Temperature, Heat, Thermal
Expansion, and Heat Transfer
PHYSICS I
Temperature
defn: what a
thermometer reads
• Average kinetic
energy reading of a
substance
• Fahrenheit,
Celcius, Kelvin
scales
•
Temperature Conversions
°F = (1.8 x °C) + 32
°C = (°F – 32) ÷ 32
K = °C + 273.15
Heat
 Defn: transfer of energy from one object to
another due to difference in temp.
 Coffee mug examples
 80°C coffee sitting on counter of kitchen
that is 26°C – what happens?
 What if cold (5°C) pop can sitting on the
counter of same kitchen?
Heat
 Internal Energy
A
substance contains internal energy…
NOT heat
 There is more internal energy in a bathtub
full of cold water than a red-hot pin (due to
the higher number of molecules; therefore,
bathtub has more kinetic energy)
 But! Heat flows from red-hot pin to tub
water
Measuring Heat
 Heat is a form energy (Joules)
 Calories:
calorie
Calorie
Heat required to raise 1g of
H2O by 1°C
Kilocalorie = heat required
to raise 1kg of H2O by 1°C
Unit of energy
Unit of energy
1 calorie = 4.184 joules
Used on food labels
Specific Heat
 Defn: quantity of heat required to change
temperature of a unit mass of substance by 1°
 Water (discussion – see map next slides)
Jet Stream?
Water – What do these graphs tell us?
Thermal Expansion
 As Temp. decreases => Substances contract (become
more dense)
 Except Water!



H2O MOST dense at 4°C
From 4°C to 0°C, water expands (becomes less dense)
Which is why ice floats
Conduction
 Heat transferred by successive collisions of atoms
 Good conductors of heat and electricity:
 Metals - #1 Ag, #2 Cu, #3 Al…
 Poor conductors:
 Wool, wood, styrofoam
 = insulators
 In February you drive by a house with snow on its
roof. Does the house have good insulation or poor?
Explain.
Convection
 Heat transferred
due to motion of
fluid
 Theory behind
plate tectonics
Global Wind Currents
At night or during day? Explain. What happens
during other half of earth rotation? Explain.
Radiant Energy
Radiant Energy in form of Electromagnetic waves