Which substance cannot be broken down by a chemical change? a) butanal b) propene c) gold d) water

C) Gold

Explanation:

Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Gold

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass. It can be decomposed into simpler constituents using chemical reactions. Example: water , butanal , and propene

For example:

Thus the element gold can not be broken down by a chemical change.