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10/5/2016 What is energy? Energy is the ability of a system to do work or supply heat. Forms of energy Light Energy is NOT matter because it does not take up space nor does it have mass Heat Sound https://vimeo.com/123271598 Electricity Energy Types 1. Potential: energy due to its distance from other objects (stored energy) Types of KE Motion Thermal Energy Sound Energy Electromagnetic Radiation Electric Energy 2.Kinetic: energy of motion Kinetic Energy as Motion Kinetic Energy as Thermal Energy Airplane flying or meteor plummeting Thermal energy is directly related to TEMPERATURE. Related to the mass of the object and its velocity. We can’t see individual atoms vibrating, but we can feel their kinetic energies as temperature. 1 10/5/2016 TEMPERATURE- is a measure of the average KE of the particles. A MEASURE OF THE AVERAGE KE OF THE PARTICLES! Kinetic Energy as Sound Energy Sound waves are made when stuff vibrates– like strings on an instrument or gas molecules in the air. Sound waves travel when the vibrating stuff causes stuff surrounding it to also vibrate. Sound doesn’t travel in a vacuum, because a vacuum has no atoms to transmit the vibration. Electromagnetic Radiation- KE Electric Energy Electromagnetic Energy is the same as radiation or light. This type of energy can take the form of visible light, UV radiation, radio waves, or Xrays. Electric energy is the kinetic energy of moving electrons, the negativelycharged particles in atoms. Physicists describe electromagnetic radiation as being composed of PHOTON (tiny packets of energy). Each photon has a particular amount of energy. Types of PE Chemical Potential Energy Electricity is the KE of flowing electrons between atoms. Chemical Potential Energy Chemical energy is stored in the bonds between atoms in compounds. This stored energy is transformed when bonds are broken or formed through chemical reactions. Nuclear Potential Energy Gravitational Potential Energy Mechanical (Elastic) Potential Energy 2 10/5/2016 Nuclear Potential energy Gravitational Potential Energy Systems can increase gravitational energy as a mass moves away from the center of the Earth or other objects that are large enough to generate significant gravity (our sun, the planets and stars) Today’s nuclear power plants are fueled by fission. Uranium or plutonium atoms are broken apart, freeing lots of energy. Hydrogen atoms in the sun experience nuclear fusion, combining to form helium and subsequently releasing large amounts of energy in the form of electromagnetic radiation and thermal energy. Most atoms are stable on Earth; they keep their identifies as particular elements. Nuclear reactions change the fundamental identify of elements by changing the nuclei of the atoms. Mechanical (Elastic) Potential Energy Elastic energy can be stored mechanically in a compressed gas or liquid, a coiled spring, or a stretched elastic band. On an atomic scale, the stored energy is a temporary strain placed on the bonds between atoms, meaning there’s no permanent change to the material. These bonds absorb energy as they are stressed, and release the energy as they relax. Power plants transform chemical potential energy in fossil fuels to electricity. Energy can shift forms, but is never created or destroyed! A car transforms the PE trapped in gasoline into various types of energy that move the car. Most is converted to thermal energy (heat). Nuclear Power plants change the nuclear potential energy of uranium or plutonium into electricity too. An efficient fossil fuel plant loses more than half of the energy it creates to forms other than electricity, such as heat, light, or sound 3 10/5/2016 Wind turbines change the KE of air molecules in wind into electricity. Hydroelectric power plants take advantage of gravitational potential energy of water as it falls from the top of a dam to the bottom. On the Arizona-Nevada border to tame the Colorado River and provide water and hydroelectric power for the developing Southwest. http://www.history.com/topics/ hoover-dam (5 mins) Laws of Conservation Example: Chemical energy transferred into and = light energy Energy: • Energy is neither created nor destroyed • The amount is TRANSFERRED!! Example: Heat absorbed by cold pack = Heat lost by surroundings Hungary Dragon Demo Energy in Reactions Exothermic: gives off energy (heat, light) + Signs of a change from chemical potential energy to other forms of energy. = (The surroundings feel HOT) https://youtu.be/18sifodnVDo Endothermic: absorb energy (cold) (The surroundings feel COLD) 4 10/5/2016 Temperature vs. Heat (MOTION) Temperature: measures average kinetic energy of particles Cup of water and a bathtub of water are both at 30° C. WHICH HAS MORE HEAT ENERGY? Heat: sum total of kinetic energy of the particles (ENERGY!!) The bathtub because it has more mass!!! Temperature Scales °C = K – 273 Absolute Zero = 0 K = - 273 °C 1) °C = ?, K = 300 Kelvin (K) Water freezes at 273 K Water boils at 373 K 2) °C = ?, K = 401 Celsius (°C) Water freezes at 0 °C Water boils at 100 °C 3) K = ?, °C = -26 °C = 27 °C = 128 K = 247 °C = K – 273 Laws of Conservation Mass: • mass is neither created nor destroyed in chemical reaction. (THE ATOMS ARE MERELY REARRANGED>) • Start with 50.0 grams, End with same! + 25.0 g + = 25.0 g = 50.0 g 5