Across
1
Ball of burning gas in space
3
Curved glass that refracts light
5
Disturbance that transfers energy
6
Substance with pH below 7
10
Center of an atom or cell
Down
2
Group of similar cells
4
Molten rock beneath Earth surface
7
Hottest planet in solar system
8
Element found in all living things
9
Basic unit of life
11
Precious yellow metallic element
12
Absolute temperature scale unit