system
Given the following post, respond as if you're commenting on Reddit:
human
What causes different materials to expand or contract at different rates?

Recently finished the thermodynamics unit in physics, and wanted to know what causes different materials to expand or contract at different rates? Does it have anything to do with the heat capacity, or are they two separate things?  


\(I am aware that it is called the "coefficient of linear expansion" btw\)
gpt
Intermolecular bonding energy. Heat is atomic kinetic energy, right? Well, if a material is bonded to itself really strongly (tungsten), it will take a lot of energy (heat) to force them to spread out. If they are weak (plastic), they will spread out a lot further with application of the same amount of energy.