Across
1
Fourth state of matter
4
Hottest planet in solar system
7
Biological catalyst
10
Unit of electric potential
11
Preserved remains of ancient life
Down
2
Second lightest element
3
The Red Planet
5
Substance with pH above 7
6
Force that attracts objects together
8
Center of an atom or cell
9
Push or pull on an object
12
Compound containing oxygen
13
Mass per unit volume