Across
1
Force that attracts objects together
4
Center of an atom or cell
6
Tissue that contracts for movement
7
Path of a planet around the sun
8
Basic unit of life
Down
1
Precious yellow metallic element
2
Mass per unit volume
3
Substance with pH above 7
5
Nerve cell in the brain
9
Compound containing oxygen
10
Glass that splits light into spectrum
11
Ball of burning gas in space