Q: Answer the following question given this paragraph: When studying the different states that matter exhibits, we have been looking at pure substances . Pure substances have a constant composition and can only be changed through chemical reactions. Constant composition indicates that a sample of a pure substance always contains the same elements in the same proportions. There are two main types of pure substances:. Q: Pure substances have a constant composition and can only be changed through what? A:

Options are:
a). heating;
b). dissolution;
c). liquid reactions;
d). chemical reactions;
A:
d).