Energy is defined as the capacity to do work or to produce heat. The law of conservation of energy states that energy can be converted from one form to another, but can never be created or destroyed. This principle is also known as the the first law of thermodynamics. Energy can be classified in two major categories--potential or kinetic. Potential energy is energy as a result of an object's position or composition. The kinetic energy of an object is due to motion of the object and depends on the mass and velocity of the object. The following equation determines the kinetic energy of an object, when given its mass and velocity:
Heat and temperature are two different things. Temperature is a measurement that reflects the motions of particles within a substance. Heat is a transfer of energy between two objects with a different temperature.
When a chemical reaction occurs and heat is evolved, it is called an exothermic reaction. For example, the burning of gas is the exothermic reaction, which is why it is used for heating homes. Reactions that absorb energy from their surroundings often result in the lowering of temperature, and are known as endothermic reactions.
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Unit 5 - Section 2