find used breadboards)
1(or more) LM35 temperature sensor chip ($1.29 each, online from www.digikey.com; get extras in case students accidentally break one by setting up the circuit incorrectly.)
1 LM324AN operational amplifier integrated circuit ($1.69 at RadioShack)
1 9-volt battery (or have a few for the class to share)
1 9-volt battery holder (optional, or have a few for the class to share)
Ice
Ziploc bag
Thermostat Worksheet
Breadboard and Circuit Diagram Basics Handout (To download worksheets and handouts, see below).

For the entire class to share:

1 jumper wire kit (preferred since it is easier and reduces set-up time, $6.50 at RadioShack), or each group needs 2 pieces of 1-inch wire, 2 pieces of 3-inch wire, and 5 pieces of 2-inch wire and electrical tape
Small wire strippers (only needed if you are using insulated wire and not the jumper wire kit, to remove insulation at wire ends)
Multiple ¼ watt resistors of various sizes from 500 Ohm up to 10K Ohm (100-piece kit: $6.50; 500 piece kit: $13 at RadioShack)
A few multimeters to make various measurements (such as Kelvin 50LE www.kelvin.com part # 990177, $3.65)
Materials note: The breadboards, wires, wire strippers, resistors and multimeters can be re-used.

Introduction/Motivation

Who can name some things that use a circuit — or multiple circuits? (Possible answers: Cell phones, radios, televisions, computers, video games, cars, houses, buildings, calculators.) Those are all great answers. Everything that plugs into a wall outlet or runs on batteries contains a circuit in order to operate. Can anyone give me a reason why an engineer would need to know about circuits? (Answer: To be able to design and create things that use electricity to operate.) That’s right, many engineers use circuits in the design and manufacture of all the things we mentioned. More than any other type of engineer, electrical engineers primarily design using circuits. They are responsible for the design of most of the circuitry found in the everyday devices all around us, including computers and computer chips. However, many other engineers must have at least a basic understanding of circuits and how to create a simple circuit.

Today, we are going to investigate the circuit in a thermostat. Does anyone know what a thermostat is? A thermostat is a device installed in homes and buildings to regulate the temperature of an area of the building — such as a single room, a few rooms (a zone), or the entire building. Basically a thermostat works by determining the temperature in the immediate area of the sensor and converting that temperature into an electric signal. The thermostat is programmed to perform a chosen task based on that electric signal. The electric signal tells the thermostat to turn on or off a heater or air conditioner so as to change the temperature in the room.

We all want to conserve energy and make sure we are efficient in using energy in our homes, schools and places of work. Did you know that some thermostats are designed to help save energy? Most new homes and businesses use programmable thermostats that regulate the temperature of all or part of a building. These thermostats are useful in saving energy and can be programmed for many different settings. They are often set to not heat or cool a building during times when no people are using the building, since no one is present to benefit from the energy output. These times might be evenings in offices and schools, and daytimes at homes. Can you imagine how much energy we can save if we do not turn on the furnace or air conditioner when it is not needed?

Ask students to look for a thermostat in their homes or school classrooms.

Programmable thermostats can also be set to direct the heater or air conditioner to maintain a temperature range throughout the time when people are using the building; you set a low temperature and an upper temperature that is comfortable for the building’s inhabitants. If at any time the temperature at the thermostat sensor goes out of the set comfort range, the thermostat generates an electric signal to turn on either the heater to heat the room back up into the temperature range, or the air conditioner to cool the room down into the temperature range. The thermostat keeps the heater/cooler on until the temperature gets to the opposite side of the set comfort range, then sends another signal to turn it off, giving the air time to become cool or warm again before the cycle starts over.

For example, if a room goes below a set comfort temperature, the thermostat turns on the heater to warm up the room. The thermostat keeps the heater on until the temperature reaches the upper temperature boundary. Once the room temperature reaches that upper boundary, the thermostat signals to turn the heater off. Since the heater works more efficiently (saving energy) when it is not being turned on and off repeatedly, this ensures that the temperature must drop more than a degree or two before the heater is turned back on. So the benefit of having a programmable thermostat over a standard one, is that it allows you to set your own range of temperatures for the thermostat to keep the room at, rather than having the heater turn on and off repeatedly. With the more advanced programmable thermostat designs, you can program temperature ranges for different days of the week in advance, so you can accommodate differences in building use during weekdays and weekends.

As we mentioned earlier, circuits are used by different types of engineers. For example, circuits are important to mechanical engineers in the design of motors because most motors are run and maintained with a circuit. Mechanical engineers must be knowledgeable about circuits in order to effectively design and create motors to run the parts they design. Teams of engineers from with different specialties often work together to build everything from cars to roller coasters to medical instruments — devices that combine mechanical parts and electrical systems. Knowing the basic components of a circuit and how they fit and work together is important for engineers to understand if they are to design anything that uses electricity.

Today we are going to learn about the different components in a circuit and how to put them together to create a simple circuit, a thermostat. We are going to design a programmable thermostat, in which the user determines the temperature range s/he would like the room/building to remain in and the thermostat makes sure it does that in an energy-efficient way.

Vocabulary/Definitions

Breadboard:  A reusable solderless tool used to create a temporary (usually a prototype) circuit to experiment with until a more permanent circuit is created.�
Conductor:  A material that allows charges to move easily, such as copper wire.�
Electric current:  The flow of electric charge through an electrical circuit or conductor.�
Electrical circuit:  A collection of circuit elements (resistances, inductances, capacitances, etc.) connected in closed paths by conductors.�
Hysteresis:  An electric circuit that is path-dependent and, thus, has memory.�
Hysteresis band:  The difference in voltage between the turn on and turn off points in an electrical circuit using hysteresis.�
Integrated circuit (IC):  Several circuit elements that are manufactured together onto a single chip by a sequence of processing steps.�
Operational amplifier (op-amp):  An integrated circuit that contains multiple resistors and capacitors. Op-amps have many practical applications in engineering instrumentation.�
Parallel:  Two or more circuit elements are in parallel if they are connected to the same node or junction of the circuit and have the same voltage drop across their terminals.�
Resistor:  A circuit element that resists electric current and dissipates energy in the form of heat.�
Series:  Two or more circuit elements are in series if the same current flows through them.�
Voltage:  A measure of the potential energy of an electrical field to cause an electrical current in a conductor. 

Procedure

Background

Circuits have become an essential part of our everyday lives. Circuits are found everywhere — in cars, TVs, computers, phones, homes, schools, etc. Their impact on our lives is immense and much of our society would not be the same without the circuit. Most every electrical circuit contains the same basic components — resistors, integrated circuits, capacitors and inductors. Each of these components performs a certain task (sometimes different components are combined to do the job of one of the other components) and are used by most engineers, especially those working with electricity or products that use electricity.

Thermostats are useful devices to regulate the temperature of a room, area or an entire building. They work by using a temperature sensor — generally an electronic chip designed to change its resistance depending on the temperature. As the temperature of the chip changes, the resistance of the chip changes and alters the voltage drop across the chip. The chip is internally calibrated to produce a linear relationship between the temperature and the voltage output of the sensor. After the sensor determines the temperature, the resulting electrical signal (output voltage) is sent into another portion of the circuit designed to interpret the incoming voltage and select an outcome based on the signal. This part of the circuit can be performed in many ways; however, the least complicated way is to use an operational amplifier (op amp).

