Across
1
Gas essential for breathing
4
Amplified beam of light
7
Basic unit of life
9
Tissue that contracts for movement
10
Molten rock beneath Earth surface
12
Measure of matter in an object
Down
2
Precious yellow metallic element
3
Element found in all living things
5
Curved glass that refracts light
6
Biological catalyst
8
Substance with pH below 7
11
Force that attracts objects together
12
The Red Planet