1. Students will realize that there are many forms of energy and they will be able to name the various forms of energy.
2. Students will be able to develop energy conversion diagrams depicting the energy conversions involved in the operation of common devices and/or organisms.
3. Students will be able to provide a general explanation of how heat is conducted in a Ben Franklin stove.
4. Students will be able to explain how a battery converts chemical energy to electrical energy and what happens to batteries when they go "dead".
The science portion of this unit revolves around four investigations which students will conduct in the science classroom. Each activity is designed to familiarize students with the major forms in which energy can be classified: light, sound, chemical, electrical, magnetic, mechanical, heat and elastic energy. As students progress through each activity, they will gain firsthand knowledge of the many possibilities for converting one form of energy into another. The first activity is designed to familiarize students with the fact that energy comes in many different forms and it is possible to convert one energy form into one or more other forms of energy. Students are presented with a variety of energy conversion devices at a number of stations around the classroom. After examining the devices at each station, they are asked to determine the types of energy conversions involved. This activity is designed to provide students with a basis for recognizing the different forms of energy, while gaining an appreciation for the energy conversion process.
In the second activity, students construct energy conversion diagrams for devices with which they are familiar. By using printed sets of cards and arrows, students construct energy conversion diagrams. Physically arranging the cards provides students with a way to help organize energy conversions and aids them in better organizing these concepts in their minds.
Students gain firsthand experience in converting chemical energy to light and heat energy in the third activity. Presented with an advertisement, written by Benjamin Franklin himself, for the Ben Franklin fireplace, students will compare how well the Franklin fireplace heats compared to a conventional fireplace. Students will look at the energy conversions involved in heating by fire.
In the final science activity, students directly observe that chemical changes can produce electricity. Looking at a dissected dry cell, students will be able to determine that the chemicals in the dry cells must be responsible for producing the electrical current. They will then experiment with reviving "dead" batteries.
Begin the unit by showing the video "Kid Conversions". Ask students to pay particular attention to the different forms of energy and the energy conversions shown in the film. After viewing the video, break students into cooperative groups. Ask each group to come up with as many ideas as they can for how to move the truck the required 10 meters. The ideas should be different from those shown in the video. Remind students that they need to identify the energy conversions involved in all of their ideas, just like the kids in the video did. Encourage creativity! If time permits, you may want to actually try some of the students' ideas in the hallway.
Prepare a bulletin board illustrating the eight forms of energy; light, heat, sound, electrical, magnetic, elastic, mechanical and chemical. This should be referred to repeatedly during class discussions as students progress through the unit. You may want to ask students to bring in magazine pictures depicting each form of energy or various energy conversions. These could be added to the bulletin board.
Keep close tabs on the progress of students' written work. Many times, students will get so involved and excited with using the materials and equipment that they will not follow through by completing the written portion of each activity. Each activity has a Summing Up section in which students are asked to write answers to a number of questions. These questions are vital to the process of truly understanding the concepts involved. Insist that students complete these questions before progressing to another activity.
While students are experimenting and collecting data in groups, it is recommended that each student complete their own student data sheets as well as answering the Summing Up questions. A personal response rather than group responses to the Summing Up questions will help to assure student involvement in each activity.
You may wish to devise a final evaluation for the science portion of this module. Here are two suggestions for evaluation:
Authentic Assessment: Ask students to identify each of the energy forms present in the story below. Challenge students to prepare energy conversion
diagrams for those instances in which energy is being converted from one form to another.