Using an op amp permits the introduction of hysteresis into the circuit — or memory. In this activity, students take the output signal from the sensor and compare it to a predetermined voltage that is manually set. If the voltage from the sensor measures lower than the voltage the students set, indicating that the temperature sensor is reading a temperature that is colder than what we want it to be, the heater (an LED) turns on to “warm up” the room. Once the heater (LED) turns on, the hysteresis of the op amp forces the heater to stay on until the voltage goes above the second or high voltage set in the desired comfort range. This keeps the thermostat from rapidly turning the heater on and off if the temperature is hovering around the desired initial temperature. By forcing the heater to stay on until the second voltage, the circuit demonstrates path-dependence, which means that it remembers where it has been and uses that to inform what it will do next. It will not turn off after going above the low-set voltage because it “knows” that it just recently went below that mark. It forces the heater to stay on until the second voltage mark is passed.

The circuit the students create contains a LM35 temperature sensor, which has a linear relationship between the temperature of the sensor and the output voltage; the relationship is 10mV for every degree Celsius. Therefore, at room temperature (~20-23 °C), the LM35 should have an output voltage of 200-230mV. As the temperature rises or falls, the output voltage rises or drops 10mV for each degree of temperature change.

Before the Activity

If using insulated wire, cut it into sections for each group.
Make copies of the Thermostat Worksheet and the Breadboard and Circuit Diagram Basics Handout.

With the Students

Divide the class into groups of two or three students each.
Distribute the materials to each group along with the worksheet and handout.
If using the insulated wire, have students strip about ¼ to 3/8 of an inch from both ends of each of the wires.
Have students set up the circuit as shown in Part 1 of the worksheet. Reference the handout for additional information, especially clarification of the circuit diagram symbols and breadboards parts.
Have students turn on the multimeters and set them up to measure voltage in mV.
Have students place the battery in the battery holder, or tape the ends of the two pieces of 3-inch wire to both the positive and negative terminals of the battery.
Connect the wire coming from the positive terminal (denoted with a + on the side of the battery that the positive terminal is on) to the power row on the breadboard.
To complete the circuit, connect the wire coming from the negative terminal (denoted with a (-) on the side of the battery) to the ground row on the breadboard.
Have students complete the circuit check part of the worksheet.
Have students complete the modeling the circuit part of the worksheet.
Have students use multimeters to measure the voltage from the output of the temperature sensor and record the value on the worksheet .
Have one student in each team continue to measure the voltage from the output of the temperature sensor while the others cool the temperature sensor using a Ziploc bag containing ice.
The light should turn on when the temperature (voltage) reaches the low point of our set temperature range. Have students record this value of the voltage on the worksheet.
After the light comes on, have students warm the temperature sensor by blowing on it or pinching it between two fingers.
As the upper temperature (voltage) of our range is reached, the light should turn off. Again, have students record this voltage value on the worksheet.
Have students work out the redesigning the circuit part of the worksheet.
Have students calculate on their worksheet the new voltages corresponding to the new temperatures.
Have students identify which resistors must be changed for their new design and have them change them to coincide with the new cut-off points. (It may be necessary to connect resistors in series or parallel to achieve desired voltages. Also, you may not be able to get the exact resistance the students calculated; if this is the case, have them get as close as possible and note it on the worksheet.)
Have students model the new circuit by repeating steps 10-15 with the new, optimized circuit (Part 5 on the worksheet).
Have students complete the analysis part of the worksheet.
Conclude by leading a class discussion to review the worksheet answers.
To further test students’ comprehension, ask them how they would make the thermostat hysteresis work in reverse, so that the circuit turns on at the higher temperature and turns off at the lower temperature — like an air conditioner, instead of a heater.

Worksheets and handouts:

Thermostat Worksheet
Thermostat Worksheet
Thermostat Worksheet Answers
Thermostat Worksheet Answers
Breadboard and Circuit Diagram Basics Handout
Breadboard and Circuit Diagram Basics Handout
(To download these documents, go to www.teachengineering.org, click on browse, then on activities, then search for Designing a Thermostat).

Safety Issues

Working with electricity is always dangerous. To make sure that a component does not overheat, remind students to double-check their circuit with the circuit diagram and image provided on the worksheet before connecting the circuit to the battery.
Attention to detail is important. Remind students to take care to make sure the components are placed where they should be. The wrong connections to ground and/or power can cause these chips to overheat, smoke, and (potentially) become permanently damaged.

Troubleshooting Tips

Make sure students do not leave the battery connected to the breadboard if they are not actively taking a measurement, debugging or observing the circuit. Keeping it unconnected most of the time prolongs the life of the battery and ensures that the circuit components do not get too hot by being “left on” for a while.

If a team’s circuit is not working, disconnect the breadboard wires coming from the battery and double-check the circuit diagram and circuit. Make sure that the pins from the LM35 and LM324AN are connected and oriented correctly. If everything looks good, reconnect the battery and debug the circuit using the multimeter. Check the input and ground pins of the temperature sensor and the LM324AN to make sure they are connected properly. The multimeter should read 9 volts (or close to that) for the input on the temperature sensor; the ground for both should read zero volts (or close to that). The input of the LM324AN should be the same as the output of the temperature sensor. Also check the connections to the LED; make sure there is an input when there should be one, and that the ground pin of the LED reads zero volts.

LEDs can easily burn out if they are left on too long, or if too large of a current is sent through them. This is why the output from the LM324AN goes through a resistance before reaching the LED. If a circuit is not working, and everything else seems to be in the correct place, try a different LED.

Make sure that none of the resistors touch another resistor, which makes those two resistors in series and thus changes the value of the resistance, and consequently the voltage going through that section of the circuit.

Assessment

Pre-Activity Assessment

Class Discussion Question: Ask the students and discuss as a class:

Why might it be a good idea to be able to control at which temperatures a heater and/or air conditioner turns on and off?

Activity Embedded Assessment

Worksheet: Have students complete the activity worksheet; review their answers to gauge their mastery of the subject.

Post-Activity Assessment

Worksheet Discussion: Review and discuss the worksheet answers with the entire class. Use students’ answers to gauge their mastery of the subject. In Reverse: Have students either brainstorm or research ways to allow the thermostat hysteresis work in reverse, so that the circuit turns on at the higher temperature and turns off at the lower temperature — like an air conditioner, instead of a heater. To do this, the students would rewire the circuit to turn on and off at different temperatures.

Activity Extensions

Have students research hysteresis. Find out what it means, how this circuit uses hysteresis and other examples of hysteresis.

Have students research where else hysteresis shows up. Have them prepare a paragraph describing the phenomenon they discover and how it displays hysteresis. Also have them compare it to the circuit they have just built. How are they similar? How are they different?

Activity Scaling

For students with a better understanding of circuit analysis, have them research the formulas used to determine the resistances needed to set the on/off points (Kirchhoff’s voltage and current laws, Ohm’s Law, etc.).

Owner: Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder. Contributors: Tyler Maline, Lauren Cooper, Malinda Schaefer Zarske, Denise W. Carlson.

