Across
1
Mass per unit volume
4
Tissue that contracts for movement
8
Unit of power
9
Preserved remains of ancient life
10
Path of a planet around the sun
13
Curved glass that refracts light
Down
2
Precious yellow metallic element
3
Element found in all living things
5
Solid with repeating atomic pattern
6
Measure of matter in an object
7
Ball of burning gas in space
11
Natural satellite of Earth
12
Substance with pH below 7