P210 12a


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P210 12a

  1. 1. Temperature
  2. 2. Microscopic Atoms Atoms in matter are in constant motion. Interaction of atoms determines the state of matter. Solid  Liquid  Gas • Atoms vibrate • Atoms close, • Atoms apart, in a nearly but free to freely moving in fixed position move around the volume
  3. 3. Macroscopic Properties There are about 5 x 1024 Microscopic properties: atoms in a golf ball. We track its motion as a mass, position, velocity, energy whole, not as atoms. Density and pressure apply Macroscopic properties: to the whole object, not the atoms. mass, position, velocity, energy These are macroscopic and properties. density, pressure, temperature
  4. 4. Hot and Cold Temperature is a macroscopic property of matter. • Based on statistics • Doesn’t generally apply to single atoms Hot matter has more energy per atom on average than cold matter. • Single atoms may have less energy in a hot item
  5. 5. Thermal Contactheater  Two cups of water are in contact. • Heat one cup • Compare macroscopic properties  If they are the same they areheater in thermal contact. • eg. metal cups  If different they are insulated.
  6. 6. Thermal Equilibrium Two systems have the same temperature if they are in thermal equilibrium. • Equilibrium between systems • Measure of macroscopic properties If two systems are not in thermodynamic equilibrium, they are not in thermal contact.
  7. 7. Law Zero If two systems are each in thermodynamic equilibrium with a third system, then they are in thermodynamic equilibrium with each other. This is the Zeroth Law of Thermodynamics. A is in thermal equilibrium with B. A B C C is in thermal equilibrium with B. Therefore, A is in thermal equilibrium with C.
  8. 8. Gas Thermometer A system with known macroscopic properties may be placed in thermodynamic equilibrium. A device that uses this is a thermometer. This thermometer uses the pressure of gas in a bulb. The meter measures the height in a manometer or barometer.
  9. 9. Kelvin Temperature requires a 10-4 K Superfluid liquid helium scale to compare different 4K Helium boils systems. 77 K Air boils The Kelvin (K) is the SI unit 273 K Water melts of temperature. 373 K Water boils • Based on behavior of water • Linear pressure scale 630 K Mercury boils • Not degrees Kelvin 1000 K Copper melts 6000 K Surface of the sun P 106 K Solar corona T = 273.16 P3 108 K Hydrogen bomb
  10. 10. Temperature Scales For everyday temperatures  The English system uses the the Celsius scale (°C) is Fahrenheit scale (°F). used.  Ice point at 1 atm is 32°. Each °C is the same  Boiling point at 1 atm is magnitude as 1 K. 212°. • The zero is different  Each °F is 5/9 of a °C. • 0 °C = 273.15 K • Not quite T at P3 9 TF = TC + 32 5
  11. 11. Body Temperature Normal body temperature is  The general formula applies 98.6 °F. What is the for a conversion between equivalent in °C and K? scales. • TC = (5/9)(TF – 32) If your fever is 101.6 °F, by • (5/9)(98.6 – 32.0) = 37.0 °C how much has it risen in °C • T = TC + 273.15 = 310.2 K and K?  The difference use the fractional change. • ∆TC = (5/9) ∆TF • (5/9)(101.6 – 98.6) = 1.7 °C • ∆T = ∆TC = 1.7 K next