Copyright: © 2007 by Regents of the University of Colorado

Grade Level: 4 (3-5) Group Size: 3
Time Required: 45 minutes
Expendable Cost Per Group: US$ .50

Summary: In this activity, students learn about their heart rate and different ways it can be measured. Students construct a simple measurement device using clay and a toothpick, and then use this device to measure their heart rate under different circumstances (i.e., sitting, standing and jumping). Students make predictions and record data on a worksheet.

Engineering Connection: Engineers help doctors by developing devices to detect heartbeats such as stethoscopes and machines that monitor the heart rate of a person when they are sick or exercising. NASA engineers used the same technology that the fuel pumps in the Space Shuttle uses to help design a tiny ventricular assist pump to help pump blood through the body and regulates a heartbeat. There are many pumps that have been designed by engineers that mimic the pumping action of the heart in the human body.
Related Subject Area: Biology

Pre-requisite Knowledge: A basic understanding of the human heart and its role in the circulatory system would allow students to get more out of the lesson.

Learning Objectives

After this activity, students should be able to:
Explain the mechanics behind a pulse.
Describe how to measure a heart rate and what affects heart rate.
List the importance of medical equipment designed by engineers to locate and monitor heart rates.

Materials List

For each group:

For attachments, click on The Beat Goes On in the “browse activities” section of TeachEngineering website.

Attached Heartbeat Worksheet (one per group) and Heartbeat Math Worksheet (one per student)
A 1” cube or ball of modeling clay (any color)
1 round toothpick
Stopwatch

For entire class to share:

Stethoscope (optional)
Empty 1-gallon milk/water jug (optional)

Introduction/Motivation

Have you ever heard your heart beating? The doctor listens to your heartbeat when you have a check-up or other visit. What is that sound the doctor is hearing? What exactly makes your heart beat? Well, the heart creates a beat because it works like a pump. The heart is similar to a water pump that brings water to the sinks all around your house. Instead of water, however, the heart pushes blood through your body in blood vessels. This pumping action causes high-pressure power surges of blood that travel from the heart through the body, in a pulse. Each power surge repeats itself almost every second. In order to detect the power surge, or feel your pulse, a vessel carrying the pumped blood, such as an artery, must be near the surface of your skin. Some vessels are better than others for feeling your pulse; however, we can find pulse points (locations where a vessel is close to the surface) all over the body for measuring heart rates. Some examples of good pulse points include: the radial artery in the wrist, the anterior tibial artery on the front of the ankle, the popliteal artery in the back of the knee, the femoral artery in the groin, the brachial artery in the inside of the elbow, and the carotid artery in the neck. Don’t worry, you do not need to remember the names of all these points, but it is good to know where they are located.

The lub-dub sound you are hearing when you listen to your hearth is the sound of the valves in your heart opening and closing. (“Lub” is when the two upper chambers, or the atriums, are pumping the blood into the ventricles, and “dub” is when the ventricles are pumping the blood to either the lungs or the body.) The harder your body is working (i.e., exercising), the faster your heart pumps blood through your body. Size is another thing that affects how fast the heart beats. Very large mammals can have a heartbeat of 20 to 30 BPM (beats per minute) and very small animals can have heart rates exceeding 500 BPM. The average human heart rate is around 60-100 BPM (resting), which means it beats more than 30 million times per year and about 2.5 billion times in a 70-year lifetime.

The pulse is used as a guide for the health of the heart, and detecting irregularities helps to predict if arteries are clogged (which may lead to heart attacks). If an ambulance is called to help someone who is injured, the medical technicians immediately check the person’s pulse to see how they are doing. If the pulse is too fast or too slow, it can be a sign that something is very wrong and can determine the next course of action. Engineers help doctors by developing devices to detect heartbeats such as stethoscopes and image devices (little cameras) that allow doctors to see clogged blood vessels. Engineers also develop machines that monitor the heart rate of a person when they are sick or exercising.

In this activity, we test our heart rates by counting our pulses after certain activities. Then, we will think like engineers to come up with ideas on how to monitor how healthy our heart is using our heart rate.

Procedure

Before the Activity

Gather all activity materials.
Print out the Heartbeat Worksheet (one per group) and Heartbeat Math Worksheet (one per student).
Prepare an overhead of the locations of the pulse on the body.

With the Students

Ask students if they can see their heart beating. Discuss with students that our heartbeat can be heard and sometimes felt, but not always seen without some assistance. Engineers design special instruments to help doctors monitor the heart rate and pulse of patients in a hospital.
Divide students in groups of three: one person will be a recorder, one person will be a timer and the third person will be a pulse measurer.
Have students predict how many heartbeats they think will occur in one minute as they listen to their pulse. They should record this number on their Heartbeat Worksheet.
Demonstrate how to find a pulse on the left side of the neck.
Have students practice until they are able to feel the pulse and count accurately.
Have students count their pulse for one minute while sitting and record it in the proper section of the record chart. (Note: the teacher may want to time one minute, having all groups begin and end their counting at the same time.)
Pass out activity materials to each group.
If not already flat, flatten the bottom of the clay.
Insert the toothpick into the clay.
Place 1 group member’s wrist, palm side up, on the table, while the person is sitting.
Place the clay on the wrist, and move the clay around on the palm side of the wrist until the toothpick starts to vibrate back and forth.
Count the number of vibrations that the toothpick makes in one minute.
Have the recorder write the data on the Heartbeat Worksheet observation chart and label the units as BPM (beats per minute).
Repeat steps 10-13 with each member of the group.
Ask students if their own heart beats at the same rate all the time. Ask them to record their answer on their worksheet.
Have students check their pulse one at a time, using their pulse meter after each of the following activities and record the results on their observation chart.
Count after standing for one minute.
Count after jumping in place for one minute.
Ask students to share their findings with the class. When was their heartbeat the fastest? The slowest?
(Optional) Explain how the stethoscope is used. Let everyone listen to his or her heartbeat. Be sure to clean the earpiece after each use (alcohol wipes work well). Discuss what students heard and record comments on board. Talk to the students about how engineers design medical devices such as stethoscopes.
When might you want to know if your heart is beating too fast? How about too slow? What have you learned today that would help you design a heart monitor? Engineers design instruments such as heart monitors to help track the heart rates of patients in hospitals or ambulances. Have students come up with ideas on how to monitor how healthy our heart is using our heart rate. (If time, have them sketch their ideas on paper.)
Have students complete the Heartbeat Math Worksheet to calculate the number of times their heart pumps in a day or year.

Attachments (See The Beat Goes On  in the  Browse Activities section of www.TeachEngineering.org)

Heartbeat Worksheet (pdf)
Heartbeat Worksheet (doc)
Heartbeat Math Worksheet (pdf)
Heartbeat Math Worksheet (doc)
Troubleshooting Tips

Make sure that students are checking their pulse correctly. It may help to demonstrate process to the students first. Students must keep their wrist still to see the pulse movements with the toothpick. If they move their hand around a lot, they may get a false reading.

Students should get a number between 70 – 140 beats per minute for each trial.

Some students may have a weak pulse. Try to move the pulse meter around enough to get the toothpick to move. If this does not work, try to measure the pulse from the neck. You can also pick the person in the group who has the strongest pulse to use the pulse meter.

Assessment

Pre-Activity Assessment

Class discussion: Solicit, integrate and summarize student responses.

