Across
1
Substance with pH below 7
3
Absolute temperature scale unit
5
Magnetic metallic element
7
Ball of burning gas in space
8
Naturally occurring inorganic solid
12
Preserved remains of ancient life
Down
2
Mass per unit volume
4
Nerve cell in the brain
6
Fourth state of matter
9
Glass that splits light into spectrum
10
Second lightest element
11
Gas essential for breathing