Across
1
Compound containing oxygen
4
Gas essential for breathing
5
Curved glass that refracts light
6
Natural satellite of Earth
8
Nerve cell in the brain
9
Fourth state of matter
Down
2
Biological catalyst
3
Element found in all living things
4
Path of a planet around the sun
7
Substance with pH above 7
10
Form of thermal energy
11
Chemical element in table salt