Across
1
Curved glass that refracts light
3
Element found in all living things
5
Path of a planet around the sun
6
Gas essential for breathing
9
Gas form of a liquid
11
Reddish electrical conductor
12
Preserved remains of ancient life
Down
2
Substance with pH above 7
4
Particle of light
7
Unit of force
8
Ball of burning gas in space
10
Force that attracts objects together