The Unfortunate Weekend:
After much arm-twisting, Alex and Andrew have finally been given permission by their parents to go on a weekend camping trip. They load up their gear and
head out of town on foot. After walking for nearly two hours, they finally reach their destination; a secluded spot in a small wooded area in the country. After a quick rest they set up their camp, consisting of a small tent and a pile of firewood. Unfortunately their matches have gotten a bit wet and they are
unable to get a campfire started. That's OK...They are hungry enough to eat cold hot dogs. Darkness is soon upon them and they begin feeling a bit isolated without the warm comfort of a campfire. They decide to use their flashlight to brighten up the tent and have a quick card game. But after only 10 minutes of
use, the light becomes dimmer and finally goes out. What bad luck. They forgot the extra batteries! Things go from bad to worse as the sound of distant thunder rolls toward them. Soon the sky is lit with bright flashes of lightening and the ground seems to shake with the thunder. Not a good night to be out. Andrew wishes he were back home, but Alex insists they are having a
good time. As the rain continues to pour down, water begins dripping through the roof of the tent. Alex sees this as a bad sign. The lightning is so intense that it seems to be steady. "Wait a minute", says Andrew, "that is a steady light". "Someone is coming, where can we hide?" But before an escape
can be planned, the tent unzips and in steps Dad. Alex feels a rush of relief. Although he would never admit it, he was very happy to be "rescued" on a night like this!
Conversions Galore! We have been studying eight forms in which energy is typically found; light, heat, electrical, chemical, sound, elastic, magnetic, and mechanical energy. Your challenge is to think of one example of as many different energy conversions as you can. For example, can you think of one device that converts light energy into heat? What about one for converting light into electricity or light into sound or light into mechanical energy? Yes these conversions can really happen! Present your list of conversions in the form of energy conversion diagrams. Be sure to write the name of the device/object above the arrow in your diagrams.
Teacher Notes
Objectives:
Students will realize that there are many forms of energy and these forms include chemical, electrical, mechanical, heat, magnetic, sound, light and elastic energy.
Safety Warnings:
None
Suggested Teaching Strategies:
A worksheet explaining the activity follows. This can be distributed to students. If your students will be doing this activity together, you might want to save paper by giving verbal directions to the activity. Whichever path you
follow, some suggestions are provided below for introducing the activity.
Begin the activity by asking students to identify as many different forms of energy as they can. In compiling a class list, explain that there is some disagreement as to exactly what these major categories of energy should be. Many students will give good ideas, listing forms of energy such as nuclear or solar. These energy forms are considered as a subset of chemical energy. Lead students to arriving at the eight forms of energy listed in the objectives.
Allow students sufficient time at each station to make observations, then answer each of the Summing Up questions posed. Remind students not to move to another station until they have completed the Summing Up questions.
This activity is designed to be exploratory in nature. Students should be given an opportunity to explore the different forms of energy. Do not expect students to be experts at identifying forms of energy at this stage of the unit. Rather, use this activity as a starting place for discussion. Students will likely be confused by batteries as a form of chemical energy. In addition, they may not note all of those instances in which heat is also given off as a by-product of the conversion process. For example, an electric pencil sharpener will feel warm after use, but the main energy conversion is electrical to mechanical, with some energy being wasted as heat. Some students may notice this, while others may not. Encourage discussion among students within groups. Ask students to try to make a group decision in answering the Summing Up questions before moving on to the next station.
Please note that some of the sample answers to Summing Up may differ in those instances in which you use items other than those suggested in the materials list.
Materials:
cards for each station (see Appendix A)
The specific materials needed for each station are listed by station number below, along with tips for securing some of the items. If you are unable to secure the items suggested, either substitute other items, or eliminate that station.
Materials:
radiometer, hairdryer, flashlight or lamp, paper fan
Sample Answers for Summing Up:
1. Students will try to rotate the radiometer using the light, heat from the hair dryer, and moving air from the fan. They will discover that light from the flashlight does the best job of rotating the radiometer fins. Heat from the
hair dryer will cause the fins to rotate for a few seconds. As the entire inside of the radiometer tube becomes heated, the fins will come to a stop. Moving air from the paper fanning has no affect on the radiometer fins.
2. Light energy was needed to rotate the radiometer.
3. Light energy was converted to mechanical energy as the fins moved.
Materials:
battery powered tape recorder, battery powered radio, battery powered toys that make sounds
Sample Answers for Summing Up:
1. Each of the objects tested are powered with batteries. This is a form of chemical energy.
2. Sound energy was produced in each of the devices. Some of the devices produced heat as well.
Materials:
rubber bands of various thicknesses & balloons
Students can observe the stretched balloons & rubber bands heat up.
