Question

unit review - matter and change
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how is this substance classified? it has the formula $ce{h_{2}o_{2}}$.
a compound
an element
a heterogeneous mixture
a homogeneous mixture

Explanation:

A compound is a pure substance made of two or more different elements chemically bonded together. $\text{H}_2\text{O}_2$ (hydrogen peroxide) consists of hydrogen and oxygen atoms chemically combined in a fixed ratio, matching this definition. An element is a single type of atom, mixtures have physically combined substances (no fixed chemical formula), so these do not apply.

Answer:

a. a compound