Question

Susan is investigating heat transfer using a pan filled with tap water, a bottle, and a balloon.



First, she secures a deflated balloon over the mouth of a 1-liter glass bottle and places it inside a pan.
Then, she transfers the pan to the stove and brings the water to a boil.
Finally, she observes the results of her investigation.


Investigation Setup

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Which explanation describes how heat was transferred from the air inside the bottle to the balloon?



A.
Heat was transferred by condensation, in which air molecules release heat that rises to occupy the balloon and inflates it.

B.
Heat was transferred by radiation, in which the electrons in air atoms emit heat energy that flows up causing the balloon to inflate.

C.
Heat was transferred by convection, in which the molecules of hot air move faster, expand, and reduce density, so they rise and inflate the balloon.

D.
Heat was transferred by conduction, in which the molecules of hot air collide with each other all the way to the top causing the balloon to inflate.

Answer 1

C. Heat was transferred by convection. As the air in the bottle was heated, its molecules moved faster and the air expanded (lowering its density), so the warmer air rose/expanded and pushed into the balloon, inflating it.