Sample Answers for Summing Up:
1. Mechanical energy was needed to stretch each of the rubber bands.
2. Elastic energy caused the rubber bands to come back to their original size.
3. Heat energy was produced by the rubber band as it was stretched and unstretched.
Materials:
A variety of toys which can be wound up and then move by jumping or spinning.
Sample Answers for Summing Up:
1. Each toy needed to be wound up to move. This means that mechanical energy was added to each toy, since your hand moved the wind-up part of each toy.
2. Each of the working toys has mechanical energy, as evidenced by their motion. Sound and heat were also given off by the toys.
Materials:
magnet, a variety of objects, some of which will be attracted to the magnet and some that will not.
Sample Answers for Summing Up:
1. Magnetic energy was used to attract the objects to the magnet.
2. When the objects were not attracted by the magnet, there was no energy conversion involved.
3.Magnetic energy was converted into mechanical energy as the objects moved toward the magnet.
Materials:
party noisemakers, bells, any wind or percussion musical instruments
Sample Answers for Summing Up:
1. Each instrument worked by either blowing on it or by hitting it. Both of these involve mechanical energy.
2. Each of the working objects have sound energy.
Materials:
food items such as fruits and nuts
Sample Answers to Summing Up:
1. If you choose nuts and fruits, it may be easier for students to visualize that these products require the sun's energy, or light, in order to grow. If
processed foods are used, students may list some of the forms of energy required during the processing phase, such as electricity.
2. Food stores energy in the form of chemical energy.
3. Once eaten, the chemical energy stored in the food is converted into heat and mechanical energy (muscle movement). Many students will not realize that heat
energy is formed also. Let this be a point of discussion following the activity.
Materials:
Materials could include any devices that need to be plugged in to operate. Each device should produce motion and/or heat. Good examples would be a hair dryer,
an electric fan, an electric pencil sharpener, an electric mixer (do not include the beaters!), and a heating pad.
Sample Answers to Summing Up:
1. Each device needed electrical energy to make it operate.
2. Each of the working devices produced mechanical energy (motion) and/or heat energy.
Materials:
plastic spoons, rabbit fur or fuzzy stuffed animals, styrofoam peanuts
Certain types of styrofoam work better than others. Experiment with different types prior to class and make those available that work the best. This activity has the best results when the humidity is low (winter).
The fur causes a build-up of negative charges. The styrofoam appears to levitate because negative charges on the styrofoam repel the negative charges on the plastic spoon.
Summing Up
1. Electrical energy was used to suspend each object. Some students may call this static electricity. This is acceptable, although this is not one of the energy forms listed in on the student page of this activity.
2. The electrical charges caused each of the charged objects to move, converting the electrical energy into mechanical energy.
Suggested Discussion Questions:
Once students have completed all of the stations, you may want to ask students some or all of the questions posed below.
Go through each station by discussing the energy conversions that took place for each device. Get the class to reach a group consensus on the conversions. Using an overhead, diagram the changes involved. For example, in Station #2, Quiet Please, electrical energy was converted into sound energy. This could be represented on the overhead in diagram form as follows:
Ask students if anyone noticed any other forms of energy at this station. Have the radio operating for some time prior to class and ask one of the students to feel the radio. They should notice that the radio is warm. This means that heat energy was also formed in this conversion. Revise the energy diagram to reflect the formation of heat in the conversion.
Ask students in which other instances they observed heat being given off as a by-product. Point out to students that during any useful transformation of energy from one form to another, heat is also given off.
After students have completed the Summing Up questions, hold a class discussion in which students share their ideas with the class. It is likely that students will give a wide variety of answers to the Summing Up question related to the source of the human body's mechanical energy. Write all student suggestions on the board. While some students will name "food" as being the source of our energy, food is really a form of chemical energy. Others may list the sun or light as the source of our energy. Since the sun is the source of energy for the food chain, this is also a true statement. Remind students that their bodies are like a machine that converts the chemical energy contained in food into the muscular energy necessary to move objects. Trace the steps back for students so they can see how energy is transformed along the way.
Students need to practice thinking of examples of energy being converted from one form to another. Appendix A contains energy diagrams which may be used as overheads to help explain the energy conversions for various stations.
