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Acetone is an organic chemical compound commonly used in laboratories as a solvent and in commercial products such as nail polish remover. It has a density of about 0.788 grams per milliliter (g/mL) at room temperature, 77°F (25°C). Although acetone exists as liquid at room temperature, it is less dense than water, which has a room temperature density of about 1 g/mL.
The density of acetone, as with other substances, is determined by dividing its mass by its volume. A material with a high density will have a large amount of mass for its volume, while a less dense material will have lower mass per volume. For example, a solid steel ball is denser than a ball of equal size made of styrofoam because, even though the volumes of the balls are the same, the steel has the greater mass.
Acetone’s density is 0.788 g/mL at room temperature, which means that each milliliter of the liquid has a mass of 0.788 grams. The density of acetone, like all density measurements, changes with pressure and temperature. Generally, increased temperature decreases the density of a material, and increased pressure increases density.
Increased temperature causes the density of acetone to decrease because the increased thermal energy causes the acetone molecules to become more energized, spreading them farther apart from one another. The volume of the substance increases, while the mass remains the same. By the density equation, this results in a lowered density — the substance has less mass per unit of volume.
Pressure, on the other hand, causes the density of acetone to increase. As pressure is increased, molecules of the substance crowd closer together. Volume decreases, while mass stays constant. This results in an increase of mass per volume unit.
The specific gravity of acetone is closely related to the density of acetone. The measure of a substance’s specific gravity is given by the density of a substance at a certain temperature and pressure divided by the density of water at the same temperature and pressure. Since water’s density at room temperature and pressure is about 1 g/mL, the density of a substance under those conditions will be very close to its specific gravity. Acetone’s specific gravity is therefore about 0.788 at room temperature and normal atmospheric pressure.
Normally, a substance that has a lower specific gravity than water — lower than 1 — is buoyant and will float to the surface when placed in water. Substances that have a specific gravity of 1 are neutrally buoyant, while those with a specific gravity greater than 1 will sink. Acetone, however, is soluble in water, so it dissolves, creating an acetone-water solution. The density of an acetone-water solution varies depending on the concentration of acetone present.