Across
1
Form of thermal energy
3
Blocking of light by a celestial body
8
Unit of power
9
Substance with pH above 7
10
Gas essential for breathing
12
Chemical element in table salt
Down
2
Biological catalyst
4
Curved glass that refracts light
5
Our home planet
6
Nerve cell in the brain
7
Ball of burning gas in space
11
Group of similar cells