Calorimetry
Calorimetry is measuring how much heat energy is stored inside something, like a nut, by burning it.
Think of it this way
You heat a pot of water on the stove. You drop a burning nut into the water. The water warms up, and you measure that temperature rise. The bigger the rise, the more heat energy was stored in the nut.
Explaining calorimetry by grade level
When you burn a peanut, it gives off heat. That heat can warm up water. The more the water warms up, the more energy was in the peanut. A cashew might warm the water even more, because it holds more energy inside.