Across
1
The Red Planet
3
Mass per unit volume
5
Curved glass that refracts light
6
Chemical element in table salt
7
Element found in all living things
9
Unit of electric potential
11
Push or pull on an object
Down
1
Molten rock beneath Earth surface
2
Group of similar cells
4
Amplified beam of light
8
Positive particle in nucleus
10
Gas essential for breathing
12
Unit of force