Across
1
Gas essential for breathing
3
Gas form of a liquid
4
Precious yellow metallic element
6
Compound containing oxygen
7
Mass per unit volume
8
Form of thermal energy
9
Center of an atom or cell
Down
1
Path of a planet around the sun
2
Hottest planet in solar system
4
Force that attracts objects together
5
Naturally occurring inorganic solid
10
Basic unit of life
11
Blocking of light by a celestial body