energy transfer

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Movement of energy from one place to another or from one substance to another, or the conversion of energy from one form to another. For example, in a car engine, the chemical energy of the fuel is converted to kinetic (motion), heat, and sound energy.

Chemical energy transfer
In a chemical reaction, energy is transferred between reactants and products, and between the reactants or products and their surroundings. The energy released or absorbed during the chemical reaction is the energy of reaction, or energy of formation. During a chemical reaction the amount of chemical energy stored is equal to the amount of chemical energy released; this principle is known as the law of conservation of energy. It means that energy cannot be created or destroyed, but can change from one form to another such as chemical energy changing into heat energy.

The living world
Life processes of all kinds involve energy transfer; there can be no life without it. Energy may be transferred between an organism and its surroundings, for example when heat is lost or gained. Energy is also transferred inside an organism's body. Energy is used by organisms to do things such as growing and moving.

Nearly all life on Earth depends on energy transferred from the Sun. Plants carry out photosynthesis in which the green chemical chlorophyll absorbs sunlight, the energy of sunlight being transferred to the plant. The plant uses this energy to make glucose, which is used as a fuel during respiration and is also used for growth. When animals eat plants, energy is transferred from the plants to the animals. Chemicals in the plant are absorbed by the animal, and these can then be used as fuel to provide energy for the animal. The same energy transfer occurs when animals eat other animals. So energy transfer is a key part of a food chain or a food web.

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