Across
1
Gas form of a liquid
2
Curved glass that refracts light
4
Measure of matter in an object
5
Nerve cell in the brain
9
Unit of energy
11
Reddish electrical conductor
12
Ball of burning gas in space
Down
1
Infectious microscopic agent
3
Fourth state of matter
6
Center of an atom or cell
7
Our home planet
8
Group of similar cells
10
Precious yellow metallic element