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# Energy

Introduction: Energy exists all around us, in various forms. Fire, for example, involves the transfer of thermal energy. Energy refers to the ability to do work or to transfer heat. Work refers to a force acting over a specific distance, while heat refers to the transfer of energy between two objects due to differences in temperature. The two primary types of energy are kinetic energy - which deals with the energy of motion - and potential energy - which deals with stored energy that is often associated with height. The total of the potential and kinetic energies in an object is known as mechanical energy.

Energy generally carries no mass and no charge, so it cannot be classified as matter. Energy is typically measured in joules, though it can also be measured in calories. It is worth knowing that the calories used to measure energy differs from the "Calories" used in food, as the "Calories" in food actually refer to kilocalories. Much of thermochemistry concerns itself with a discussion of thermal energy, which refers to the energy of the random motion of particles in a sample of air. Also studied in thermochemistry is temperature, which measures the average kinetic energy of an object. Heat and temperature differ in that heat focuses on the total amount of energy in an object, while temperature depends on the average kinetic energy of each particle. So, an object with greater mass may have more thermal energy than a smaller-mass object, even though their temperatures can still be the same.

An understanding of temperature and heat is essential when studying the different ways in which energy can affect particles. As temperature increases, the average kinetic energy and the motion of particles will increase. Heating an object will increase temperature, while cooling an object will decrease temperature. Heat, in the context of chemistry, involves a transfer of energy in one of three ways: conduction, convection, and radiation. Conduction involves the transfer of energy between two objects in direct contact. Convection involves the transfer of energy between an object and its surroundings, due to motion in a fluid. Radiation involves the transfer of energy through electromagnetic radiation. All three methods of heat transfer can be witnessed in everyday life. Conduction is seen when a poker becomes red hot after being in direct contact with flames. Convection is seen as water is heated in a pan. Radiation is seen when the Sun provides heat via electromagnetic radiation on a warm beach.

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