Vinegar is a common household item defined chemically as a solution of acetic acid dissolved in water. Because it is primarily water, the liquid will freeze when exposed to sufficiently cold temperatures. However, it does not solidify at the same 32°F (0°C) temperature as pure water.
Why Vinegar Doesn’t Freeze Like Water
Vinegar resists freezing at the typical temperature of water due to a phenomenon called freezing point depression. This colligative property means that when a solute is added to a solvent, the freezing point of the resulting solution is lowered. In vinegar, the acetic acid molecules act as the solute, interfering with the formation of the ordered crystal structure required to form ice.
Household white vinegar, which typically contains about 5% acetic acid, generally begins to freeze around 28°F (-2°C). This slight difference explains why a bottle of vinegar will remain liquid in conditions that would cause pure water to freeze solid.
How Acetic Acid Concentration Affects Freezing
The exact temperature at which vinegar freezes is directly linked to its acetic acid concentration. The higher the percentage of acetic acid in the solution, the lower the freezing point will be. Stronger cleaning vinegars, which may contain 10% or more acetic acid, are more resistant to freezing than standard 5% white distilled vinegar.
In contrast, pure, concentrated acetic acid, known as glacial acetic acid, freezes at a much warmer temperature of 62°F (16.6°C). This demonstrates that the depression effect is dependent on the ratio of water to acid. When commercial vinegar freezes, it often forms a slush because the water component solidifies first, leaving a more concentrated, unfrozen liquid behind.
Storing and Using Frozen Vinegar
When freezing vinegar, it is important to be mindful of expansion, as the liquid will increase in volume as it solidifies. For this reason, glass containers should not be used, as they may crack or shatter under the pressure of the expanding ice. Instead, transfer the vinegar to a plastic container and leave a small amount of headspace to accommodate the volume change.
Freezing does not significantly affect the chemical properties of vinegar, so it remains safe to use after thawing. While the taste, clarity, or texture may change slightly upon thawing, the efficacy for cooking or cleaning is generally preserved. Frozen vinegar is often stored in ice cube trays, creating convenient portions for use in cooking or for making natural weed-killing or cleaning solutions. To thaw larger quantities, transfer the frozen liquid from the freezer to the refrigerator and allow it to melt slowly overnight.