Question

Classify these substances. More than one answer may apply in each case.

Answer 1

Answer: $H_2$ :  Pure substance, Element

$O_2$ : Pure substance , Element

$H_2O$:  Pure substance, Compound

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: $H-2$ and $O_2$

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: $H_2O$

Heterogeneous Mixture : Mixture that has its different components mixed unevenly within the substance . Example: Air

Homogeneous Mixture : Mixture that has its different components mixed evenly within the substance. Example: sugar dissolved in water