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THERMAL ENERGY

THERMAL ENERGY. THERMAL EQUILIBRIUM. Moves heat energy from warmer to cooler regions Example, water/antifreeze in a radiator. HEAT Form of energy found in the vibrating motion of atoms and molecules. TEMPERATURE Measurement of heat energy Scalar quantity Fahrenheit ( 0 F) Celsius ( 0 C)

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THERMAL ENERGY

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  1. THERMAL ENERGY

  2. THERMAL EQUILIBRIUM • Moves heat energy from warmer to cooler regions • Example, water/antifreeze in a radiator

  3. HEAT Form of energy found in the vibrating motion of atoms and molecules TEMPERATURE Measurement of heat energy Scalar quantity Fahrenheit (0F) Celsius (0C) Kelvin (K) HEAT VS. TEMPERATURE

  4. Heat increases the KE of the substance • The substance expands especially gases • Work may be done • Examples- rubber band, steeel balls

  5. Total Energy is conserved • D PE + D KE + D U = 0

  6. WHY DOES HEAT FLOW FROM HOT- TO- COLD? • Heat gives added energy to molecules which move faster and then the energy is passed on to surrounding cooler molecules

  7. HOW DOES A THERMOMETER WORK? • When temperature in a mercury or colored alcohol glass tube increases, the liquid expands and rises up the tube

  8. TEMPERATURE SCALES • Scale Boiling Pt. Freezing Pt. • Fahrenheit 2120F 320F • Celsius 1000C 00C • Kelvin 373K 273K

  9. CONVERSIONS • 0C = 5/9 ( 0F - 320) • 0F = 9/5 0C + 320 • K = 0C + 273 • 0C = K - 273

  10. SOLVE THIS PROBLEM • An electric motor is operating at a temperature of 1150F. It is located in a workshop where the room temperature is 750F. • Find the room temperature in 0C. • Find the room temperature in K.

  11. ROOM TEMPERATURE IN 0C • 0C = 5/9 ( 75-32) • 0C = 5/9 ( 43 ) • 0C = 23.9 = 240C

  12. ROOM TEMPERATURE TO K • K = 0C + 273 • K = 24 + 273 = 297K

  13. Conduction, Convection, Radiation • Conduction- The transfer of energy through matter in which energy moves from particle to particle ---touching; more easily in solids than liquids or gases • Convection-The transfer of energy by the bulk movement of matter in which particles move from place to place in a fluid---often movement of heat in air • Radiation- The transfer of energy in the form of waves—often from the SUN

  14. Conductors & Insulators • Thermal conductors-substances that rapidly transfer heat energy • Insulators reduces heat loss by slow transfer of heat energy

  15. Specific Heat Capacity • The quantity of heat required to raise the temperature of 1 kg of a substance by 10 C at constant pressure • The specific heat of water is 4.18 J / g . 0C

  16. Q = m c DT • Q = heat measured in J • c = specific heat capacity in J/kg.0C • m = mass in kg • DT = temperature in 0C • Example- food lab

  17. Phase Change • Melting or solidification • Latent heat – energy per unit mass that is transferred during a phase change of a substance • Can be heat of fusion or heat of vaporization

  18. Heat of fusion- energy transferred to change from solid to liquid or liquid to solid • Heat of vaporization- energy transferred to change from liquid to vapor or vapor to liquid • Vaporizing or condensing

  19. Phase Change graph

  20. Laws of Thermodynamics • 1st Law – The total change in internal energy from its initial to final equilibrium conditions is equal to the transfer of energy as both heat and work.

  21. 2nd Law- No machine can transfer all of its absorbed energy as work • This can be explained as entropy- a measure of the disorder of a system, natural processes increase entropy • Increasing disorder means there is less energy to do work

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