Across
1
Curved glass that refracts light
4
Infectious microscopic agent
5
Push or pull on an object
6
Gas essential for breathing
10
Substance with pH above 7
11
Form of thermal energy
12
Absolute temperature scale unit
Down
2
Nerve cell in the brain
3
Center of an atom or cell
7
Ball of burning gas in space
8
Force that attracts objects together
9
Unit of energy