Can you see your heart beating? How do you know your heart is beating? Does the rate of your heart beat ever change?
Prediction: Have the students predict their heart rate when they are sitting still and record predictions on the board.

Activity Embedded Assessment

Worksheet: Have the students record measurements and follow along with the activity on their Heartbeat Worksheet. After students have finished their worksheet, have them compare answers with their peers.

Post-Activity Assessment

Prediction Analysis: Have students compare their initial predictions with their test results, as recorded on the worksheets. Ask the students to explain why their prediction was correct or incorrect. Discuss reasons why their predictions were either too high or too low.

Math Worksheet: Have students work through the Heartbeat Math Worksheet to calculate their heart rate. Students should answer the challenge questions on the bottom of the data sheet and discuss. If available, bring in an empty gallon of milk or water to show how much blood is pumped in 1 minute (1.7 gallon).

Activity Extensions

Create a large table of data with the heart rates of the entire class.

Repeat this activity with the students taking their pulse in other areas of the body such as, wrist and underarm.

Repeat the procedure for even more various activities; i.e., running in place for one minute, eating lunch, first thing in the morning, at the end of the school day, etc. Compare this data to data recorded earlier.

Have the students take the heartbeat of other family members (possibly even pets) and compare the results to their own for homework.

Activity Scaling

For older students, discuss what causes the heart rate to increase: stress, exercise, clogged blood vessels. Discuss the link to blood pressure. Blood pressure equals the Cardiac output multiplied by the total peripheral resistance. Cardiac output is heart rate multiplied by stroke volume, or the amount of blood pumped with each beat. Total peripheral resistance is a measure of the blood vessels resistance to flow.

For younger students: It may be easier to time one minute as a class and have the students start and stop counting together. Also, the math worksheet may be best as a class activity on the board. The challenge questions could be given to advanced math students.

Owner: Integrated Teaching and Learning Program and Laboratory, University of Colorado at Boulder

Contributors: Jessica Todd, Sara Born, Denali Lander, Malinda Schaefer Zarske, Janet Yowell

Copyright: © 2004 by Regents of the University of Colorado

Summary: After a discussion about what a parachute is and how it works, students will create a parachute using different materials that they think will work best. The students will test their designs, which will be followed by a class discussion (and possible journal writing) to highlight which paper material worked best.
Engineering Connection: Aerodynamics and fluid flow concepts are used by engineers to design planes, parachutes and ships. Accounting for drag is an important aspect of these designs - engineers redesign the shape and materials used to get better results.

Learning Objectives

Techniques for designing a parachute that falls slowly.
How to determine which type of material works best by testing different options.
How air resistance plays a role in flying.

Materials List

Tissue paper
Napkins
Construction paper
Newspaper
Paper towels
String
Tape
Weights (i.e. washers)

Introduction/Motivation

What is the purpose of a parachute? What is the role of a parachute in skydiving? Imagine you are jumping out of a plane 10,000 feet in the air. What type of material would you want your parachute to be made out of and what size would you want it to be? The design of a parachute is extremely important, especially in an extreme sport like skydiving because someone’s life is dependent on the parachute functioning properly. Engineers must test the materials and design of a parachute to ensure that it will open properly and be strong enough to withstand the air resistance needed to slow the skydiver down enough to a safe landing speed.

Procedure

Background:

A parachute is an umbrella-shaped device of light fabric used especially for making a safe jump from an aircraft. Due to the resistance of the air, a drag force acts on a falling body (parachute) to slow down its motion. Without air resistance, or drag, objects would continue to increase speed until the object hit the ground. The larger the object, the greater its air resistance. Parachutes use a large canopy to increase air resistance. This gives a slow fall and a soft landing.

Recommended Resources:

http://www.parachutehistory.com/

http://www.glenbrook.k12.il.us/gbssci/phys/Class/newtlaws/u2l3e.html

http://www.grc.nasa.gov/WWW/K-12/airplane/falling.html

Directions

Buy or gather available materials
Discuss with the class what a parachute is and how it works.
Have each team brainstorm characteristics of a good parachute, document their thoughts and sketch their design before construction begins.

Parachute Construction

Cut a circle from the paper chosen (or test another). Make a hole in the center of the shape.
Cut six pieces of equal-length string and tape them at equal distances around the edge of the shape.
Tape the other ends of the string to the weight.

To test the parachute, go outside and drop it from a specific height to see if it flies slowly and lands gently.

Investigating Questions

What type of paper is the best material to make a parachute? Why?
What materials did not work well? Why?
What changes could you make to improve your design?

Activity Extensions

Using the paper material that worked the best, do the same activity testing the size of the parachute. Have students test circles with different radii to find the optimal size.
Try parachutes with and without holes in the top and different sized holes.
Make parachutes out of different materials: plastics, cotton, nylon.
Have a competition to find a design that can land a toy vehicle most gently.
Owner: Center for Engineering Educational Outreach, Tufts University

Copyright: © 2005 by Worcester Polytechnic Institute.

Group Size: 1
Time Required: 100 minutes
One 50-minute class period to introduce concepts; homework time to write journal and blogs; additional class time to prepare the play.

Summary: Students read news reports and first-person accounts to imagine what it would be like to be in a blackout in a large city. They follow news reports as if the event were unfolding in real-time and keep weblogs or journals of their experience as they imagine it, taking on different roles of people who live in the city or commute there to work. They use their journal accounts to create a play or screenplay that depicts what the August 2003 blackout was like for the people in the U.S. and Canada who experienced it. Although this activity is geared towards fifth-grade and older students and Internet research capabilities are required, it could be easily adapted for younger students.
Engineering Connection: One of the biggest concerns for power company engineers is making sure everyone gets electricity when they need it. Detailed regional grid maps of power plant locations and distribution systems throughout the U.S. show the real-time demand and load changes by buildings and equipment as their connections to power plants are turned on and off. Sometimes damaged power lines cause interruption in power or blackouts. The regional grid maps help to determine where the damaged occurred and develop alternative routings so that electricity continues to be delivered to power companies’ customers.

Subject areas: Physical Science, Science and Technology

Prerequisite knowledge: A basic understanding of electrical energy (charge, voltage, current, resistance), and its pervasiveness in our way of life (lights, heat, safety, appliances, computers, medical equipment, transportation, entertainment).

Learning Objectives

After this activity, students should be able to:

Use a full range of strategies to comprehend technical writing.
Write stories, letters and reports with greater detail and supporting material.
Choose vocabulary and figures of speech that communicate clearly.
Draft, revise, edit and proofread for a legible final copy.
Apply skills in analysis, synthesis, evaluation and explanation to their writing and speaking.
Incorporate source materials into their speaking and writing (for example, interviews, news articles, encyclopedia information).
Write and speak in the content areas using the technical vocabulary of the subject accurately.
Recognize stylistic elements such as voice, tone and style.
Recognize, express and defend a point of view orally in an articulate manner and in writing.
Apply skills in analysis, synthesis, evaluation and explanation to their writing and speaking.

