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All about Energy

All about Energy. Energy – the ability to do work. Work – what is accomplished when a force was put on an object and that object was moved. Force – a push or pull that requires energy. What force are we familiar with? ________________. There are two major classes of energy:

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All about Energy

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  1. All about Energy Energy – the ability to do work. Work – what is accomplished when a force was put on an object and that object was moved. Force – a push or pull that requires energy. What force are we familiar with? ________________ • There are two major classes of energy: • Potential Energy • Kinetic Energy Potential Energy - The energy of position or stored energy. Objects that are resting have high potential energy. Objects that are cooler have high potential energy. Kinetic Energy – The energy of motion. Objects that are moving have a high kinetic energy. High temperature objects also have a high kinetic energy. Potential and Kinetic Energies are inverse. Mrs. Degl

  2. Electromagnetic Energy – energy that travels in the form of a wave The Sun gives off Electromagnetic Energy The Electromagnetic Spectrum is on page 14 in the ESRT’s… Go there Waves from the spectrum travel as a transverse wave A transverse wave is a wave that vibrates at right angles to it’s direction of travel (It goes up and down at the same time that it goes forward). Crest – the tops of waves Troughs – the bottoms of waves Amplitude – the highest points of a waves Wavelength – the distance between two adjacent crests Frequency - the # of crests passing a given point per second Mrs. Degl

  3. All objects give off electromagnetic energy. Even objects that are frozen give off EME. An object must be at ABSOLUTE ZERO (that is OK – all motion stops) in order for it to stop radiating energy. This temperature has not been reached as of yet. Let’s get out page 14 in the ESRT’s and compare the two charts. Mrs. Degl

  4. A few facts: • The Sun produces (radiates) mostly visible light • The Earth gives off (re-radiates) mostly infrared (heat) at night • Red light has the longest wavelength • Blue-Violet light has the shortest wavelength • Gamma rays have the shortest wavelengths of the electromagnetic spectrum • Radio waves have the longest wavelengths of the entire spectrum • Short waves are the most dangerous because there are more crests passing by • Long waves are the safest because there are less crests passing by Mrs. Degl

  5. Mrs. Degl

  6. Short wave (visible light) is radiated by the Sun, and taken in by the Earth. Long wave (infrared) is re-radiated by the Earth at night. The Sun produces more visible light than any other wavelength. Mrs. Degl

  7. When visible light hits the ground 4 different things can happen to it: 1. Reflected 2. Refracted 3. Scattered 4. Absorbed Reflected– light is bounced back in the same direction from which it came Refracted – light is bent as it passes through something Scattered – the energy is bounced back in many directions Absorbed– the light is taken in by the object that the light hits (the temperature will rise) Mrs. Degl

  8. INcoming SOLar radiATION Incoming Solar Radiation = Sunlight Reflection – lights reflects when it hits light colored, smooth, opaque surfaces (mirror, still water, …..) Refraction - lights refracts when it hits light colored, smooth, transparent surfaces (sunrises/sunsets, objects appear bent in water) Scattering– light scatters when it hits light colored, rough, opaque surfaces Absorbed– light is absorbed when it hits dark colored, rough, opaque surfaces (blacktop gets hotter than grass, you don’t wear black cloths in the Sun) Mrs. Degl

  9. Energy Transfer Energy can neither be created nor destroyed. It can only be transferred from one form to another. There are 3 ways to transfer energy: 1. Conduction 2. Convection 3. Radiation The transfer of energy by electromagnetic waves. This can happen in outer space (empty space) or in non-circulating air. The Sun gives us energy by radiation. The transfer of energy through circulating fluids. Fluids can be either liquids or gases. The transfer of energy by the physical contact of atoms. Only SOLIDS transfer by conduction. Mrs. Degl

  10. Energy is transferred from a source to a sink. A source is an object that gives off more heat than it takes in. A sink is an object that takes in more heat than it gives off. Any object that is a good absorber of energy is also a good radiator of energy. When two objects reach the same temperature they are at Dynamic Equilibrium (equal temperature). Temperature – the average kinetic energy of the molecules (Measured with a thermometer and expressed in degrees) Heat – the total kinetic energy of the molecules (Measured with a calorimeter and expressed in calories) Energy is always transferred at an interface. An interface is a boundary!!!!! Remember that word Mrs. Degl

  11. Specific Heat A measure of how quickly or slowly a substance changes temperature Objects with a high specific heat take a very long time to heat up or cool off. Liquid water changes temperature the slowest of all Earth materials. Objects with a low specific heat will heat up and cool off very quickly. Metals heat up and cool off very quickly because they have a low specific heat. Lead has the lowest specific heat of all common Earth materials. Mrs. Degl

  12. Latent Heat The energy needed for a substance to change phase without changing temperature. There are 3 phases of matter: 1. Solid 2. Liquid 3. Gas (Vapor) Molecules are spaced the furthest apart Molecules are closest together (Highest Density) Molecules are spaced a bit further apart (Lowest Density) (Lowest Temperature) (Highest Temperature) Remember…water is the opposite to all other Earth materials. Water is actually the most dense as a liquid (ice floats in liquid water). Mrs. Degl

  13. Phase Changes/State Changes Solid to Liquid = Melting = Fusion - Heat is being added Liquid to Vapor = Boiling = Evaporation – Vaporization – Heat is being added Solid to Vapor = Sublimation – Heat is being added Vapor to Liquid = Condensation – Heat is being removed Liquid to Solid = Freezing = Fusion – Heat is being removed Vapor to Solid = Sublimation – Heat is being removed (How snow forms) Vapors have the most stored energy because they went through two phase changes (additions of heat) in order to become a vapor. So, vapors have the most Potential Energy, and solids have the least. Mrs. Degl

  14. The temperature does not change while a substance is changing phase. • Latent Heat (stored/potential) is used during a phase change. • Notice how there is a plateau during each phase change. • Notice how the temperature increases between phase changes only. • Other liquids (not water) have the same heat curve, but they plateau (change phase) at different temperatures. Mrs. Degl

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