Across
1
Substance with pH above 7
3
Mass per unit volume
4
Disturbance that transfers energy
6
Gas form of a liquid
9
Absolute temperature scale unit
11
Icy body with a tail near the sun
13
Ball of burning gas in space
Down
2
Center of an atom or cell
5
Compound containing oxygen
7
The Red Planet
8
Gas essential for breathing
10
Unit of force
12
Molten rock beneath Earth surface