Chapter 5Energy

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.