Across
1
Nerve cell in the brain
5
Disturbance that transfers energy
7
Our home planet
8
Naturally occurring inorganic solid
10
Gas essential for breathing
11
Chemical element in table salt
Down
2
Curved glass that refracts light
3
Unit of energy
4
Absolute temperature scale unit
6
Ball of burning gas in space
9
Center of an atom or cell
12
Second lightest element