Across
1
Force that attracts objects together
3
Curved glass that refracts light
6
Tectonic landmass section
7
Compound containing oxygen
8
Unit of heredity
10
Natural satellite of Earth
11
Mass per unit volume
Down
2
Measure of matter in an object
4
Second lightest element
5
Blocking of light by a celestial body
9
Group of similar cells
12
Icy body with a tail near the sun