Across
1
Naturally occurring inorganic solid
4
Substance with pH below 7
5
Gas essential for breathing
8
Group of similar cells
9
Element found in all living things
10
Infectious microscopic agent
Down
2
Fourth state of matter
3
Precious yellow metallic element
6
Compound containing oxygen
7
Path of a planet around the sun
11
Curved glass that refracts light
12
The Red Planet