Understanding Heat Energy and Temperature

Heat, a form of energy, is not temperature. It's the transfer of thermal energy between substances, resulting from a temperature difference. Heat flows spontaneously from hotter to cooler objects.

Temperature measures a substance's thermal state. It reflects the average kinetic energy of particles. Unlike heat, it does not depend on the amount of material, but on how vigorously particles move.

Cold does not transfer. We perceive cold when heat leaves our body. Heat always moves from a warmer place to a cooler one, never the reverse, in a natural context.

Heat is measured in joules (J) or calories (cal). One calorie is the heat needed to raise the temperature of 1 gram of water by 1°C. The British thermal unit (BTU) is also used.

Substances heat up differently. Specific heat capacity is the amount of heat needed to raise the temperature of 1 kilogram of a substance by 1°C, explaining why water absorbs more heat than sand.

Heat transfers in three ways. Conduction occurs through direct contact, convection through fluid movement, and radiation through electromagnetic waves. Surprisingly, space's vacuum can be bridged by radiant heat transfer.

Organisms regulate body temperature through adaptations. Countercurrent heat exchange in penguins' flippers minimizes heat loss. Some desert plants have reflective surfaces to deflect radiant heat, showcasing nature's diverse thermoregulatory strategies.

At -40°C, ice can instantly turn to steam when exposed to a vacuum, skipping the liquid phase entirely.