Across
1
Substance with pH above 7
4
Chemical element in table salt
6
Unit of force
7
Force that attracts objects together
8
Basic unit of life
9
Our home planet
13
Mass per unit volume
Down
2
Path of a planet around the sun
3
Reddish electrical conductor
5
Blocking of light by a celestial body
10
Infectious microscopic agent
11
Gas essential for breathing
12
Fourth state of matter