# Teacher Activities

A partial listing of the teacher activities is contained here.

 Blowing Up a Balloon With Heat Investigating Popcorn Telling Hot from Cold Flying Napkin Cooling or Warming Breezes Summer and Winter Colors Bouncy, Bouncy, Oh My Rubber Ball! Heat Absorption by Can Surface Expansion Joints. Why do We Need Them? Cold Gas

### 1-2) Blowing Up a Balloon With Heat.

Material: small balloon, test tube, water, hot plate, 2-600ml beakers.
1. Stretch the opening of the balloon over the test tube so it is tight.
2. Fill the two beakers of water, placing one of them on the hot plate which should be on medium high setting.
3. Place the test tube in the beaker on the hot plate. As the water heats up observe what happens to the balloon. Place in cold water beaker and observe what happens

QUESTIONS/CONCLUSIONS

1. Describe what happens to the balloon in the two cases.
2. Why does the balloon expand?
3. What happens to the balloon when the heat source is removed? Why?
4. Why do tire manufacturers advise checking tire pressure when the tires are cold?

### 2-1) Telling Hot from Cold

Material: bowls of hot water, cold water, room temperature water. Use 600 ml beakers for the bowls.
1. Obtain three bowls large enough to place a hand inside. Fill one with hot water (not hot enough to burn), another with cold water, another with lukewarm water.
2. Place the hot water on your left, cold water on your right, and lukewarm water in the middle. Now place your left hand in the hot water and your right hand in the cold water. Leave them there for two minutes.
3. Pull your hands out and shake off the water. Now place them both in the lukewarm water. Observe what happens.

QUESTIONS/CONCLUSIONS

1. Did you predict what would happen when you placed both hands in the lukewarm water?
2. Describe your sensation when you placed both hands in the lukewarm water.
3. Explain your sensation when both hands were placed in the lukewarm water.

### 2-2) Cooling or Warming Breezes?

Material: two thermometers, small electric fan (brought from home).
1. Take two identical thermometers and check that their temperatures indicate the same. Place one thermometer in front of an electric fan and the other thermometer near, but not in the path of the air blowing through the fan.
2. Make and write down your prediction as to which thermometer will be the coolest.
3. Let the fan blow for five minutes and read the temperature of each thermometer.

QUESTIONS/CONCLUSIONS

1. What is your prediction for the coolest thermometer? Give your reasons.
2. What was your experimental result? Does it make sense?
3. Why did the thermometers read the same?
4. Explain why we use electric fans to cool us in hot weather?
5. Predict what would happen in this experiment if the thermometer bulbs were wet?

### 2-3) Bouncy, Bouncy, Oh My Rubber Ball!

Material: rubber ball (like a tennis ball), meter stick, refrigerator freezer (or ice chest and sealable plastic bag).
1. Find a hard even floor and measure a distance two meters high. Mark the spot.
2. With the ball at room temperature drop the ball from the 2 meter height and note how far back up it bounces. Do the measurement several times and take the average. Mark this spot.
3. Put the ball in the freezer for 30 minutes. If you don't have a freezer place the ball inside a sealable plastic bag and stick it in the ice chest. Do other activities while you wait for the ball to get cold.
4. Make a prediction as to whether the cold ball will bounce higher, lower, or the same.
5. Repeat step 2) with the cold ball and mark the new height.

QUESTIONS/CONCLUSIONS

1. Why do we take several measurements to determine the height the ball bounces? Do the various measurements vary?
2. What prediction did you make as to what the cold ball would do? Explain your prediction.
3. Explain why the cold ball bounced lower.

### 2-4) Expansion Joints. Why Do We Need Them?

Material: Tin or aluminum soda can, hammer, nail, pliers, candle, matches.
1. Use the hammer to drive a nail into the top of the can. Use the pliers to ease the nail out gently. Put the nail in the hole again. Make sure the nail has a tight, not loose, fit in the can.
2. Take the nail out again gently and heat the nail using a candle (or other flame source).
3. Try to put the hot nail into the hole.

