Across
1
Fourth state of matter
4
Unit of energy
7
Push or pull on an object
8
Our home planet
9
Path of a planet around the sun
12
Unit of electric potential
Down
2
Mass per unit volume
3
Reddish electrical conductor
5
Gas essential for breathing
6
Gas form of a liquid
10
Particle of light
11
Icy body with a tail near the sun