Across
1
Preserved remains of ancient life
3
Gas essential for breathing
6
Substance with pH below 7
9
Particle of light
11
Curved glass that refracts light
12
Substance with pH above 7
Down
1
Push or pull on an object
2
Solid with repeating atomic pattern
4
Force that attracts objects together
5
Center of an atom or cell
7
Smallest unit of an element
8
Mass per unit volume
10
Path of a planet around the sun
13
Disturbance that transfers energy