Across
1
Center of an atom or cell
2
Ball of burning gas in space
4
Path of a planet around the sun
6
Substance with pH below 7
9
Compound containing oxygen
12
Curved glass that refracts light
Down
2
Chemical element in table salt
3
Glass that splits light into spectrum
5
Basic unit of life
7
Gas form of a liquid
8
Magnetic metallic element
10
Tissue that contracts for movement
11
Measure of matter in an object