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Nature of Energy

Nature of Energy. Energy is all around you! You can hear energy as sound. You can see energy as light. You can feel it as wind and heat. You use energy when you: hit a softball. lift your book bag. compress a spring. Burn fuel. States of Energy: Kinetic and Potential Energy.

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Nature of Energy

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  1. Nature of Energy • Energy is all around you! • You can hear energy as sound. • You can see energy as light. • You can feel it as wind and heat. • You use energy when you: • hit a softball. • lift your book bag. • compress a spring. • Burn fuel

  2. States of Energy: Kinetic and Potential Energy • Kinetic Energy is the energy of motion. • Potential Energy is stored energy of position or chemical bonds.

  3. Nature of Energy • Energy is involved when: • a bird flies. • a bomb explodes. • rain falls from the sky. • electricity flows in a wire.

  4. Kinetic Energy • The energy of motion is called kinetic energy. • The faster an object moves, the more kinetic energy it has. • The greater the mass of a moving object, the more kinetic energy it has. • Kinetic energy depends on both mass and velocity.

  5. Kinetic Energy K.E. = ½ mass x velocity2 What has a greater affect of kinetic energy, mass or velocity? Why?

  6. Potential Energy • Potential Energy is stored energy. • Stored chemically in bonds of fuel or food • Stored as nuclear energy holding subatomic particles together • Or stored because of the work done on it: • Stretching a rubber band. • Winding a watch. • Pulling an arrow back on a bow’s string. • Lifting a brick high in the air.

  7. Gravitational Potential Energy • Potential energy dependent on height is called Gravitational Potential Energy (a form of mechanical energy)

  8. Gravitational Potential Energy • If you stand on a 3-meter diving board, you have 3 times the G.P.E, than you had on a 1-meter diving board. • GPE=Weight x Height • (pounds) x (feet) • or (Newtons) x (meters) • GPE = (M)(Ag) (H) • M=Kg, Ag =9.8m/sec2,H=m

  9. Kinetic – Potential Energy Conversion Cars are mechanically pulled to the peak which is the point of maximum potential energy, the car has minimum kinetic energy. As position is exchanged for speed, potential is converted to kinetic energy.

  10. Ball speeds up Ball slows down

  11. Forms of Energy • The five main forms of energy are: • Heat • Chemical • Electromagnetic • Nuclear • Mechanical

  12. Heat Energy • The internal motion of the atoms is called heat energy, because moving particles produce heat. • Heat energy can be produced by friction. • Heat energy causes changes in temperature and phase of any form of matter.

  13. Chemical Energy • Chemical Energy is required to bond atoms together. • And when bonds are broken, energy can be released or absorbed • Exothermic = energy released. • Endothermic=energy absorbed.

  14. Chemical Energy • Fossil Fuels and our Food are forms of energy stored in chemical bonds • The Energy came from nuclear fusion on our Sun and was photosynthesized by plants and stored in plant and animal life

  15. Formation of Fossil Fuels • Petroleum and Natural gas are both products of millions of years of decomposing Marine life, both animal and plant • Coal is similar but mostly from terrestrial plant life

  16. Where does Coal come from?

  17. Electromagnetic Energy • Electricity -- carried in wires • Light -- Each of the colors of light (ROY G BIV) represents a different amount of electromagnetic energy • X-rays & Cosmic Rays • TV & Radio waves • Laser light.

  18. Nuclear Energy • When the nucleus splits (Fission), nuclear energy is released in the form of heat energy and light energy. • Nuclear energy is also released when nuclei collide at high speeds and join (Fusion). • MOST CONCENTRATED

  19. Mechanical Energy • When work is done to an object, it acquires energy. The energy it acquires is known as mechanical energy.

  20. Mechanical Energy • When you kick a football, you give mechanical energy to the football to make it move.

  21. Energy Conversion • Energy can be changed from one form to another. Changes in the form of energy are called energy conversions. • Good Examples on Pages 418-419

  22. Energy conversions • All forms of energy can be converted into other forms. • The sun’s energy through solar cells can be converted directly into electricity(Photovoltaic energy). • Green plants convert the sun’s energy (electromagnetic) into the bonds in starches and sugars (chemical energy) using Photosynthesis.

