what are 3 ways to change the density of a substance?

Answer 1

Increase temperature. The expansion decreases density.
Decrease temperature. The contraction decreases density.
Apply pressure. The compression increases density.
Reduce pressure. The expansion decreases density.
Increase relative velocity. Increase in relative velocity increases density. (this is relatavistic, may not be in "classical physics" texts)
Decrease relative velocity. Decrease in relative velocity decreases density. (ditto on the relatavistic thing)
Nuclear fusion. Fusion of atoms increases density.
Nuclear fission. Fission of atoms decreases density.
Apply electrical charge. Conducting an electrical charge decreases density.
Reduce electrical charge. This increases density.
Increase proximity to other mass. The gravitational well effect increases density. (again a relatavistic effect)
Decrease proximity to other mass. Decreases density (yet again a relatavistic effect.)

Hmm.... that's 12. Enough? :)

Answer 2

Heat it, cool it, or combine it with something else (dilute it).

Answer 3

Burn it or cool it off... can't think of another for now.

Answer 4

freeze it.....melt it.....evaporate it...?

Answer 5

Dilute, crush, burn ????????????