What are exothermic chemical reactions?

An exothermic chemical reaction is when things get warm because a new substance is made.

Imagine you're playing with your favorite building blocks. When you put two pieces together to make something cool, like a tower or a bridge, it feels satisfying, almost like the blocks are happy to be together. In an exothermic reaction, the "blocks" (which are actually tiny particles called atoms) join up and release heat in the process.

Think of making hot chocolate. When you mix cocoa powder with hot water, it gets warm, that’s because energy is being released. In a way, the cocoa and water are like the "blocks" joining together to make something new (the hot chocolate), and they let out heat in the process.

When you light a candle, the wax burns and makes heat and light. That’s an exothermic reaction, too, the wax is changing into new substances (like carbon dioxide and water vapor) while letting out energy as heat and light.

So, next time something gets warm when it changes, remember: there's a happy party going on at the tiny particle level!