Chemical bonds play a big role in how energy changes during reactions.

Let’s break it down into two main types of reactions:

1. Exothermic Reactions:

   • These reactions give off energy, usually as heat.
   • For example, when methane burns, it gives off about 890 kilojoules of energy for each mole.

2. Endothermic Reactions:

   • These reactions take in energy from the environment.
   • A good example is when ammonium nitrate dissolves, it absorbs about 25 kilojoules of energy for each mole.

In simple terms, the energy from breaking bonds (endothermic) and the energy from making new bonds (exothermic) together affect the overall change in energy during a chemical reaction.