Across
1
Push or pull on an object
3
Fourth state of matter
4
Gas essential for breathing
5
Mass per unit volume
7
Second lightest element
8
Element found in all living things
10
Curved glass that refracts light
Down
2
Center of an atom or cell
3
Particle of light
4
Path of a planet around the sun
6
Compound containing oxygen
9
Solid with repeating atomic pattern
11
Natural satellite of Earth