Across
1
Second lightest element
6
Tectonic landmass section
7
Gas form of a liquid
8
Icy body with a tail near the sun
9
Fourth state of matter
11
Force that attracts objects together
Down
2
Biological catalyst
3
Mass per unit volume
4
Our home planet
5
Molten rock beneath Earth surface
10
Unit of energy
12
Ball of burning gas in space