Across
1
Icy body with a tail near the sun
4
Particle of light
5
Tissue that contracts for movement
7
Disturbance that transfers energy
9
Group of similar cells
Down
2
Natural satellite of Earth
3
Smallest unit of an element
4
Fourth state of matter
6
Push or pull on an object
7
Unit of power
8
Mass per unit volume
10
Substance with pH below 7
11
Basic unit of life