Across
1
Gas form of a liquid
3
Unit of heredity
7
Positive particle in nucleus
8
Smallest unit of an element
9
Curved glass that refracts light
Down
2
Disturbance that transfers energy
4
Reddish electrical conductor
5
Force that attracts objects together
6
Unit of force
10
Path of a planet around the sun
11
Ball of burning gas in space