Across
1
Substance with pH below 7
4
Path of a planet around the sun
5
Disturbance that transfers energy
8
Measure of matter in an object
10
Icy body with a tail near the sun
12
Absolute temperature scale unit
Down
2
Mass per unit volume
3
Unit of power
6
Ball of burning gas in space
7
Substance with pH above 7
9
Smallest unit of an element
11
Group of similar cells