Across
1
Chemical element in table salt
4
Unit of power
5
Unit of energy
9
Second lightest element
12
Blocking of light by a celestial body
Down
2
Molten rock beneath Earth surface
3
Curved glass that refracts light
6
Absolute temperature scale unit
7
Gas form of a liquid
8
Biological catalyst
10
Gas essential for breathing
11
Path of a planet around the sun