What is thermal expansion and how does it relate to heat?

"The idea behind thermal expansion is that gases expand as the temperature increases. If you have a balloon and you heat up the contents, the balloon will get larger. Scientists use the term ideal gas law to describe this activity. Liquids expand and contract, too, but there is a lot less change than in gases."

I don't know if this is what u meant, but, hope this helps :3

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.

i think the answer is a and b

i wish you luck