Ask students if there were any stations in which more than one energy conversion took place. Any station in which batteries were used had more than one energy conversion involved. Chemical energy was converted to electrical energy with batteries. This electrical energy was then used in a number of devices to produce sound, motion, and/or heat.
Background:
Energy can be changed from one form into other forms. This is called energy conversion. People have invented ingenious ways of converting one form of
energy into other useful forms. Throwing a rock transforms chemical energy in
your body into mechanical energy. Starting a fire is a way of converting chemical energy into light and heat. A steam engine is a more complex machine. It converts heat energy into motion. In an electric generator, motion is
converted into electrical energy. In all energy conversions, the useful energy
output is always less than the energy input, with some energy being wasted as heat.
What are some of the different forms of energy? First there is energy from the sun: light and heat. Next, there is mechanical energy, the energy motion. Mechanical energy turns the wheels of a car, for example. Chemical energy is released when different chemicals react or change their form. Electrical energy is the flow of electrons through a wire.
The human body is like a machine designed to convert the chemical energy contained in food into mechanical energy evidenced by movement of our limbs. Food gives up its chemical energy to produce heat energy (body temperature) and mechanical energy (muscle power). Batteries turn chemical energy directly into electrical energy. Chemical energy in wood turns into heat and light energy when it is burned. The flame you see in a fire is the light energy given off as the energy is converted.
These are examples of simple conversions. One of the many ways we can make electrical energy is through one-step conversions, such as mechanical to electrical. For this, you need a machine called a generator. You can use your mechanical energy (muscle power) to turn the crank connected to an electrical generator to make electricity. A windmill captures the mechanical energy of wind to turn a generator. Falling water can turn a waterwheel which is connected to a generator.
There are many energy conversions that take more than one step. In a car, for example, chemical energy in gasoline is converted to heat energy by burning the fuel and then to mechanical energy. The heat creates a force that pushes the pistons (this is mechanical energy). Gears transfer this mechanical energy into movement of the wheels.
Suggested Evaluation Strategy:
Ask students to locate at least 5 devices or objects at home that convert energy. List the forms of energy needed to operate each item and the form or
forms of energy into which it is converted. Remind students to note the type of device or object involved.
Student Pages
Most of us don't realize just how important energy is in our lives. Every facet of our life involves energy. One of the reasons we tend to take energy for granted, is that we may not always recognize energy when we see it. For example, did you know that sound is a form of energy? So is a stretched rubber band!
People tend to group energy into a number of different categories. While not everyone agrees on what these categories should be, for this unit we are going to use the eight categories of energy forms shown below.
Energy is constantly changing from one form to another. When this happens it is called an energy conversion. You can be thankful that there are so many different ways to convert energy from one form to another. If this were not possible, you would not be able to enjoy your tape player or television set, or would not even be able to get your roller blades to work.
In this activity, you will be gaining experience with energy conversions. There are a number of stations set up around the classroom. Your job is to progress through each of these stations. At each station you will find a card with written directions for the investigation. Read the directions on each card carefully, performing the tasks as directed. It will not be necessary for you to record data gathered for each of your investigations. However, you must answer the Summing Up questions listed for each station. Complete the Summing Up questions at each station before moving to another station. You may progress through the stations in any order you wish. It is not necessary to begin with Station #1. Please make certain that your Summing Up answers are clearly labeled with the correct station number. Good luck!
Summary of Procedures
Teacher Notes
Objectives:
Students will be able to develop energy conversion diagrams depicting the energy conversions involved in the operation of common devices and/or organisms.
Materials:
Make multiple copies of the cards contained in Appendix A. Place one set of cards and at least six arrows into envelopes. Prepare enough sets to allow each student group to have their own set of cards. It would be a good idea to place
several copies of the mechanical, electrical, and chemical energy cards into each envelope, as students are likely to devise situations in which many conversions are made.
Suggested Teaching Strategies:
The student sheets are designed to be handed out to students. However, students do not need to write on these sheets. You may choose to present the directions
to this activity orally rather than distributing sheets to each student in your classroom. Another alternative is to give each cooperative group one activity sheet. Either way would save paper and the cost to print it and would not
diminish the quality of the activity.
