Energy and Energy Resources Energy • Defined as the ability to do work or the ability to cause change. Two types of energy: • Kinetic energy- energy of motion; anything that moves has kinetic energy, cars, balls, and even atoms. • Potential energy- stored energy; sometimes called energy of position, anything not moving has potential energy Swinging Pendulum P.E. is greatest here, K.E. = 0 P.E. is greatest here, K.E. = 0 Kinetic energy is greatest here, P.E. =0 Kinetic energy • The amount of kinetic energy an object has depends on two things: 1. mass 2. velocity K.E. = 1/2mv2 ½ (mass X velocity squared) Potential Energy • This is the energy that something that is not moving has the potential of having. • Potential energy depends on: 1. mass 2. position (height and gravity) P.E. = mgh (mass X gravity X height) Forms of energy • • • • • • Thermal Chemical Light Sound Electrical Nuclear All forms of energy have kinetic and/or potential energy. Thermal energy • Heat energy- all objects have thermal energy; it increases as temperature increases. Which has more thermal energy? Why? Chemical Energy • Energy stored in chemical bonds; includes the food we eat. Light energy • Form of energy that we see. Sound energy • Energy caused by vibrations; some of these vibrations we can hear. Electrical energy • Energy that is carried by an electric current (a path that electrons follow). Nuclear Energy • Energy from the nucleus of an atom Energy Transformations • Change from one form of energy to another. • Always produces thermal energy (heat). Examples of energy transformations • Photosynthesis (light to chemical) • Digestion of food (chemical to mechanical) • Burning of fuel (chemical to mechanical and thermal) • Electrical to light and thermal (light bulb) Law of Conservation of Energy • States that energy cannot be created or destroyed, only transferred or changed from one form to another. Kinetic and Potential Energy Kinetic energy and potential energy can be transferred back and forth as seen in a swinging pendulum or throwing a ball up. Transforming Chemical Energy • Can be seen as chemical reactions occur in living things causing bonds to be broken and kinetic energy (contraction of a muscle) to be formed. • Decomposition of dead or decaying matter. Transforming Electrical Energy • Electrical energy can be transformed to sound energy (listening to the radio) • Electrical energy can be transformed to chemical energy (neurons “fire” and release chemicals) Transforming Thermal Energy • Thermal energy can be changed to mechanical energy (steam used to move locomotives) • Thermal energy can be transformed to light (radiant) energy (glowing metal on stove) Generating Electrical Energy • Generator- device that transforms kinetic energy into electrical energy • Turbines- set of steam powered fan blades that spins a generator at a power plant. Electric Power Plants Power plants- most power plants use energy from coal to start the transformation of energy similar to below. Chemical Energy of Coal Thermal Energy of Water Kinetic energy Of turbine Kinetic Energy of Steam Electrical Energy Sources of Energy Energy that we use comes from two main sources: 1. Renewable resources- resources that can be replaced 2. Nonrenewable resources- resources that cannot be replaced Nonrenewable Resources • Fossil Fuels- formed from the remains of once living things. - energy from these can be traced back to the sun through the food chain Fossil Fuels- there are three main types of fossil fuels • Coal- formed from the remains of plants that once lived on land • Petroleum-(crude oil) formed from the remains of microscopic organisms in the oceans. • Natural gas- sometimes found along with deposits of petroleum; also formed from ancient ocean microscopic life Coal • Primarily used for generating electricity; also used for paper production and iron and steel production. • Coal is mined from deposits in two methods: Surface mining Underground minin Petroleum • Refining petroleum produces gasoline, kerosene, asphalt and petrochemical products such as plastics; some perfumes and insecticides are made from products of crude oil Natural gas (methane) • Natural gas is used to heat ( and in some cases cool) homes and other buildings; also used for generating electricity • Burns the cleanest of the fossil fuels • Can be produced- (by-product of decaying organic matter) What’s so bad about these fossil fuels? 1. Energy crisis – result of over dependence on fossil fuels 2. Burning fossil fuels releases sulfur dioxide which mixes with rain and causes acid rain 3. Burning fossil fuels also releases carbon dioxide which contributes to the greenhouse effect Nuclear energy • Energy from fission (splitting of the atom) can be converted to other sources of energy such as electricity • Negatives- produces radiation that has to be contained; Uranium is nonrenewable Renewable Resources • • • • • • Solar energy Geothermal energy Tidal energy Wind energy Hydroelectric energy Biomass Solar energy- energy from the sun • Collected by thermal collectors (roofs) or photovoltaic cells (calculators, roofs, satellites) Geothermal energy- heat from deep inside the earth is used as an energy source Wind energy- windmills convert kinetic energy to electrical energy Hydroelectric energy • Water that is behind a dam can be used to move turbines and generate electricity. Tidal energy • Energy from the ocean tides can be used to generate electricity. Biomass • Energy from living things (primarily plants) can be used for fuel.