Across
1
Unit of energy
4
Positive particle in nucleus
5
Preserved remains of ancient life
6
Mass per unit volume
7
Group of similar cells
9
Disturbance that transfers energy
11
Amplified beam of light
12
Hottest planet in solar system
Down
2
Compound containing oxygen
3
Solid with repeating atomic pattern
8
Naturally occurring inorganic solid
10
Form of thermal energy