This activity should not require much in the way of introductory remarks since students have just completed the first activity. Allow students sufficient time to get creative with their arrangements in the energy conversion process.
Sample Answers to Summing Up:
1. Student responses will vary. Make certain that students are including the names of the object above the arrow in each of their diagrams. Remind students
that in many devices, heat is given off as an unwanted by-product.
2. Students are likely to mention that light, heat, and sound energy are produced by devices such as televisions and computers. In both of these, heat is a by-product and considered wasted energy in the conversion process.
3. Student answers to this question may vary. They may suggest the human body using food as its energy source. The conversions involved would depend on the food source ingested, but would begin with the sun. Make certain that student answers make sense in terms of the energy conversions involved.
4. Student answers will vary. Encourage creativity, allowing ample time for student groups to work on this question. Make certain that students prepare a drawing and an energy conversion diagram of their invention.
Extension Ideas:
Challenge students to invent a device which involves all eight of the forms of
energy on your cards. The device should perform some useful task. It is likely that your energy conversion diagram will involve many steps. (Look back at the diagram of a moving car to remind yourself how to diagram multi-step
conversions.) Prepare a drawing of your invention. Label each part and what it does. Make an energy conversion diagram showing all of the energy conversions involved.
Student Pages
In the last activity you observed energy being converted from one form to another. From that activity you learned that energy comes in many forms and can be changed into many forms. In many of the conversions, heat is also formed as a by-product.
In this activity, you will once again be studying energy conversions. Instead of observing devices that convert one form of energy into another, you will be thinking of examples of devices that do the converting. For example, there are lots of different devices that convert electrical energy into sound energy. A doorbell is one of these. This can be illustrated with an energy conversion diagram. The diagram for this conversion is shown below. Notice how the device used to make the energy conversion is listed above the arrow.
In this activity, you will be using cards and arrows to make your own energy conversion diagrams. Using your cards, the above diagram for the door bell would look like this:
Most energy conversions are not this simple. The energy conversion diagram below shows a more complicated process; the energy conversions involved in operating a car. In a car the chemical energy in gasoline is eventually converted to mechanical energy in a moving car.
Materials:
envelope containing energy forms symbols and arrows
Let's Investigate:
In this activity, your job will be to construct energy diagrams for a number of situations described in the Summing Up questions. The cards and arrows will
help you to arrange your thoughts. Use a separate sheet of paper to record each drawing.
Summing Up:
1. Make energy conversion diagrams for five different devices in your home. Write the name of the device above each arrow. Don't forget to include heat energy for those devices that heat up when they are used.
2. Name one device that converts electricity into light, heat and sound. Make an energy conversion diagram for this device. Don't forget to write the name of the device above the arrow.
3. Think of an object/device that must make a large number of different energy conversions to operate. Make the longest energy conversion diagram you can think of for this object, that makes sense. Don't forget to write the name of the devices/objects involved in each conversion above each arrow.
Teacher Notes
Objectives:
Students will be able to provide a general explanation of how heat is conducted in a Ben Franklin fireplace. This will include explaining how heat is conducted from a metal fireplace.
Materials:
Band-Aid box or SPAM can
clock with a second hand
hot mits
empty pop cans
thermometers
safety goggles
matches
cups for used matches
birthday candles (1/2 inch base)
cardboard lids lined with aluminum foil
glass or plastic aquarium or 5 gallon ice cream bucket
Glass aquariums work best for this activity. However, if you do not have enough, try using plastic aquariums. Set the candle and Band-Aid box on thick pieces of cardboard in the bottom of the aquarium to prevent the heat from melting a hole in the aquarium. Ice cream buckets also work well.
Band-Aid boxes work best for this activity. Kids may be able to supply their own from home. Be sure to keep them for next year. Large SPAM cans also work well. You will need to cut a hole in the front of each metal box (see drawing on the student page). This would be best done by the teacher prior to class. If the holes are punched and folded inward, sharp edges will be eliminated. Soup cans will also work for this experiment. Remove the lids and use the cans with the open side facing down.