  23. Other energy conversions • In an electric motor, electromagnetic energy is converted to mechanical energy. • In a battery, chemical energy is converted into electromagnetic energy. • Mechanical energy of water falling can be converted to electrical energy in a generator.

  24. Hydroelectric Power

  25. Forms of Alternative Energy

  26. Energy Conversions • In an automobile engine, fuel is burned to convert chemical energy into heat energy. The heat energy is then changed into mechanical energy.

  27. Chemical  Heat Mechanical

  28. The Law of Conservation of Energy • Man can neither create nor destroy Energy by ordinary means. • It can only be converted from one form to another. • If energy seems to disappear, then scientists look for it – leading to many important discoveries.

  29. Law of Conservation of Energy • In 1905, Albert Einstein said that mass and energy can be converted into each other. • He showed that if matter is destroyed, energy is created, and if energy is destroyed, mass is created. • E=MC2 • M=mass C=speed of light

  30. Power = measure of Energy • Work = Force x Distance • Rate of doing Work or • Amount of Work/unit of time • Power= Work/Time • Power = (Force x Distance)/Time • Power Units = Watts • 1Watt=1Joule/sec or (1N*m/sec) • 1 Kilowatt = 1000 watts • 1 Horsepower = 746 watts

  31. Thermal Energy (Heat) differs from Temperature

  32. Heat vs. Temperature • Heat content is the TOTAL KINETIC ENERGY of the particles in a sample • Temperature is the AVERAGE KINETIC ENERGY of the particles in a sample

  33. Which has more Heat and which has the highest temperature?

  34. Insulators • There are thousands of air bubbles trapped in the styrofoam which slows down the heat flow through the layer

  35. Insulation: How do the Polar Bears stay warm in the snow? Their dense, fine fir traps an air layer next to their skin.

  36. Home Insulation • The pink fiberglass fibers trap air in the mat of insulation preventing heat from escaping in the winter or heat from entering during the summer. Insulation

  37. Highly Insulating Windows • Two or three panes between inside and outside air • Insulation is supplied by the Dead Air Space Image source: Southwall Technologies

  38. Heat Transfer • Occurs three ways • Conduction • Convection • Radiation

  39. Conduction • The transfer of heat by direct contact between objects or particles. • Motion of solid atoms or molecules carried from particle to particle

  40. Convection • Heat transferred by the movement of molecules within liquid or gaseous substance. • Warm rises, cool sinks. • A circular motion begins from warmer areas rising due to decreased density moving toward cooler areas which fall because of increased density. • Wind and Major Weather patterns are caused and move largely because of these convection currents.

  41. Radiation • Heat transferred through space • MATTERis not neededfor radiation • EXAMPLE: The sun’s rays carrying visible light and UV light causing sunburn.

  42. Radiation • Transfer of heat through electromagnetic radiation (light from stars or light bulbs). • Transferred in all directions. • Matter is not required! • Dark or dull objects absorb more than light or shiny objects do.

  43. Temperature • Temperature is ameasure of the average KE of the particles in a sample of matter

  44. Temperature Conversions • oC to oF: oF = (9/5)oC + 32 • oF to oC: oC = 5/9(oF – 32) • oC to K: K = oC + 273 • K to oC:. oC = K – 273

  45. Going from Celsius to Fahrenheit Convert 37 oC to oF. oF = (9/5)oC + 32 oF = (9/5)37oC + 32 = 66.6 + 32 = 98.6oF

  46. Going from Fahrenheit to Celsius Convert 68oF to oC oC = 5/9(oF – 32) oC = 5/9(68 – 32) = 5/9(36) = 20 oC

  47. Going from Kelvin to Celsius Convert 310 K to oC oC = K – 273 oC = 310 – 273 = 37oC

  48. Thermal Energy 80ºC 80ºC 400 mL A B 200 mL • Which beaker of water has more thermal energy? • B - same temperature but more mass

  49. Thermal energy relationships a. As temperature increases, so does thermal energy (because the kinetic energy of the particles increased). b. Even if the temperature doesn’t change, the thermal energy in a more massive substance is higher (because it is a total measure of energy). c. Energy always travels from a high concentration(warm) to a lower concentration(cool) of heat.

  50. Land heats up and cools down faster than water. The temperature of the water helps keep the land temperature stable.

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