Materials List

Paper and pencils
Access to the Internet (highly recommended, but optional)
Video tape recorder (optional)

Introduction/Motivation

What would it be like to live without electricity? What would happen if an entire major metropolitan region was without electricity? That is exactly what happened during the August 2003 blackout in the northeastern U.S. and Canada. How would it feel if you were a commuter stranded in the city just as the rush hour was beginning? What would you do? What if you were stranded in a subway? Or, trapped in an elevator? Or, on a roller coaster? What if you lived in the city itself and had to make your way home through the streets and into your building in the dark and with elevators out of service? What if you were a shopkeeper concerned about looting? Or, a restaurant owner who had no power to keep food refrigerated or run cash registers, and suddenly had lots of hungry stranded customers? How would you keep medical equipment working for hospitalized people? What if you were a police officer or a fire fighter? How would you keep people calm and prevent crime as night fell? What if you were the mayor of the city? What information would you need to give the citizens to help keep them calm and safe? Today, you will follow news reports of the event and imagine yourself playing a role in the unfolding drama.

Vocabulary/Definitions

Blackout: Lack of illumination caused by an electrical power failure; the failure of electric power for a general region.

Blog (weblog): A personal website that provides updated headlines and news articles of other sites that are of interest to the user, also may include journal entries, commentaries and recommendations compiled by the user; a shared online journal at which people can post diary entries about their personal experiences and hobbies.

Cascading blackout: A blackout that occurs when one power failure causes a system overload that leads to a second failure and a third and so on, affecting a wide region (as happened in the August 2003 blackout).

Power grid: A system of high-tension cables by which electrical power is distributed throughout a region.

Real time: 1. The actual time that it takes a process to occur; information is updated in real time. 2. (computer science) The time it takes for a process under computer control to occur.

Procedure

Before the Activity

This is both an individual and class activity. Make the Internet available for student information gathering, or gather photocopies of newspaper and magazine articles about the August 2003 blackout. Students follow the news reports of the event and imagine themselves playing a role in the unfolding drama.

With the Students

In this activity, you will gather information about the blackout that occurred in August 2003 in the northeastern U.S. and Canada. You will take on one of the following roles (or another that you might imagine) and record events in a blog or journal, as if they were unfolding in real time:

Stockbroker, who works in the city and lives in the suburbs
Shopkeeper
Restaurant owner
Father or mother, whose child is at an after school activity when the blackout occurs
Nurse, caring for patients in a hospital
Police officer
Firefighter
News broadcaster, who lives in the city (find out how Diane Sawyer got home during the blackout)
Mayor of New York City
Commuter, stranded in the subway
Young woman or man, on the roller coaster at Coney Island with boy/girlfriend
Pregnant woman, caught on an elevator
If your class does not have classroom weblog (blog), see this New York Times article for ideas: (free registration required to access this news article)

http://www.nytimes.com/2004/08/19/technology/circuits/19blog.html?th. The class will combine these accounts to weave together a story of the blackout to present in the form of a play or screenplay (script for a movie) that you video tape.

Observing

To get yourself into the scene, read as much as you can about the August 2003 blackout. Start with the news articles listed in References section, or find others on the Internet. Don’t limit yourself to those articles, however. Learn as much as you can by doing your own research, just as any good playwright, director or actor does. To make sure the events of your drama follow a logical progression, use newspaper accounts to work out a timeline from the moment the power goes out in New York City until it is restored.

Thinking

As you do your research, think about these questions: Besides New York City, what other major cities were affected? (Answers: Cleveland, Ohio; Detroit, Michigan; Toronto and Ottawa, Canada.) Besides the power outage itself, what other concern would New York citizens be expected to have? (Possible answer: Terrorism) What did the mayor do to address the citizens’ concerns? (Answer: The possibility of a terrorist attack was dismissed 20 minutes into the blackout.) Why was such a large area affected? What is a cascading blackout? How many power stations went offline? (Answer: We will learn more about the power grid in another activity, but the concept of an interconnected power grid should be introduced briefly here. See that activity, The Grid, for background on the power grid.)

While the electricity was out, computers in the area of the blackout did not work, of course, but access to the Internet was slowed in areas not directly affected by the blackout. Why was that the case? (Answer: Servers in the area of the blackout were affected and could not respond to requests to view pages. The Internet itself is an interconnected grid, which is why it, too, is vulnerable to terrorism.) What were some early theories advanced for why the blackout happened? (Answers: Lightning strike, computer virus and terrorism were all suggested and ruled out quickly.)

What was the real reason for the blackout? (Answer: A government task force found no one cause for the cascading power outage. Some point to a series of transmission line and large power plant failures in the Midwest in the hours before the outage. Contributing factors include process and communication failures, human error, overall fragility of our electricity infrastructure system, and lack of power plant capacity.)

Writing

You can structure your play in a couple of different ways. It can have an episodic structure, in which one scene simply follows another with no real connection between scenes. Or you can have a unified structure, perhaps built around a central character who plays a role in every scene and moves the action along, or with a central theme that unites the action, or a central motif, an image that suggests meaning without stating it directly.

A police officer might be a good central character because a police officer could conceivably play a role in many different scenes and logically interact with many other different characters. A central motif might be an object that is passed from character to character in a drama, like a cell phone that represents communication or a bicycle that represents transportation. A central theme might be “resourcefulness” or the different ways people react emotionally to having their normal routine disrupted. A good way to unify your drama might be to demonstrate “random acts of kindness” performed by all the characters in individual ways.

Troubleshooting Tips

Since Internet links to news articles can quickly become outdated, do your own keyword search for current articles by entering one or more terms (blackout, power outage, August 2003, northeast power outage) at http://www.google.com/ under the “News” tab.

As an alternate class activity, assign each student a different role of all the types of people who might find themselves in a blackout. Have them write a one-page essay expressing their point-of-view and opinions of the blackout. Conclude by having each student read their story to the entire class.

Assessment

Pre-Activity Assessment

Call-Out Questions: Use call-out questions to reinforce basic concepts as they are introduced during the Observing activity.

Activity Embedded Assessment

Call-Out Questions: During the Thinking discussion, test students’ understanding of the events, grasp of the timeline and details that make their play interesting.

Post-Activity Assessment

Writing/Performance: The students’ journal and play demonstrate their understanding of the concepts.

Activity Extensions

Do some historical research by comparing the 2003 blackout with the 1965 blackout. See the Blackout History Project, http://blackout.gmu.edu/. html.

Also see a CNN.com story, Major Power Outage Hits New York, Other Large Cities, August 14, 2003, http://www.cnn.com/2003/US/08/14/power.outage/index.html. At the end of the article, read a comparison of three previous blackouts, including the Great Northeast Blackout of 1965. Read Central Maine Power’s story on the Great Northeast Blackout of 1965, including a letter from President Lyndon B. Johnson, http://www.cmpco.com/YourHome/default.html

Look at the before and after satellite images of the August 2003 Blackout (see Figure 1). The light is obviously considerably less in the “after” photo, but there is still some light. Investigate why. Why is the blackout not total in the affected areas? (Answer: Some businesses and hospitals have backup systems or distributed energy [DE] systems and generate their own power.

Activity Scaling

Depending on ability level and available time, students can record events in their blogs or journals from a character’s point-of-view or they can write a simple skit or more complex play or screenplay.

Owner: Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder

Contributors: Jane Evenson, Malinda Schaefer Zarske, Denise Carlson

Copyright: © 2005 by Regents of the University of Colorado.

