Biology (Year 12)
What is heat transfer? Heat transfer are the mechanisms by which organisms may gain or lose heat; it depends on the temperature gradient between the internal and external environments. When there is a balance between heat gain and heat loss, the organism is said to be in heat balance; the purpose of thermoregulation. Organisms manage thermoregulation through the interaction of their physiological, structural and behavioural mechanisms. There are four mechanisms are heat loss and gain;
How do the mechanisms of heat transfer work?
Conduction refers to the transfer of heat energy from a hotter object to a cooler object by direct contact, for example, a hot plate of food is placed on a cold table, transferring the heat from the plate to the table to balance heat.
Convection transfers heat when hot air or liquid rises and is replaced by cooler air or water. Convection currents of air remove heat energy from the surface of an organism as they pass over it.
Evaporation, in relation to thermoregulation, occurs when a liquid (either water or sweat) turns to vapour, cooling the skin. Heat is transferred from the surface of the skin to the water molecules as they evaporate, and as the vapour moves off the skin and into the surroundings, the vapour containing the transferred energy carries the heat energy away from the organism.
Radiation occurs when heat is transferred from an object via infrared waves; it is the emission of electromagnetic heat waves. Heat radiates from the sun and from dry skin in the same manner.
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