Across
1
Hottest planet in solar system
2
Particle of light
4
Unit of power
5
Icy body with a tail near the sun
8
Second lightest element
9
Tectonic landmass section
Down
2
Fourth state of matter
3
Mass per unit volume
4
Disturbance that transfers energy
6
Reddish electrical conductor
7
Element found in all living things