A chemist wants to observe the following reaction:

2H2 + O2 → 2H2O

The chemist is standing inside a room with oxygen in the air and has a balloon filled with hydrogen. The chemist holds a small flame up to the hydrogen balloon. When the balloon pops, the hydrogen explodes in a ball of fire.

explain which part of the reaction is higher in energy

The reactants (hydrogen and oxygen) are higher in energy than the products (water) in this reaction. The energy difference is released as heat and light during the combustion, which is observed as the explosion and ball of fire.