Across
1
Amplified beam of light
4
Nerve cell in the brain
6
Second lightest element
9
Disturbance that transfers energy
10
Push or pull on an object
11
Mass per unit volume
12
Substance with pH above 7
13
Unit of electric potential
Down
2
Our home planet
3
Tissue that contracts for movement
5
Gas essential for breathing
7
Precious yellow metallic element
8
The Red Planet
14
Reddish electrical conductor
15
Naturally occurring inorganic solid