Do chemical changes involve energy?
Energy is involved in the formation of chemical bonds and also when existing bonds are broken.
Chemical changes involve the breaking of existing bonds and the creation of new bonds, consider the following reaction.
During the reaction, the single covalent bonds in the H-H molecules and the double covalent bonds in the O=O molecules are broken. The of process of breaking bonds uses energy.
When water (H-O-H) is formed, new single bonds are formed between H and O atoms. This process results in energy being given off.
The net result of this reaction is that a large amount of energy will be given off because the amount of energy required to break the bonds of the H-H and the O=O molecules is less than the energy given off when water forms. There are numerous videos on YouTube showing this reaction.