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Heat Rising (Melissa Savage)

Author


Melissa Savage, Granada Hills Charter High School

Principle(s) Illustrated

  1. Density of Gas
  2. Convection

Standards

  • Chemistry 4c. Students know how to apply the gas laws to relations between the pressure, tem­ 

    perature, and volume of any amount of an ideal gas or any mixture of ideal 

    gases. 

  • Physics 3c. Students know the internal energy of an object includes the energy of random 

    motion of the object’s atoms and molecules, often referred to as thermal energy. 

    The greater the temperature of the object, the greater the energy of motion of the 

    atoms and molecules that make up the object. 

Procedures

  1. Remove the staple, label and string from the teabag.

  2. Pour out the tea.

  3. Unfold the teabag and stretch it out.

  4. Use your finger to turn the teabag into a cylinder.

  5. Stand the cylinder on one of its end on a plate on a flat surface.

  6. Use a lighter or match to ignite the top of the tea bag cylinder.

  7. Wait a few seconds.

  8. Watch the rocket fly into the air!

Questioning Script

Prior knowledge & experience:

Tea bags cant fly. Have seen hot air balloons.

Root question:

What will happen to the Tea bag when you light it on fire?

Is it possible to make a tea bag float?

Target response:

The flame created by burning the teabag heated the air inside the teabag cylinder. When the air was heated energy was transferred to individual pieces of air called air molecules. The air molecules moved around more quickly and spread out to take up more space. This means that the air molecules were further apart from each other and therefore the air was less dense. The warmer, less dense air rose above the cooler, denser air.

When the teabag burned, the teabag turned into ash and smoke. The smoke lifted away and all that was left was the ash. Ash is light, so it doesn’t require much force to lift it. The rising of the less dense (heated) air inside the teabag had enough force to lift the ash of the teabag.

Common Misconceptions:

All gases have the same mass and density



Connections to Real World

Hot air balloons work in a similar way. Hot air balloons have a burner beneath a balloon envelope. The burner uses propane to heat the air inside the balloon envelope. As the air inside the balloon envelope is heated, the air inside the balloon envelope becomes less dense. As a result, the less dense (heated) air in the balloon envelope rises above the denser (cooler) air surrounding the balloon.



Videos

How to make a tea bag float


References

Floating Tea Bag

Science Kids

Science Squad
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Melissa Savage,
Dec 14, 2011, 8:22 PM
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Melissa Savage,
Dec 14, 2011, 8:19 PM
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