Across
1
Icy body with a tail near the sun
2
Disturbance that transfers energy
4
Gas form of a liquid
6
Second lightest element
8
Group of similar cells
11
Positive particle in nucleus
12
Absolute temperature scale unit
Down
2
Unit of power
3
Particle of light
5
Compound containing oxygen
7
Fourth state of matter
9
Form of thermal energy
10
Substance with pH below 7