Across
1
Fourth state of matter
5
Gas essential for breathing
6
Particle of light
7
Measure of matter in an object
10
Molten rock beneath Earth surface
Down
2
Hottest planet in solar system
3
Curved glass that refracts light
4
Naturally occurring inorganic solid
8
Unit of energy
9
Smallest unit of an element
11
Ball of burning gas in space