横向
1
Mass per unit volume
5
Form of thermal energy
6
Fourth state of matter
7
Ball of burning gas in space
10
Disturbance that transfers energy
12
Element found in all living things
纵向
2
Push or pull on an object
3
Center of an atom or cell
4
Preserved remains of ancient life
8
Amplified beam of light
9
Substance with pH below 7
11
Gas essential for breathing
13
Our home planet