Across
1
Mass per unit volume
5
Naturally occurring inorganic solid
8
Gas form of a liquid
9
Preserved remains of ancient life
10
Curved glass that refracts light
11
Natural satellite of Earth
12
Our home planet
Down
2
Substance with pH below 7
3
Positive particle in nucleus
4
Second lightest element
6
Unit of energy
7
Center of an atom or cell
13
Element found in all living things