Across
1
Particle of light
4
Natural satellite of Earth
7
Substance with pH above 7
8
Group of similar cells
9
Molten rock beneath Earth surface
Down
1
Fourth state of matter
2
Curved glass that refracts light
3
Our home planet
5
Unit of electric potential
6
Path of a planet around the sun
10
Tissue that contracts for movement
11
Measure of matter in an object
12
Center of an atom or cell