Across
1
Gas form of a liquid
4
Preserved remains of ancient life
5
Second lightest element
7
Nerve cell in the brain
8
Force that attracts objects together
9
Hottest planet in solar system
Down
2
Magnetic metallic element
3
Smallest unit of an element
6
Mass per unit volume
7
Center of an atom or cell
10
Curved glass that refracts light