The products in a decomposition reaction include an element and a compound are compounds are elements can be elements or compounds

I believe the answer is  can be elements or compounds
In this case, elements in the decomposition reaction is the substance that cannot be separated into simpler substances.
Compounds, technically act as a reactant in the decomposition reaction, but since the reaction breakdown one substance into two or more, sometimes it exists in the product.

The kinetic energy of the liquid increases. hope this !