Across
1
Naturally occurring inorganic solid
2
Path of a planet around the sun
5
Tissue that contracts for movement
7
Substance with pH above 7
9
Form of thermal energy
12
Nerve cell in the brain
Down
2
Gas essential for breathing
3
Tectonic landmass section
4
Smallest unit of an element
5
Natural satellite of Earth
6
Curved glass that refracts light
8
Force that attracts objects together
10
Ball of burning gas in space
11
Biological catalyst