Across
1
Mass per unit volume
6
Compound containing oxygen
8
Form of thermal energy
9
Nerve cell in the brain
10
Disturbance that transfers energy
12
Ball of burning gas in space
Down
2
Substance with pH below 7
3
Center of an atom or cell
4
Chemical element in table salt
5
Solid with repeating atomic pattern
7
Unit of force
11
Second lightest element