The Chimney is best made from a small juice can, as these are not very flammable and are about the right size. If this is too much of a hassle for you, the experiment works just as well with a hole cut in the top, but no juice can inserted. Another option is to cut the top and bottom from an aluminum pop can. Fold over all four edges to eliminate sharp edges. Roll the metal piece into a small chimney. This chimney can be stuck through a hole in the top of the Band-aid box and up through the lid over the aquarium.
Helpful Hints: In order to trap the heat in the aquarium (and thus simulate a closed room), a cover is needed for the aquarium. Cardboard will work well, but presents a slight fire hazard. The cardboard should be covered with aluminum foil. Be certain to extend the aluminum foil lining up through the chimney, as this area will get hot enough to catch the cardboard on fire. Students must make certain that they use the same type of cover for both segments of the activity, as this will affect the temperature change. Students will get the best results if they take a temperature reading every minute. Ask students to take readings for five minutes.
Safety Warnings:
Students will be using a lighted candle for this experiment. This means that they should be required to wear safety goggles while the candle is lit.
Remind students that the Band-Aid box will be heated by the candle. It will get hot enough to cause a burn. Remind students to allow the metal boxes to cool
for several minutes before attempting to move them. Hot mits available for students to use.
Suggested Teaching Strategies:
This activity will run most smoothly if the teacher prepares the fireplaces and chimneys prior to class. These may be saved and reused each year.
Print enough copies of the Ben Franklin advertisement (see Appendix A) to give to each cooperative group. Introduce the reading by asking students who Ben Franklin was and what he did. Ask students to pay special attention to all of the benefits which the stove is advertised to have. Portions of the advertisement will be difficult for students to read, as it is written in the language and style of Franklin's time. One way to help simplify the reading is to assign each student group one of the 14 points listed as advantages of the Franklin fireplace. Challenge students to translate each of the 14 points into easily understood language. The revised points should then be presented by each group to the class to help everyone better understand Franklin's arguments.
You may want to ask the social studies teacher to come to your class, or discuss in his/her class, the fuel wood shortage taking place in Franklin's time. This additional information should help students to see the real necessity of using the Franklin stove, since it was advertised as emitting more heat while using less wood. Once students have a better understanding of Franklin's advertisement, you may proceed with the activity. Students will be conducting an experiment to test a model of the Franklin fireplace to see if it really helps to better heat a room.
If you do not have enough glass aquariums, one for each student group, set up the experiment as a demonstration.
Background:
As the number of European settlers in North America began to grow, the fuel supply (wood) was used at a faster and faster pace. Those forests closest to cities were cleared first. Eventually loggers had to go farther away from the
cities to supply wood to the townspeople. This drove up the price of wood. Ben Franklin recognized the importance of this situation. He decided that wood could be saved by designing a special stove that would burn wood more efficiently. Regular fireplaces burned wood very inefficiently. Most of the
heat went right up the chimney, causing drafts and uneven heating throughout the room. The drawings included on the student page help to illustrate the differences between the Franklin fireplace and more traditional fireplaces on the time.
To help solve this problem, Ben Franklin designed a special fireplace. Appendix A contains a copy of Franklin's advertisement for the stove. This ad was written by Benjamin Franklin himself. Students will find some of his phrases a bit strange, although they accurately reflect the language used during that period of history. The advertisement describes the special features of his new woodburning stove.
Sample Answers to Summing Up:
1. The Franklin fireplace should heat the "room" to between 4 and 8 degrees C warmer than the "room" with the conventional fireplace. Once the candles are
extinguished, the "room" with the Franklin fireplace will stay warm longer than will the room with the candle only.
2. Chemical energy --- Light energy + Heat energy
3. The heat from the candle flame strikes and heats the metal box. This warms the air in contact with the box. This occurs on all sides of the box. Thus, the metal box becomes surrounded with warm air. This creates a current by which the warm air moves up and away from the "fireplace" (Band-aid box), and is replaced by cooler air, which in turn warms up.
Student Pages
Benjamin Franklin's advertisement might have been difficult for you to read, but there should have been no doubt that his invention sure sounds good. Did you think his arguments made sense? Well, this experiment will allow you to collect some data comparing the conventional fireplace design with the Franklin fireplace. While we will not be working with real fireplaces, we can test a model of each. You will be trying to discover if there is a difference in temperature between a room heated with a conventional fireplace and one heated with a Franklin fireplace?
