Across
1
Icy body with a tail near the sun
4
Particle of light
5
Gas form of a liquid
6
Substance with pH below 7
8
Curved glass that refracts light
9
Molten rock beneath Earth surface
Down
1
Element found in all living things
2
The Red Planet
3
Force that attracts objects together
4
Fourth state of matter
7
Path of a planet around the sun