Across
1
Second lightest element
5
Substance with pH below 7
6
Preserved remains of ancient life
7
Amplified beam of light
9
Smallest unit of an element
12
Mass per unit volume
Down
2
Force that attracts objects together
3
Blocking of light by a celestial body
4
Fourth state of matter
8
Naturally occurring inorganic solid
10
Solid with repeating atomic pattern
11
Natural satellite of Earth
13
Measure of matter in an object