Across
1
Unit of power
3
Force that attracts objects together
4
Mass per unit volume
6
Basic unit of life
7
Tissue that contracts for movement
10
Natural satellite of Earth
11
Blocking of light by a celestial body
Down
2
Positive particle in nucleus
5
Naturally occurring inorganic solid
8
Nerve cell in the brain
9
Form of thermal energy
12
Substance with pH above 7