When the air inside a hot air balloon is heated, it expands and takes up a larger volume. As a result, it floats higher into the sky. What else happens to the air inside the balloon as it is heated?
a) Density decreases.

b) Density increases.

c) Mass decreases.

d) Mass increases

Question

When the air inside a hot air balloon is heated, it expands and takes up a larger volume. As a result, it floats higher into the sky. What else happens to the air inside the balloon as it is heated?
 a) Density decreases. 

 b) Density increases. 

 c) Mass decreases. 

 d) Mass increases

thomaster · Answer

To make something fly, does it need to be heavier of lighter than air?

anonymous · Answer

lighter?

thomaster · Answer

yes, so what happens to the mass?

anonymous · Answer

It decreases right?

thomaster · Answer

Trick question :) 
The mass stays the same (it actually increases a little bit because you add energy).
The air gets lighter because heating it makes it less dense, so as the question says: the air expands and occupies a larger volume. So the density decreases.

thomaster · Answer

Less dense air experiences a buoyant force in more dense air, like a bubble in water.

anonymous · Answer

Thanks! It helped a lot!

thomaster · Answer

You're welcome :)