Across
1
Substance with pH above 7
3
Force that attracts objects together
6
Icy body with a tail near the sun
8
Gas essential for breathing
9
Group of similar cells
10
Nerve cell in the brain
14
Chemical element in table salt
Down
2
Gas form of a liquid
4
Compound containing oxygen
5
Form of thermal energy
7
Unit of energy
11
Amplified beam of light
12
Preserved remains of ancient life
13
Infectious microscopic agent