1. Ch. 3 Energy

2. Energy is the ability to do work or effect change. Energy can be measured in joules, J. Many different forms of energy exist: Electrical energy Thermal energy Chemical energy Wind energy Sound energy

3. Just as there is a law of conservation of matter, there is also a law of conservation of energy. Energy cannot be destroyed or created. Energy can be transferred from one substance to another. (ex. from hot water to ceramic cup) Energy can also be transformed from one type into another. (ex. electrical energy into light energy)

4. Sometimes, during a transfer or transformation of energy, some of the energy is lost. We can calculate the efficiency of a machine using: % Efficiency = amount of energy used x 100 amount of energy consumed

5. Example: Calculate the efficiency of a light bulb that gives off 20 J of energy, but consumes 32 J of electrical energy.

6. Thermal Energy: The amount of thermal energy is also known as heat energy. The quantity of heat energy in a substance is determined by its mass, specific heat capacity and its temperature.

7. Example: Which of the following contains more heat energy? Explain your choice. (a.) A 500 mL bottle of water at 18 o C. (b.) A 10 000 L swimming pool at 18 o C. HW. Textbook p. 99 # 1-6 Workbook: p. 39 ALL, p.40 #1-4