Across
1
Absolute temperature scale unit
4
Biological catalyst
6
Center of an atom or cell
8
Second lightest element
11
Ball of burning gas in space
Down
2
Group of similar cells
3
Mass per unit volume
5
Unit of energy
7
Natural satellite of Earth
9
Curved glass that refracts light
10
Push or pull on an object
12
Naturally occurring inorganic solid