Grade Level: 7 (6-8)

Summary: Students will build a wire circuit and pass a paperclip through the maze, trying not to touch the wire. Touching the wire with the paperclip will cause the circuit to close, which will activate the indicator.

????????Engineering Connection: We use circuits every day in household appliances from computers and radios to ovens and refrigerators. One of the most important circuits we use each day is that of a light bulb. In this activity, students will gain a basic understanding of an electrical circuit - the basis of electrical engineering.

Learning Objectives

To understand what causes electrical circuits to work

Materials List

• 5 meters of stripped wire
• 1 pair of wire cutters
• 1 battery
• 1 noise maker/light
• 1 metal paper clip

Introduction/Motivation

Electrical engineers work with anything that carries electricity. Computers are primarily designed by electrical engineers. In this workshop we will explore the concept of closed circuits. We will use the materials given to design a maze. The object is to not touch the wire with the paper clip as you pass it over the maze. When you touch the maze with the paperclip a noise or light will signal that the circuit has been closed.

Procedure

1. Assemble the wire in the desired shape leaving a strand of wire on each end of the maze.
2. Take one end of the wire from the maze and connect it to the battery.
3. Take the other end and thread the paperclip onto the wire and then connect with wire to the noise maker/light.
4. Connect the battery to the noise maker/light.
5. Move the paper clip around the wire, trying not to touch the wire.

Investigating Questions

1. Could you set this up differently and still have it work?
2. Could you do this with wire that was covered?

Assessment

Use investigating questions as an assessment tool by asking students to write up possible options/solutions as homework.

Owner: K-12 Outreach Office, Worcester Polytechnic Institute

Copyright: © 2005 by Worcester Polytechnic Institute
including copyrighted works of other educational institutions; all rights reserved.

Summary: In this scenario-based activity, students design ways to either clean a water source or find a new water source, depending on given hypothetical family scenarios. They act as engineers to draw and write about what they could do to provide water to a community facing a water crisis. They also learn the basic steps of the engineering design process.
Engineering Connection: Water sources are increasingly becoming polluted by human-made and natural contaminants. In addition, water sources are beginning to retain less and less water for people’s’ daily needs. Engineers have long recognized this as a growing problem, and they are being called upon to design better ways to manage our water resources and develop advanced technologies to clean our water and to preserve and protect our water sources. Finding solutions to meet a community’s water needs requires that engineers take into consideration the region’s climate as well as the available natural and human resources.

Learning Objectives

After this activity, students should be able to:

•      List several real scenarios that involve threats to community water resources.
•      Explain the importance and challenges involved in cleaning water for human use.
•      Describe how engineers are involved with finding and cleaning water.

Materials List

Each group needs:

•      One large sheet of paper, poster board or chart paper
•      Colored pencils or markers
•      One water problem scenario from the Family Scenario Note Cards

Introduction/Motivation 

What would happen if you woke up tomorrow, turned the water tap on for a drink, and dirty brown water came out? How about if you turned the water faucet and no water came out? What would happen if, at home this evening, people came by your house and said that you should not drink your water because a terrible contaminant  (pollution) had been found in it? What if people said you had to limit your water use because we were running out? What would you do? This all sounds really bad, but it actually happens!

All over the world, problems of water quality and quantity are very real. In Bangladesh, a contaminant known as arsenic was found in many water sources. Arsenic in very small amounts causes skin and internal cancers. Yikes! You don’t want to drink arsenic! In other parts of the world people must walk very long distances everyday to get water because it is not piped to where they live. They do not have water faucets or wells. Sometimes their trek to get water is tiring or dangerous. In the U.S., after Hurricane Katrina, water supplies in parts of New Orleans were too dirty for drinking. The water was filled with dirt and sand. You don’t want to drink water filled with dirt, do you? Also, regions in the southwestern U.S. have been having a water shortage for years. There just is not enough water for everyone who needs it.
How about getting water in the first place? What type of climate do you live in? Do you know the source of your drinking water? Often, people collect precipitation. In Asia and Africa, communities collected rainwater as a source of fresh water. Rainwater is still collected today to use for drinking and daily water use (see Figure 1).

What do we do when these water problems occur? Environmental engineers, water resource engineers, chemical engineers and many other people work on ways to solve these problems. Engineering teams and companies often develop new technologies to clean up dirty or polluted water, and collect and conserve our water sources. Today we are going to act as engineering companies, looking at different situations in which water sources are threatened. We will even design ways to handle specific water problems. Are you ready?

Procedure

Background Information: Engineering Design Process

Engineers design and build all types of structures, systems and products that are important in our everyday lives. The engineering design process is a series of steps that engineering teams use to guide them as they solve problems:

1. Understand the need: What is the problem? What do I want to do? What are the project requirements? What are the limitations? Who is the customer? What is the goal? Gather information and research what others have done.
2. Brainstorm and design: Imagine and brainstorm ideas. Be creative. Explore, compare and analyze many possible solutions. Select the most promising idea.
3. Plan: Draw a diagram of your idea. How will it work? What materials and tools are needed? How will you test it to make sure it works?
4. Create: Assign team tasks. Build a prototype (model). Does it work? Talk about what works, what doesn’t and what could work better.
5. Improve: Talk about how you could improve your product. Make revisions. Draw new designs. Make your product the best it can be.

Engineers use their science and math knowledge to explore options and compare many ideas. This is called open-ended design because when you start to solve a problem, you don’t know what the best solution will be. The process is cyclical and may begin at, and return to, any step.

The use of prototypes (model), or early versions of the design helps the design process by improving the understanding of the problem, identifying missing requirements, evaluating design objectives and product features, and getting feedback from others.

Engineers select the solution that best uses the available resources and best meets the project’s requirements. They consider many factors: Cost to make and use, quality, reliability, safety, functionality, ease of use, aesthetics, ethics, social impact, maintainability, manufacturability.

Before the Activity

•     Gather materials.
•     Make copies of the Family Scenario Note Cards (contains five different scenarios) and cut out the water problem scenarios.

 With the Students: Design

Scenes shows water sources in four different climates: rain and river in a forest, a tropical beach, a desert oasis, an alpine lake.

1. Divide the class into teams of two or three students each. Tell the students that each team represents a water engineering company that helps solve the problems of families or communities that need clean drinking water.
2. Conduct the pre-activity assessment activity described in the Assessment section.
3. Write the steps of the engineering design process on the board. Review with students how all engineers like to solve problems to make things better. These are the usual steps they take when working on a problem, just like what they are doing today.
4. Hand each team a water problem scenario.
5. Allow each team time to brainstorm a way to fix the problem. Let them know that any design or method is fine, except they must be realistic for their situation. Consider the resources and limitations of the climate of their scenario. Encourage them to be creative! As needed, guide and evaluate them with questions provided in the Assessment section. Have teams draw their engineering method(s) to fix their water problem scenarios on large paper using markers or colored pencils. Ask students to label the parts of their designs and be as detailed as possible. Point out how designing, planning and creating a model are steps in the engineering design process.
6. Have students decide on a name for their engineering company and write it on the top of their design drawing.

