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Temperature

Temperature. Solid Atoms vibrate in a nearly fixed position. Gas Atoms apart, freely moving in the volume. Microscopic Atoms. Atoms in matter are in constant motion. Interaction of atoms determines the state of matter. Liquid Atoms close, but free to move around. Macroscopic Properties.

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Temperature

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  1. Temperature

  2. Solid Atoms vibrate in a nearly fixed position Gas Atoms apart, freely moving in the volume Microscopic Atoms • Atoms in matter are in constant motion. • Interaction of atoms determines the state of matter. • Liquid • Atoms close, but free to move around

  3. Macroscopic Properties • There are about 5 x 1024 atoms in a golf ball. • We track its motion as a whole, not as atoms. • Density and pressure apply to the whole object, not the atoms. • These are macroscopic properties. Microscopic properties: mass, position, velocity, energy Macroscopic properties: mass, position, velocity, energy and density, pressure, temperature

  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. Thermal Contact • Two cups of water are in contact. • Heat one cup • Compare macroscopic properties • If they are the same they are in thermal contact. • eg. metal cups • If different they are insulated. heater heater

  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. 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. C is in thermal equilibrium with B. Therefore, A is in thermal equilibrium with C. A B C

  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. Temperature requires a scale to compare different systems. The Kelvin (K) is the SI unit of temperature. Based on behavior of water Linear pressure scale Notdegrees Kelvin 10-4 K Superfluid liquid helium 4 K Helium boils 77 K Air boils 273 K Water melts 373 K Water boils 630 K Mercury boils 1000 K Copper melts 6000 K Surface of the sun 106 K Solar corona 108 K Hydrogen bomb Kelvin

  10. For everyday temperatures the Celsius scale (C) is used. Each C is the same magnitude as 1 K. The zero is different 0 C = 273.15 K Not quite T at P3 The English system uses the Fahrenheit scale (F). Ice point at 1 atm is 32. Boiling point at 1 atm is 212. Each F is 5/9 of a C. Temperature Scales

  11. Normal body temperature is 98.6 F. What is the equivalent in C and K? If your fever is 101.6 F, by how much has it risen in C and K? The general formula applies for a conversion between scales. TC = (5/9)(TF – 32) (5/9)(98.6 – 32.0) = 37.0 C T = TC + 273.15 = 310.2 K The difference use the fractional change. DTC = (5/9) DTF (5/9)(101.6 – 98.6) = 1.7 C DT = DTC= 1.7 K Body Temperature next

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