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All About Energy 8th Grade Physical Science What is energy? • The ability to do work • The ability to cause matter to move • The ability to cause matter to change Measured in joules & calories Energy exists in 2 states: •Potential •Kinetic Law of Conservation of Energy • The amount of energy used to initiate a change is the same as the amount of energy detected at the end of the change. • In other words, energy cannot be created or destroyed in a physical or chemical change. Energy has several forms: • • • • • • • Light (light, electromagnetic) Nuclear (atomic) Electrical Heat (thermal) Sound Chemical Mechanical What is Potential Energy? • Stored energy • Energy of position • The amount of usable energy in a body at rest Sometimes called GRAVITATIONAL POTENTIAL ENERGY 8 Forms of potential energy 9 Gravitational Potential Energy • GPE is the energy stored in an object as the result of its vertical position (i.e., height). • Amt. of GPE is dependent on two variables: 1.the mass 2.the height 11 Elastic Potential • Elastic PE is the energy stored in elastic materials as the result of their stretching or compressing. Potential energy can be increased by: • Increasing height • Increasing mass What is Chemical Energy? • Chemical Energy is the energy of a chemical compound that changes as its atoms are rearranged. • Chemical energy is a form of potential energy because it depends on the position and arrangement of the atoms in a compound. • The energy in food is chemical energy. What is Nuclear Energy? • Nuclear Energy is energy that comes from changes in the nucleus of an atom. Nuclear energy can be produced when nuclei are joined in a fusion reaction or when a nucleus is split apart in a fission reaction. What is Kinetic Energy? • The energy of motion, or the energy an object has because it is moving Kinetic Energy can be increased by: • Increasing mass • Increasing speed 5 Kinetic Energy • Motion • KE of an object depends upon 2 variables: 1. the mass (m) of the object 2.the speed (v) of the object. 6 Calculating Kinetic Energy A formula to find the kinetic energy of any body based on its velocity. What is Thermal Energy? • Thermal Energy is all of the kinetic energy due to random motion of the particles that make up an object. • All matter is made up of moving particles, so all matter has thermal energy. • Thermal energy increases as temperature increases. • Thermal energy is always present when an enery conversion occurs!!! What is Sound Energy? • Sound Energy is caused by an object’s vibrations. The object’s vibrations transmit some kinetic energy to the air particles, which also vibrate. These vibrations transmit sound energy. What is Electrical Energy? • Electrical Energy is the energy of moving electrons. Electrical energy can be thought of as potential energy that is used when you plug in an electrical appliance and use it. What is Light Energy? • Light Energy is produced by the vibrations of electrically charged particles. • Also called electromagnetic energy Mechanical Energy • Mechanical energy is the total energy of motion and position of an object. Both kinetic energy and potential energy are kinds of mechanical energy. • ME is the sum of the KE and forms PE associated with a system • Therefore, ME= KE + PE