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
There are about 5 x 1024
atoms in a golf ball.
We track its motion as a mass, position, velocity, energy
whole, not as atoms.
Density and pressure apply
to the whole object, not the
atoms. mass, position, velocity, energy
These are macroscopic and
density, pressure, temperature
Hot and Cold
Temperature is a
macroscopic property of
• Based on statistics
• Doesn’t generally apply to
Hot matter has more energy
per atom on average than
• Single atoms may have less
energy in a hot item
heater Two cups of water are in
• Heat one cup
• Compare macroscopic
If they are the same they are
heater in thermal contact.
• eg. metal cups
If different they are insulated.
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.
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.
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.
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
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
For everyday temperatures The English system uses the
the Celsius scale (C) is Fahrenheit scale (F).
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
TF TC 32
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
The difference use the
• DTC = (5/9) DTF
• (5/9)(101.6 – 98.6) = 1.7 C
• DT = DTC = 1.7 K