Across
1
Measure of matter in an object
3
Path of a planet around the sun
6
Particle of light
8
Molten rock beneath Earth surface
11
Unit of force
12
Blocking of light by a celestial body
Down
2
Second lightest element
4
Smallest unit of an element
5
Group of similar cells
7
Element found in all living things
9
Unit of heredity
10
Form of thermal energy