Thaw

Thaw is the process by which frozen matter, such as ice or frozen food, changes to a liquid as it absorbs heat. In physics, thawing occurs when heat energy raises a substance above its melting point, supplying the latent heat of fusion (ice requires about 334 kilojoules per kilogram). The rate of thawing depends on the temperature difference between the material and its surroundings, the thermal properties of the material, its moisture content, and insulation.

In natural environments, thawing refers especially to seasonal warming or longer-term warming that causes ice within soil, permafrost, or glaciers to melt. Soil thawing creates an active layer that can become wet and mobile, affect drainage, and enable microbial activity. Permafrost thaw contributes to ground subsidence, alters landscapes, and can release stored methane and carbon dioxide. Thawing rates are influenced by climate conditions, solar radiation, snow cover, and hydrology.

In food science and biology, thawing describes defrosting frozen items or tissues. Safe thawing methods include gradual refrigeration, cold-water immersion with frequent water changes, and, for some foods, microwave thawing. Proper handling minimizes microbial growth and quality loss; refreezing thawed items can degrade texture and safety, and some biological tissues require controlled thawing to preserve viability.

In other uses, thaw can denote a temporary easing of tension between parties or a period of milder weather that reduces ice and snow. Overall, thaw describes a transition from solid to liquid states driven by heat, with wide-ranging physical, ecological, and practical implications.