Question

Does the densoty of an object change if you add more of it because i did an expirement that proved that the density does change so im confused, thx

Answer 1

No the density does not change. Density is a ratio D=m/v no matter how much of a substance you have its mass will be proportional.
When doing density labs sometimes you might get different answers due to errors that are unavoidable.

Answer 2

If your experiment somehow 'proved' that the density of a substance changed, then your experiment was faulty and produced an error result.

The density of a SUBSTANCE doesn't depend on how much of the SUBSTANCE there is.  One drop of the substance has the same density as a supertanker full of the SAME substance.

You just have to be careful that when you add more of it, the stuff that you add is PURE, and doesn't have anything else in it except more of the SAME SUBSTANCE.  If it has something else in it, then the density will APPEAR to change.