Across
1
Gas form of a liquid
4
Gas essential for breathing
5
Biological catalyst
8
Path of a planet around the sun
9
Fourth state of matter
10
Absolute temperature scale unit
Down
2
Element found in all living things
3
Naturally occurring inorganic solid
6
Unit of energy
7
Form of thermal energy
11
Measure of matter in an object
12
Substance with pH below 7