Across
1
Gas essential for breathing
5
Naturally occurring inorganic solid
6
Unit of heredity
8
Hottest planet in solar system
9
Icy body with a tail near the sun
10
Curved glass that refracts light
12
Glass that splits light into spectrum
Down
2
Mass per unit volume
3
Blocking of light by a celestial body
4
Positive particle in nucleus
7
Disturbance that transfers energy
9
Basic unit of life
11
Substance with pH below 7
13
Natural satellite of Earth