Acetone, chemically known as propanone, is a simple organic compound that serves as a widely used solvent. It is a colorless, flammable liquid recognized for its characteristic, slightly pungent odor. As a small ketone molecule, it exhibits a high degree of volatility, meaning it readily turns into a gas. Understanding the specific temperature at which this phase change occurs is fundamental to its safe handling and application.
The Specific Boiling Point Value
The standard boiling point of pure acetone is precisely \(56.05^{\circ} \text{C}\) (approximately \(133^{\circ} \text{F}\)) at standard atmospheric pressure. The boiling point is the temperature at which the liquid’s vapor pressure equals the surrounding atmospheric pressure. Once this equilibrium is reached, the liquid transforms into a gas throughout its entire bulk. This temperature is significantly lower than that of water, which boils at \(100^{\circ} \text{C}\) (\(212^{\circ} \text{F}\)).
Understanding Acetone’s Volatility
Acetone’s relatively low boiling temperature is a direct indicator of its high volatility, which is a major factor in its utility as a solvent. This low boiling point is a consequence of the weak intermolecular forces between acetone molecules, primarily dipole-dipole attractions. Because these forces are easily overcome, the liquid does not require a large input of thermal energy to change into a gas.
The high volatility means acetone evaporates quickly at room temperature, making it ideal for processes requiring rapid drying. This quick evaporation is highly desirable in applications such as cleaning and degreasing agents, where a residue-free surface is needed almost immediately. This rapid phase change allows the solvent to dissolve substances and then disappear quickly from the substrate.
How External Conditions Affect Boiling
The standard boiling point is a fixed reference, but the actual temperature at which acetone boils can shift based on environmental conditions. One of the most influential factors is the external atmospheric pressure, which changes based on altitude. At higher elevations, the lower atmospheric pressure causes acetone to boil at a temperature below \(56^{\circ} \text{C}\). Conversely, boiling acetone in a sealed container or under higher pressure requires a higher temperature to achieve the necessary vapor pressure.
The purity of the acetone also introduces a change to its boiling behavior. The presence of non-volatile impurities, such as dissolved solids, will generally increase the boiling point, a phenomenon known as boiling point elevation. This occurs because impurities interfere with the solvent molecules’ ability to escape into the vapor phase, requiring a higher temperature. If acetone is mixed with another volatile liquid, the resulting mixture may boil over a range of temperatures instead of a single point.