Heat capacity is a measure of how much heat energy is needed to make an object or substance get warmer (literally its capacity to store heat). It’s like how much food you need to eat to make you feel full. Some things, like metal, need only a little bit of heat to make them hotter, while others, like water, need a lot more heat to get warmer. Heat capacity is like the size of the bucket that you use to carry water from one place to another: a bigger bucket can carry more water, and a higher heat capacity means that it takes more heat to warm something up.