What pulls molecules together?

The Dipole-dipole forces are the attractive forces that hold polar molecules together. This attraction is caused when the partially negative side of one molecule interacts with the partially positive side of another. As you can see, the three polar N-F bonds are all pointing in the same direction.

Explanation:

Dipole-dipole

Explanation:

energy and particles

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".