Across
1
Particle of light
3
Substance with pH below 7
4
Force that attracts objects together
7
Basic unit of life
10
Second lightest element
11
Natural satellite of Earth
Down
1
Tectonic landmass section
2
Mass per unit volume
5
Absolute temperature scale unit
6
Fourth state of matter
8
Unit of energy
9
Magnetic metallic element
12
Disturbance that transfers energy