Across
1
Element found in all living things
3
Hottest planet in solar system
4
Mass per unit volume
9
Path of a planet around the sun
10
Glass that splits light into spectrum
11
Unit of heredity
12
Second lightest element
Down
2
Gas essential for breathing
5
Basic unit of life
6
Preserved remains of ancient life
7
Absolute temperature scale unit
8
Molten rock beneath Earth surface