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Chapter 12: Energy and Energy Resources Carin Miranda 6-1 2007 What is Energy? • Energy is the ability to do work. • Work and energy are both expressed in joules (J). Kinetic Energy • Kinetic energy is the energy of motion. • All moving objects have kinetic energy. • Kinetic energy= mass times speed squared divided by 2. • The faster something is moving, the more kinetic energy it has. • The more massive the object the more kinetic energy it has. Potential Energy • Potential energy is energy based on shape or position. • Gravitational potential energy is based on height and weight. • The higher an object the more potential energy. • The more massive an object the greater the potential energy. Mechanical Energy • Mechanical energy is the total energy of motion and position. • In other words it is kinetic plus potential. • As potential goes up kinetic goes down and vice versa. Forms of energy • • • • • • Thermal (Heat) Chemical Electrical Sound Light Nuclear Thermal • Higher temperature objects have more thermal energy and more kinetic energy. • The particles in steam move faster than the particles in ice. • The more particles the more thermal energy. • A bathtub full of 75 degree water would have more thermal energy than a cup full of 75 degree water. Chemical Energy • When particles are broken down and cannot return to their original form they have chemical energy. • Examples: Food, Charcoal, gasoline, firewood. Electrical Energy • Moving electrons. • Any electrical appliances or anything using electricity. • Huge magnets are rotated to produce the electricity you use at home. Sound Energy • Caused by an objects vibrations. • It is a form of potential and kinetic energy. Light Energy • Vibrations of electrically charged particles. • Not all light energy is seen. • Microwaves use light energy. Nuclear Energy • Two or more nuclei join together (nuclear fusion). Example: Sun • Nucleus of an atom splits apart (nuclear fission). Example: Uranium atoms split apart to produce electricity. Energy Conversions •Any change from one form of energy to another. Kinetic to Potential • Remember we said as potential energy goes up kinetic goes down and vice versa. • Examples: Person on a trampoline, pendulum, and wind up toys. Chemical Energy Conversions • Chemical energy in food is converted into kinetic energy when you move. • It is stored as potential energy when you aren’t moving. • Where did that chemical energy come from in food? • The sun gives plants light energy and they convert it into chemical energy. • Batteries are another example of chemical energy. Electrical Energy Conversions • Lots of examples: • Alarm clock: electrical to light and sound. • Battery: chemical to electrical • Light bulb: electrical to light, thermal, and sometimes sound. • Blender: electrical to kinetic and sound Energy and Machines • Machines make work easier by changing the size and/or direction of the force required to do the work. Why Conversions are Important •Make energy useful. •Make conversions more efficient. Conservation of Energy • Friction is a force that opposes motion between two surfaces that are touching. • When energy is used to overcome friction some energy is converted into thermal energy. • On a roller coaster potential energy is greatest at the top of the biggest hill and kinetic energy is greatest at the bottom of the biggest hill. Law of Conservation of Energy • Energy can be neither created nor destroyed. • It can change from one form to another. • Every time an energy conversion takes place some energy is always converted into thermal energy. Energy Resources • A natural resource that can be converted by humans into another form of energy to do useful work. • Can be nonrenewable or renewable. Nonrenewable • Cannot be replaced easily. • Fossil Fuels: Formed from the buried remains of plants and animals that lived millions of years ago. • Coal, petroleum, and natural gas. • Electrical energy from fossil fuels. • Nuclear Energy (Uranium pellets). Renewable • Can be replaced over a relatively short period of time. • Solar Energy (SUN). • Energy from water (Hydroelectric). • Wind Energy. • Geothermal (Hot water in the ground). • Biomass (garbage). Advantages and Disadvantages of Nuclear Energy • Advantages: very concentrated form of energy and nuclear power plants don’t produce smog (CO2). • Disadvantages: Produces radioactive waste and it is nonrenewable.