Thermal Energy Transfer (Summer Barlow)

Title: Fireproof Cup/Fireproof Balloon

Principle(s) Investigated: thermal energy, heat transfer, conduction, and specific heat of water

Standards: MS-PS3-3 Energy: Apply scientific principles to design, construct, and test a device that either minimizes or maximizes thermal energy transfer.

Materials: Part 1: paper cups, water, tea bag, safety goggles, tongs, candle/flame, match, stand, ring, clamp, and container with water

Part 2: balloons, safety goggles, candle/flame, match, container, and water

Procedure:

-Set up equipment for part 1 of the experiment/put on safety goggles

-Light the candle and place the paper cup filled with water above it until the water boils/remove it from the flame (tell students you are making a cup of tea)

-Put an empty paper cup above the flame (use the tongs) [the cup should ignite/when it does, remove it from the flame and place it into a container of water until the flame is put out]

-Ask students why one of the cups ignited and why the other one did not (have students draw out models to explain their ideas/have them share out their ideas and explain their reasoning)

-Go over why this happened/discuss the specific heat of water

-Clean up part 1 of the experiment

-Set up equipment for part 2 of the experiment (safety goggles should still be on)

-Light the candle and blow up a balloon/tell students your are going to put the balloon near the flame

-Have students predict what they think might happen

-Perform the experiment (the balloon should pop)

-Blow up a second balloon, but put water into it as well

-Have students predict what they think might happen this time when putting the balloon near the flame

-Perform the experiment (the balloon should not pop, soot should appear on the bottom of the balloon [carbon])

-Ask students why the first balloon popped and why the second one did not/have them draw out models to explain their reasoning

-Have students share out their ideas/explain their reasoning

-Discuss why this happens (water absorbs heat)

-Review/have students share out something new they learned

-Clean up materials

Student prior knowledge: Prior to this experiment/lesson, students should have knowledge of particles, kinetic energy, potential energy, heat, and thermal energy. They should know that heat is what we get when kinetic energy transfers one object to another (warm object to a cooler object). Students should also know that thermal energy is heat energy. Thermal energy is the total potential and kinetic energy of the particles that make up an object.

Explanation:

Part 1: The first paper cup that is heated contains water. When the cup is heated, the water conducts/absorbs the heat. This causes the water to heat up and boil. Once the water in the first cup reaches its boiling point (100 degrees celsius), it will start to evaporate (turn into steam). A thermal energy transfer takes place. Meanwhile, the cup is not able to reach its ignition point and does not catch on fire. (Paper burns at 233 degrees celsius.) Different things warm up at different rates. The specific heat of something has to do with the amount of heat needed to increase the temperature by one degree. Water happens to have a high specific heat capacity. The specific heat capacity of water is 4182 J/kg degrees celsius. This is equivalent to 1 calorie/gram degrees celsius. On the other hand, the specific heat capacity of paper is 1336 J/kg degrees celsius and 0.32 calories/gram degrees celsius. In other words, water requires more energy to heat up. When the second paper cup is heated without water, it heats up and is able to reach its ignition point. Therefore, the cup catches on fire.

Part 2: The first balloon (filled with air) heats up until it pops. The second balloon (filled with both air and water) also begins to heat up. The heat passes through the balloon and is once again absorbed by the water. (The water conducts the heat away from the balloon.) The water near the heat (flame) heats up until it rises. The cooler water sinks and is heated up until it rises too. The process continues to repeat. This time around, the water prevents the balloon from popping. The flame on the balloon then creates soot (carbon).

Questions & Answers:

1) Why did the cup with water not catch fire?

Answer: The water which has a high heat capacity absorbed the heat. This caused the water to heat up and boil, rather than the cup reaching its ignition point and catching on fire.

2) Why did the balloon with water not pop?

Answer: The water again absorbed the heat so the balloon would not get hot enough to pop.

3) What do you think would happen if we used a plastic cup instead of a paper cup and put the flame at the top of the cup?

Answers may vary. (Example: The plastic cup would burn down to the point where the water is. The rest of the cup would not burn because the water would absorb the heat. As a result, the water would heat up.)

Applications to Everyday Life:

1) This experiment relates to firefighting. Firefighters will sometimes coat houses with a water-absorbing polymer foam. When the fire gets to the house, the water in the foam helps to absorb the heat and control it. Because of this, firefighters have a little bit of extra time to put out the fire.

2) This experiment also relates to the human body and sweat. Our body uses water to manage the heat and the increase in temperature that occurs when we exercise. Instead of overheating, the sweat being released evaporates. As a result, our body cools down.

3) One last thing that this experiment relates to is the ocean/beach. When there are high temperatures at the beach, the sand often becomes very hot. Although the sand can be extremely hot, the ocean water is not. This relates to the fact that water has a high heat capacity and takes a lot longer to heat up than the sand. The ocean water and the sand heat up at different rates.

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