Temperature

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

Macroscopic Properties  There are about 5 x 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

Hot and Cold  Temperature is a macroscopic property of matter. Based on statisticsBased on statistics Doesn’t generally apply to single atomsDoesn’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 itemSingle atoms may have less energy in a hot item

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

Thermal Equilibrium  Two systems have the same temperature if they are in thermal equilibrium. Equilibrium between systemsEquilibrium between systems Measure of macroscopic propertiesMeasure of macroscopic properties  If two systems are not in thermodynamic equilibrium, they are not in thermal contact.

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

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.

Kelvin  Temperature requires a scale to compare different systems.  The Kelvin (K) is the SI unit of temperature. Based on behavior of waterBased on behavior of water Linear pressure scaleLinear pressure scale Not degrees KelvinNot degrees Kelvin KSuperfluid liquid helium 4 KHelium boils 77 KAir boils 273 KWater melts 373 KWater boils 630 KMercury boils 1000 KCopper melts 6000 KSurface of the sun 10 6 KSolar corona 10 8 KHydrogen bomb

Temperature Scales  For everyday temperatures the Celsius scale (  C) is used.  Each  C is the same magnitude as 1 K. The zero is differentThe zero is different 0  C = K0  C = K Not quite T at P 3Not quite T at P 3  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.

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