With the Students: Presentation

1. Have each engineering team present its design to the class, and explain how it will solve the family’s water problem.
2. Conclude by leading a class discussion. Why do we need clean water? Is finding water different in different climates? What are the types of real-world situations that can threaten our community water resources? What are the problems we might have in trying to clean dirty water so it is okay for human use? How do engineers help us? (Possible answers: Water collection, water treatment.) What are the steps of the engineering design process? Any time you are solving a problem or building something, think about the engineering design process. It helps you think through all aspects of a problem to find a good solution. When you saw other team presentations, did you get any ideas that would improve your design?
3. Conduct the post-activity assessment activity described in the Assessment section.

Attachments

Family Scenario Note Cards (doc)
Family Scenario Note Cards (pdf)

Troubleshooting Tips

When coming up with design solutions, make sure students use realistic approaches and think about the climate conditions. Some teams made need a little encouragement to find a solution.

Assessment

Pre-Activity Assessment

On Your Toes Brainstorming: In small groups, have students engage in open discussion. Remind students that no idea or suggestion is “silly.” All ideas should be respectfully heard.

Assign each team a particular climate (tropical, coastal, alpine, desert, etc.). For two minutes ask them to brainstorm and write down different water sources for their particular climate.
Disaster strikes! After two minutes, go around to each group and tell them that they could no longer get water from the major water source they listed! Ask them to brainstorm what they could do if this water source was removed.

Activity Embedded Assessment

Group Questions: During the activity, visit each group and ask the following questions:

1.     How does this design relate to the climate in which your family or community lives?
2.     Why did you choose this design?
3.     What sort of power or energy needs would your design need? (For example, if the design involves moving or pumping the water, do they need a pump? What will power the pump? Batteries or electricity, etc.)

Post-Activity Assessment

Re-Engineering: Have each team switch their original family scenario note card with another group. Ask students to evaluate their current design for this new scenario. Have students discuss if and why their design would or would not work in this different situation in a different climate. Ask them to think about what they could do to make it work for the new conditions.

Activity Extensions

Have other student engineering teams in the class evaluate and offer suggestions for improvements to each design.

Have the students make physical models of their solutions to the water problems.

Have students present their designs to another class.

Owner: Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder

Contributors: Jay Shah, Malinda Schaefer Zarske, Denise W. Carlson

Copyright: © 2006 by Regents of the University of Colorado

Learning Objectives

After this activity, students should be able to:

• Identify and measure important water quality parameters that engineers use, such as temperature and pH.
• Identify aquatic insects that can be indicators of poor water quality.
• Identify and predict cause and effect relationships in water quality.
• Create a rating tool to measure the water quality of the stream.
• Discuss and defend the results of their investigation through oral and written presentations.
• Understand why engineers are concerned about water quality and its affects on water resources.
• Explain that engineers help maintain water quality for health and recreation through monitoring and treatment.

Materials List

Each group should have:

• 1 copy of each of the three Macroinvertebrate Identification Sheets (or you may print one or two copies for groups to share)

• 1 copy of the Stream Consciousness Worksheet

• 1-liter bottle (of water sample)

• Trays or petri dishes or bowls in which student may observe samples

• 1-2 magnifying glasses or dissecting microscope (if already available)

• Thermometer

• Optional: pH paper or meter (neutral water: pH = 7)

Introduction/Motivation

Why might environmental engineers be concerned with the health of a stream? Would the stream be a possible source of drinking water for the community? Might the stream flow into a community water source? Engineers are interested in the water quality and health of a stream for conservation, restoration and resource use (fishing, recreation and drinking water).

How might an engineer be able to tell if a stream is healthy or not? How can they determine the water quality of a stream or pond? (Possible answers: looking, smelling, testing the chemistry) What are some visible indicators of stream health? (Possible answers: clear water, healthy plant growth surrounding/in the water, macroinvertebrates, presence of fish) What would good water quality look like? (Possible answers: clear or even, crystal clear) What are some indicators of bad water quality? (Possible answers: visible pollution or murkiness).

A macroinvertebrate is an organism without a backbone that can be seen with the human eye (e.g., flies, worms, larvae). Macroinvertebrates are creatures that can be sensitive to pollution. They are good indicators of water quality because they live in or near water most of their lives. They are also fairly easy to collect and observe. Engineers often use macroinvertebrates as indicators of water quality and health.

Procedure

Before the Activity

For this activity, access to a stream, creek or pond is required. There are two options of obtaining samples for this activity: as a class, walk to a stream to collect a sample or have just one adult get the stream sample in advance. (Note: A 1-liter sample of stream, creek, or pond water for each student group should be acquired). The water samples are best if a rock, covered in dirt and debris, or a slimy stick from the stream bottom is included in each.

This activity is written with the assumption that students will walk to a stream, but it can easily be used for already-prepared samples.

Print out (and consider laminating) the three Macroinvertebrate Identification Sheets - Groups 1, 2 and 3 (see Attachments) for students to share to identify their water life.

With the Students

1. Ask the students the following question: “How can we determine if a stream is healthy or not?” Tell them that this is the question they are going to answer today. There are many possible answers, and we are going to explore some methods used by engineers to help us come up with a solution.
2. Divide students into groups of 4. Each group should take a water sample (about a half liter) from the stream in a jar or tub. Try to include at least one rock —covered with dirt and debris — in each sample.
3. Ask students to use the thermometer to determine the temperature of the water sample and record on their Stream Consciousness Worksheet.
4. Then, they should use the pH tester or pH paper to determine the pH of the water and record on their Stream Consciousness Worksheet.
5. Have students record on the activity sheet any other observations or physical characteristics of the water (odor, color, what things are floating or sinking in your sample).
6. Next, ask students to pour a small amount of their water sample onto a petri dish or tray for observation. Using the macroinvertebrate identification chart and a dissecting microscope or magnifying glass, they should identify as many macroinvertebrates in the sample as possible. Have them list on the Stream Consciousness Worksheet which invertebrates and how many of each are found.
7. Student should then take another small amount of their sample and continue counting and identifying macroinvertebrates until they have examined the entire sample. Note: students do not need to count more than 150 invertebrates.
8. Have students count how many of each different kind of macroinvertebrate are found in their sample and write down whether they think their sample indicates good, medium or bad water quality and why.
9. Have the students create their own “rating scale” to determine the biotic index of the water. Example: for “good” invertebrates, assign a value of 10 point to each. For “bad” invertebrates, assign a value of 2 point to each. They should total the points for “good” and “bad” invertebrates and divide by the total number of invertebrates (average bug value). Have them compare this to your (teacher’s) rating scale to determine if the stream is good or bad water quality.
10. Compare your analysis with the class. Did each group come to the same conclusion? Why or why not?
11. Have each group report to the class the number of macroinvertebrates and how they rated the stream. Record the numbers on the board. As a class, calculate an average number of macroinvertebrates found and discuss any discrepancies in rating the stream. Did all the students find that it was very healthy? Or did some students rate the stream poorly while others found it was clean?
12. Ask the students to define why they rated their sample as they did.
13. Review with the students why engineers would care about water quality. Discuss how changes in water quality affect drinking water, or how water quality is used as an indicator of harmful industrial discharges or fertilizer use. Discuss how engineers may be involved in stream maintenance or restoration.

Attachments

Stream Consciousness Worksheet
Invertebrates Identification Sheet - Group 1
Invertebrates Identification Sheet - Group 2
Invertebrates Identification Sheet - Group 3

Safety Issues

Do not allow students to drink their samples.

