Across
1
Second lightest element
3
Path of a planet around the sun
4
Center of an atom or cell
6
Hottest planet in solar system
8
Force that attracts objects together
9
Substance with pH above 7
10
Tissue that contracts for movement
Down
2
Tectonic landmass section
3
Compound containing oxygen
5
Biological catalyst
7
Measure of matter in an object
11
Form of thermal energy