Vinegar is a common household liquid, a fermented product used widely in cooking and cleaning. Many people assume it freezes at the same temperature as water, 32°F (0°C). However, the presence of dissolved molecules prevents vinegar from solidifying at this temperature, a common characteristic of mixtures.
The Primary Components of Vinegar
Vinegar is chemically defined as a dilute aqueous solution of acetic acid. Water makes up the majority of the liquid, but dissolved acetic acid gives vinegar its distinctive sour taste and pungent smell. The concentration of this acid is the most important factor determining the liquid’s properties, including its freezing point.
Most household white distilled vinegar contains between 5% and 8% acetic acid by volume. Higher concentrations, such as 10% or 20% cleaning vinegars, are available for tougher tasks. Because the ratio of water to acid is variable, not all vinegars freeze at the exact same temperature.
Understanding Freezing Point Depression
Vinegar remains liquid below the freezing point of pure water due to a concept known as freezing point depression. This is a colligative property, meaning it depends on the number of solute particles dissolved in the solvent, not the identity of those particles. The acetic acid molecules act as the solute in this water-based solution.
These dissolved acid molecules interfere with water molecules forming an organized crystalline structure. The presence of acetic acid disrupts the hydrogen bonding necessary for the water to solidify. Consequently, a lower temperature is required to slow the water molecules enough to overcome this disruption and allow crystallization.
Typical Freezing Points by Concentration
The freezing point of vinegar is directly related to its acetic acid concentration. Standard household white vinegar (approximately 5% acetic acid) typically begins to freeze around 28°F (-2°C). This is four degrees Fahrenheit lower than pure water’s 32°F freezing point.
As the concentration of acetic acid increases, the freezing point continues to drop. A 10% or higher concentration of vinegar would freeze at a temperature even lower than 28°F. This trend holds true until the solution becomes almost pure acetic acid.
The purest form of the chemical, known as glacial acetic acid, presents a unique exception to this trend because it contains almost no water. This highly concentrated substance (near 100% acetic acid) freezes at a relatively warm temperature of about 62°F (17°C). It is called “glacial” because it forms ice-like crystals at this temperature, which is well above the freezing point of water.
Practical Implications of Freezing Vinegar
When vinegar is exposed to temperatures below its freezing point, the water component freezes first. This process separates the mixture, concentrating the remaining liquid acetic acid. If the vinegar is only partially frozen, the slushy liquid portion will be noticeably more acidic than the original solution.
Freezing does not ruin vinegar for consumption or cleaning, and it is safe to use once it has thawed completely. However, the texture and clarity may change slightly upon thawing, so it is important to mix the contents well to restore the original concentration. To avoid accidental freezing and potential container breakage due to expansion, vinegar should be stored in an area where the temperature remains above 28°F.