Across
1
Particle of light
5
Substance with pH above 7
6
Ball of burning gas in space
9
Unit of force
Down
2
Precious yellow metallic element
3
Gas form of a liquid
4
Biological catalyst
7
Smallest unit of an element
8
Icy body with a tail near the sun
10
Hottest planet in solar system
11
Disturbance that transfers energy