# Temperature Temperature Microscopic Atoms  Atoms in matter are in

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```					Temperature
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
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
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
Thermal Contact
heater               Two cups of water are in
contact.
• Heat one cup
• Compare macroscopic
properties

   If they are the same they are
heater                in thermal contact.
• eg. metal cups

   If different they are insulated.
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.
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.
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          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
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
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.
• DTC = (5/9) DTF
• (5/9)(101.6 – 98.6) = 1.7 C
• DT = DTC = 1.7 K

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