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Chapter 5 Energy Energy and Work • • • • Energy – the ability to cause change. Kinetic energy – energy in the form of motion. Potential energy – stored energy. Work – the transfer of energy through motion. – Work = Force x Distance – W = FD – Units = Joules (Newtons x meters) Conservation of Energy • Mechanical energy – the total amount of kinetic and potential energy in a system. • Law of conservation of energy – states that energy can change form but it cannot be created or destroyed under ordinary conditions. Human Energy • Calorie – a unit used by nutritionists to measure how much energy we get from specific foods. – 1 calorie ( = 1 kilocalorie) – 4180 Joules. – Each gram of fat supplies 9 calories of energy. Temperature and Heat • Temperature – a measure of the average kinetic energy of the particles in a sample of matter. • Thermal energy – is the total energy of the particles in a material. • Heat – the thermal (or internal) energy that flows from something with a higher temperature to something with a lower temperature. (i.e. heat is energy transferred between objects at different temperatures. Thermal Pollution • Thermal pollution – when waste heat significantly changes the temperature of the environment. Measuring Thermal Energy • Specific heat – amount of energy it takes to raise the temperature of 1kg of a substance by 1o C. • Thermal Energy Equation – – – – – Q = mc∆T Q is change in thermal energy m is mass c is specific heat ∆ is the final temp. – the initial temp.