Across
1
Reddish electrical conductor
3
Measure of matter in an object
5
Icy body with a tail near the sun
7
Mass per unit volume
10
Unit of power
Down
2
Smallest unit of an element
4
Fourth state of matter
6
Group of similar cells
8
Ball of burning gas in space
9
Force that attracts objects together
11
Hottest planet in solar system