Nail polish remover commonly contains a chemical called acetone. It is a well known substance that is good for dissolving many things, some of which are in nail polish. The size of acetone is very small, which makes it easily integrable into the spaces of the larger molecules in nail polish. In fact, acetone is used as one of the solvents for nail polish such that nail polish stays in liquid form. When the polish is applied to a nail, the acetone evaporates quickly, and the polish becomes dry. The large molecules in the polish now interact more strongly with one another and becomes a solid film.

When a remover is applied to dried polish, acetone is essentially allowed to re-enter the spaces between larger molecules in the nail polish, and begins to disrupt the large-molecule interactions, thereby re-dissolving and allowing the polish to be wiped/washed away. This process applies to other substances used as nail polish removers, such as ethyl acetate and isopropyl alcohol. Strictly speaking, the interaction between the polish and the remover is not a chemical one - no chemical bonds are broken or formed in the process; the dissolving process is only physical.

The active ingredient in nail polish remover is acetone (chemical formula C₃H₆O). The reaction which occurs is a dissolution reaction, which is a reaction, but different from a chemical reaction.

The acetone gets between the polymer chains of the polish, breaking up the polish and suspending the molecules in a liquid which can easily be wiped off. This is purely a physical change though; there are no chemical changes taking place (no new chemical species are formed).

The primary ingredient in nail polish remover is acetone, which gives it that distinctive smell. Acetone is a common solvent used in labs (though in much higher concentrations) that is good at cleaning chemical residues off of glassware, for example.

acetone

Acetone is a great general solvent because of its molecular structure (shown below). You may be familiar with the phrase "like dissolves like" , referring to the fact that non-polar molecules (molecules with lots of C-H bonds) are good at dissolving non-polar compounds, while polar molecules (which contain oxygen, sulfur, chloride, etc.) are good at dissolving other polar compounds.

Acetone is a small molecule that has very non-polar and polar properties simultaneously. Its polar C=O bond makes it miscible (soluble) in water, while its non-polar methyl (CH₃) groups can interact with non-polar compounds. This is why a non-polar substance like wax is hard to remove with water, but goes away easily when you use a solvent like acetone.

Nail polish has a number of ingredients, one of which is resin, which can be very non-polar (think of tree sap, for example). This is why acetone can remove nail polish even though water can't.

It varies, but nail polish is usually a polymer that dissolves in an organic solvent that leaves the polymer behind when the solvent evaporates. Generally you want an organic solvent to re-dissolve the polymer in order to remove it. According to Wikipedia, acetone is the most common one used, but ethyl acetate is sometimes used instead because it is less toxic (in particular, acetone will dissolve you as well as the polish if you aren't careful!).

Nail polish remover is a liquid that dissolves nail polish, like water dissolves sugar or salt. It's not so much a chemical reaction as just a liquid or solvent that the nail polish is soluble in. My bottle of nail polish remover has mostly acetone and water, but the article below suggests that ethyl acetate is probably safer than acetone.