QUESTIONS/CONCLUSIONS

1. What difference did you find when you tried to put the hot nail into the can.
2. What caused the difference with the hot nail?
3. Explain why bridges have expansion joints and sidewalks have spaces between their sections.

### 3-1) Investigating Popcorn

Material: popcorn kernels, cooking oil, dropper, spring-type clothespin, safety goggles, candle (or other flame source), popsicle stick, heat resistant test tube, aluminum foil.

In this investigation we will use heat to pop a corn kernel. Safety goggles should be worn.
1. Use the clothes pin as a holder for the test tube. Make a cap for the test tube from the aluminum foil.
2. Place aluminum foil under the candle. The thick food-warming candles work best.
3. Place two drops of cooking oil into each test tube.
4. Put one corn kernel into each test tube and place the tube over the candle, keeping it about 3 cm above the flame. Always point the top of the tube away from people.
5. Shake the tube gently to help keep the kernel from burning.
6. Read the questions below and answer them as you wait for the kernel to pop.
7. Observe what happens before the kernel finally pops.
8. After popping, extinguish the candle and let the tube cool. Finally, use the popsicle stick (maybe cut in half lengthwise) to pull out the popped corn.

QUESTIONS/CONCLUSIONS

1. What would happen to the test tube if it was placed in the candle flame?
2. Did you observe any changes in the corn kernel? Were the changes sudden?
3. How did you cause the changes?
4. Why did the corn kernel explode?
5. Occasionally a corn kernel does not pop. Explain why.
6. Has the corn kernel gained weight?
7. What will happen if you first poke a hole in the kernel and then try to pop it? Try this experiment.
8. What would happen if you soaked the kernels for a day before popping and then tried to pop them?

### 3-4) Flying napkin

Material: matches, napkin (newspaper, try other things) , 10 cm x 10 cm sheet of aluminum foil.
1. Place sheet of foil on table.
2. Roll up the newspaper so that it is about 3 cm in diameter and 15 cm high. Use a paper clip on the bottom to hold it together and stand it upright on the foil.
3. Light the match, and then light the newspaper at the top.
4. Observe the newspaper as it burns.

QUESTIONS/CONCLUSIONS

1. Does the flame create currents in the air?
2. How do currents and winds move particles?
3. Are currents responsible for lifting the napkin particles in the air?

### 3-5) Summer and winter colors

Material: 2 identical cans (one painted white, the other black), water, 2 thermometers, flood light.
1. Fill the two cans (either Pepsi, or tin cans) with an equal amount of water.
2. Place a thermometer in each of the cans.
3. Put the cans a few inches apart on a table.
4. Place a flood light an equal distance away from each of the two cans.
5. Leave the light on for five minutes.
6. Turn the light off and check the temperature of the cans.

QUESTIONS/CONCLUSIONS

1. Is black a color?
2. Is white a color?
3. Does color effect the absorption of heat? Why?
4. What colors would be good to wear in the winter to stay warm?
5. What colors would be good to wear in the summer to stay cool?

### 3-6) Heat Absorption by Can Surface

Material: open ended can, candle, heat source, matches, 2 pennies.

1. Place candle on table, and light candle.
2. Using flame, blacken part of the interior of the can (tin can) at about the height of the candle.
3. Using hot wax from the candle, attach the two pennies to the can on opposite sides, with one penny near the blackened area of the can.
4. Wait a few seconds for wax to solidify.
5. Place the can on the table, with the candle (or a hotter heat source) centered inside of it.
6. Note which penny falls first.

QUESTIONS/CONCLUSIONS

1. Which penny fell off first?
2. Which side of the can was hotter?
3. What does this tell you about the importance of color?

### 3-8) Cold gas

Material: aerosol can (Lysol, Pledge, Off or first aid spray).

1. Note how warm the outside of the aerosol can feels.
2. Spray same aerosol on your arm.
3. Compare how the temperature of the gas feels compared to the can.

QUESTIONS/CONCLUSIONS

1. Pressing down on ice causes it to melt. What can you infer about pressure and temperature?
2. If increasing pressure increases the temperature of a gas, what will decreasing pressure do?
3. Does the spray feel cooler than the can? Why?
4. Does the pressure of the can change when you use it? Why?