Troubleshooting Tips

Give students a time limit for this activity or the counting portion of it; otherwise, the students will get caught up in examining the macroinvertebrates.

Assessment

Pre Activity Assessment

Brainstorming: Ask students what they think are indicators of water quality. As a class, have the students engage in open discussion. Remind students that in brainstorming, no idea or suggestion is “silly.” All ideas should be respectfully heard. Take an uncritical position, encourage wild ideas and discourage criticism of ideas. Have them raise their hands to respond. Write their ideas on the board. (Answers may include some of the following: smell, color, murkiness, number of macroinvertiberates, pH, and presence of trash.)

Hypothesize: Have students hypothesize whether or not they think the stream or sample they are going to investigate is healthy. Why or why not?

Activity Embedded Assessment

Worksheet: Have the students record their measurements and observations and follow along with the activity on the Stream Consciousness Worksheet. After students have finished their worksheet, have them compare answers with their peers.

Rate It!: Have the students create their own rating scale to determine the biotic index of the water. They should assign numbers to good and bad water quality macroinvertebrates and develop a way to quantify the health of the stream sample.

Post Activity Assessment

Take a Stand!: Have students write a persuasive essay (teacher should set length depending on time available to spend on writing). In the essay, students should pretend they are environmental engineers that were asked by the community to evaluate a stream. Their essays should clearly explain how they rated the stream and why.

Alternatively, each group of students can create a PowerPoint® presentation and make a presentation to the class. In this case, the class would role play a group of experts from the community, including business leaders, citizens and other engineers.

Owner: Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder

Contributors: Malinda Schaefer Zarske, Janet Yowell, Melissa Straten

Copyright: © 2005 by Regents of the University of Colorado
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0226322. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.

Summary: Students learn a simple technique for quantifying the amount of photosynthesis that occurs in a given period of time, using a common water plant (Elodea). They can use this technique to compare the amounts of photosynthesis that occur under conditions of low and high light levels. Before they begin the experiment, however, students must come up with a well-worded hypothesis to be tested. After running the experiment, students pool their data to get a large sample size, determine the measures of central tendency of the class data, and then graph and interpret the results.
Engineering Connection: Students perform data analysis and reverse engineering to understand how photosynthesis works. Both are important parts of being an engineer.

Materials List

-5 liters (about 1¼ gallons) of aged tap water (tap water in an open container that has been allowed to sit for 36-48 hours to eliminate any chlorine used in municipal water supplies)
-15-20 total of Elodea plants. These are hardy freshwater aquarium plants, sold in bunches at pet stores and suppliers such as Carolina Biological Supply Company (www.carolina.com)
-string, yarn, or twist ties for tying Elodea plants into bunches
-small rocks or similar objects to serve as weights to hold the Elodea plants underwater
-500-ml beakers, enough for one per team
-a few tablespoons of sodium bicarbonate (baking soda)
-timers or watches with second hands, enough for one per team
-small adjustable desk lamps that can be set up so that their light bulbs are a few inches above the beakers and shine vertically down onto them; flashlights with strong beams that are mounted on ring stands will also work. You will need one light source per team.

Introduction/Motivation

Ask your students to each raise one hand high in the air. Then ask them to take a deep breath and hold it for as long as they can. Tell the students to lower their raised hands when they can’t hold their breath any longer. After no one is left holding their breath, ask them why they needed to start breathing again. From their elementary school studies, they should be able to tell you that their bodies need air in order to survive.

Then, ask if they know exactly what is in air. They may not know that air isn’t just oxygen. Explain that most of the atmosphere consists of nitrogen gas (about 78%). Oxygen is the next largest component (about 21%), and a tiny part (1%) is made up of argon (an inert gas), water vapor, and carbon dioxide. If you then ask students what part of the air it is that our bodies need, they should be able to answer that it is oxygen. They probably will also be able to explain that oxygen from the air is picked up in the lungs by the blood and carried to all parts of the body, where it is needed by muscles and the brain and all the other organs and tissues of the body.

Finally, ask students where the oxygen in the atmosphere came from. They may know or be able to reason that it is the result of all the plants that have lived on the earth and have been doing photosynthesis for many millions of years. Then let them know that they can do an experiment to see if the amount of light plants receive can affect this production of oxygen.

Vocabulary/Definitions
Mean:     the sum of all the values in a set of data, divided by the number of values in the data set; also known as the average. For example, in a set of five temperature measurements consisting of 22º C, 25º C, 18º C, 22 º C, and 19º C, the mean temperature is 106º divided by 5, or 21.2º C.
Median:     the middle value in a set of data, obtained by organizing the data values in an ordered list from smallest to largest, and then finding the value that is at the half-way point in the list. For example, in a set of five temperature measurements consisting of 22º C, 25º C, 18º C, 22 º C, and 19º C, the ordered list of temperatures would be 18º C, 19º C, 22º C, 22º C, and 25º C. The middle value is the third value, 22º C. If the data set consists of an even number of values, the median is determined by averaging the two middle values. For example, in a set of six temperature measurements consisting of 20º C, 22º C, 25º C, 18º C, 24 º C, and 19º C, the middle values are 20º C and 22º C. Therefore, the median value is the average of 20º C and 22º C, which is 21º C.
Mode :     the value in a set of data that occurs most frequently. For example, in a set of five temperature measurements consisting of 22º C, 25º C, 18º C, 22 º C, and 19º C, the measurement of 22 º C occurs most frequently, so it is the mode. It is possible to have two or more modes in a set of data, if two or more values occur with equal frequency.

Procedure

1. In a class discussion format, students will establish a hypothesis to be tested by the class in the experiment.
2. Working in teams, students will set up and conduct the experiment. Each team will conduct two trials: one with the plants lit only by the ambient light available in the classroom when some or all of the room lights are turned off, and one with the plants receiving bright light from the desk lamps. The data collected will be the number of bubbles of oxygen that are given off by the plants in a five-minute period, first at low light levels, and then at high light levels.
3. The teams will come together and pool their data from each of the two trials. From these data, students will individually determine the mean, median, and modes for the numbers of bubbles produced during the two different light conditions.
4. Students will then individually graph the data, using bar graphs that show the mean numbers of bubbles and the ranges for each test condition.

Part 1: Generating a hypothesis

Explain to the class that before a scientist starts an experiment, he or she must first have a prediction about what the outcome of the experiment will be. This prediction is known as a hypothesis. A hypothesis is not simply a guess, however. Instead it is a prediction based on prior knowledge of or experience with the subject. For example, if a gardener wanted to find out if it was really necessary to fertilize his zucchini plants, he or she might grow twelve zucchini plants, but fertilize only half of them. In this case, the hypothesis being tested might be, “Fertilized zucchini plants will produce more zucchinis than unfertilized zucchini plants.” The data collected to support or refute the hypothesis would be the total number of zucchinis produced by the fertilized plants, compared to the total number produced by the unfertilized plants.

Point out to students that in the zucchini experiment, the gardener collected data that involved numbers. In science this is usually the case, because numbers can easily be compared and they are based on things that actually happened, as opposed to things that the experimenter thought happened.

Then, explain briefly how the photosynthesis experiment will be set up, and ask the class w