Materials:
chimney
Band-aid box or metal can
aquarium
candle and matches
thermometers
safety goggles
hot mit
SAFETY WARNING
You will be using a lighted candle for this experiment. Be sure to wear safety goggles while the candle is lit. The Band-aid box will get very hot. Allow the metal Band-aid box several minutes to cool before attempting to touch it. If
you get burned, let your teacher know right away.
Let's Investigate:
Before beginning, study the picture of each model shown on the next page.
Conventional Fireplace:
Set up the aquarium to look like conventional fireplace model shown in the first drawing. Record the temperature reading on the thermometer in the aquarium
before lighting the candle. It might be a good idea to measure the starting height of the candle as well. You will want to make certain that you use a candle of the same height when testing the Franklin fireplace. Once you have recorded the starting temperature, light the candle. Make sure that the candle
is directly under the chimney. Read and record the temperature every 30 seconds for 5 minutes. After 5 minutes, blow out the candle. Keep reading and recording the temperature for another 5 minutes.
Franklin Stove:
Remove the lid from the aquarium, allowing the inside to cool down for several minutes. Make certain that the sides of the aquarium have cooled down too
before beginning to collect data. Record the starting temperature. Place the candle into the Franklin stove model (the band-aid box) and light it. Read and record the temperature every 30 seconds for 5 minutes. After 5 minutes, blow
out the candle. Keep reading and recording the temperature every 30 seconds for another 5 minutes.
Summing Up:
1. Prepare a graph showing the temperature changes in both aquariums throughout the experiment. Be sure to include the heating and cooling temperatures.
2. Write a sentence summarizing the data on your graph.
3. Draw an energy conversion diagram showing the energy conversions involved in the Franklin fireplace.
4. Which of Franklin's 14 advantages are supported by your findings? Explain your answer.
Challenges:
Teacher Notes
Objectives:
Students will be able to outline the chemical changes involved in energy production in a dry cell.
Materials:
dead dry cells
eye droppers
light bulbs ( 2.2 volts or less)
distilled water
insulated copper wire
The dry cells should be size AA or D. Do not use alkaline or rechargeable batteries as the chemicals inside these may be harmful. Read the label and if you see "Alkaline" or "Rechargeable" on the label do not use them. Dry cells with a cardboard jacket or case work best (Eveready brand). If only those with metal jackets are available, they can be used, although it may require a wire cutters and pliers to remove the outer covering.
Use the same insulated copper wire students used to make their own light bulbs. Cut pieces that are approximately 10 cm long. Each student group will need one 10 cm length of wire.
To prepare the dry cells for student use, it is best if the teacher punches the holes in the dry cells before class. You could allow students to do this, but there are safety problems with students handling the hammering. Using a nail, hammer two holes in the top of each dry cell. You may need to have someone hold the batteries while you pound.
Safety Warnings:
Do not use alkaline or rechargeable batteries, as these contain chemicals that may be caustic to students.
Suggested Teaching Strategies:
It is difficult for students to picture a chemical reaction occurring within a dry cell. Most students have a preconceived notion that when a chemical change occurs it involves bubbling, flames and gases. This is simply not always the
case. By cutting open the dry cell, students can at least see that the central rod is made of one material and the black paste of another. It is important for students to see that the dry cell will not light the bulb at first. Only after
water is added will the bulb light. This offers proof that something must be going on inside the dry cell.
Dissect a dry cell and have it available for students to see. This can be done safely as follows:
After students have completed their Summing Up questions, hold a class discussion so students can share the ideas they wrote for answers.
Background:
A battery is a device designed to produce electricity by converting chemical
energy into electrical energy. A battery is made of several smaller units, called electrical cells. Each cell consists of two electrodes made of different materials surrounded by chemicals. These chemicals are called electrolytes and are composed of a mixture of chemicals that produce an electrical charge.
Electric cells can be either wet or dry cells. A car battery is an example of a wet cell. It is called a wet cell because the electrolytes in it are liquids. Flashlight "batteries" are examples of dry cells. In a dry cell, the electrolyte is a pastelike substance.
