A form of energy that is always transferred from a warmer substance to a cooler one.

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The form of energy that is always transferred from a warmer substance to a cooler one is known as heat. Heat can be transferred through three methods: conduction, convection, and radiation.

1. Conduction: This is the transfer of heat through direct contact between particles of different temperatures. When two substances with different temperatures come into contact, the particles in the warmer substance transfer their heat energy to the particles in the cooler substance, resulting in temperature equalization. For example, when you touch a hot stove, heat is conducted from the stove to your hand.

2. Convection: This is the transfer of heat through the movement of fluid (liquid or gas). When a warmer substance heats up a fluid, the heated fluid becomes less dense and rises, while the cooler fluid descends. This creates a cyclic flow that transfers heat between the warmer and cooler regions. An example of convection is the circulation of warm air in a room when a heater is turned on.

3. Radiation: This is the transfer of heat through electromagnetic waves. Unlike conduction and convection, which require a medium (solid, liquid, or gas), radiation can occur in a vacuum. Heat energy is emitted from a warmer object in the form of electromagnetic waves, which can travel through space and be absorbed by cooler objects. This is how the Sun's heat reaches us on Earth.

So, to summarize, heat is the form of energy that always flows from a warmer substance to a cooler substance. It can be transferred through conduction, convection, and radiation.