Many people refer to dry cells as "batteries". Technically, this is incorrect. A battery is a series of dry cells, not just one.
As shown in the diagram, the dry cell shown has one electrode made of carbon and the other made of zinc. The part of the dry cell that sticks up is called the terminal. The chemicals in the paste react with the carbon electrode, pulling off electrons. At the same time, the paste chemicals react with the zinc lining causing electrons to build up on the zinc. Thus, the zinc electrode becomes negatively charged, while the carbon electrode becomes positively charged. Because there are opposite charges between the electrodes, charge will flow between the terminals if they are connected by a wire.
Sample Data:
Students should discover that the brightness of the bulb increases as more water is added to the dry cell. Allowing the dry cell to sit overnight will give time for the water to seep through the entire "powder" area. The bulb should appear
the brightest after the wetted dry cell is allowed to sit overnight.
Summing Up:
1. Students may represent the energy conversion diagram as shown in either of the situations below, both of which should be considered acceptable:
Chemical Energy ----} Light Energy
Chemical Energy ----} Electrical Energy ----} Light Energy
2. From experiences with this activity, students should realize they needed only to add water to the dry cells to get them to work again. This should lead students to conclude that the chemicals within the dry cells are not really used up; the water has simply dried up.
3. Students should devise ways of getting water into the used dry cells without cutting off the outer covering. Some suggestions that really work include drilling holes in the top of the dry cell and soaking it in a cup of water overnight or drilling holes in the sides of the dry cell and again soaking it in a cup of water.
Extension Idea:
Challenge students to research the history of batteries. Ask them to discover what role a "twitching frog leg" played in the development of the first battery,
called a voltaic pile. Students may be able to discover enough information to
build their own battery. Small disks of cardboard can be soaked in a solution of salt water or vinegar. By separating pieces of zinc and copper, an electric charge can be generated. Students should be able to pile pennies, soaked
cardboard and dimes to create their own battery. Students should be able to locate a picture of the first voltaic piles in a book about electricity.
Ideas for this activity were developed by D. Louis Finsand, Price Laboratory School, University of Northern Iowa.
Student Pages
One of the most difficult energy conversions to visualize are those in which a chemical change is involved. It seems strange that just by adding the right substances together, electricity or heat can be produced. One of the most common examples of energy conversions involving chemical energy, is dry cells and batteries. Everyone has experienced the frustration of trying to enjoy some nice music on a portable radio only to find that their batteries are "dead". Well, in this activity, you will be able to see how to bring a "dead battery" back to life!
Materials:
dead dry cell (battery)
flashlight bulb
distilled water
eye dropper
insulated wire with ends stripped
Let's Investigate:
Test the battery by making a complete circuit with the light bulb and wire. Simply hold one of the stripped ends of the wire against the bottom of the battery. Hold the other end against the metal bulb base. Press the bulb firmly on top of the battery. It may help to rub the bulb base against the battery top
to make certain contact is made. If your bulb glows, then your battery is not dead. Give it back to your teacher if that happens and ask for a real dead one!
Your teacher has punched holes in the top of the dry cell. Place a few ml of distilled water into a cup. Using an eye dropper, add 5 drops of water to the holes in the top of the dry cell. Test to see if the dry cell now lights the bulb. Keep adding water to the holes, 5 drops at a time. After each 5 drops, test the dry cell to see if the bulb lights. Record your data in a table. If the water begins to overflow, give the water a few minutes to soak in.
Let the wet dry cell sit overnight. Test the dry cell again the next day, recording your data in the data table.
Summing Up:
1. Write an energy conversion diagram showing the energy conversions that occur in lighting the bulb.
2. Do you think that the chemicals inside the batteries are actually all "used up" in a dead battery? Explain your answer.
3. There are certainly a large number of dry cells that are discarded by people each year. Knowing what you now know about "dead batteries", propose a design for reviving old batteries. Try to keep it simple enough to allow the dry cells to remain useful in the many devices in which they are now used (tape recorders, radios, flashlights, etc.). Include a drawing and explain your process in detail.
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