TEMPERATURE AND HEAT
TEMPERATURE
Temperature is the intensity or degree of heat generally
measured by an instrument called a thermometer.
Heat flows spontaneously from an object at a higher
temperature to an object at a lower temperature.
THERMOMETRY
Temperature measures the average kinetic energy of the particles in a
substance.
At the same temperature the average kinetic energy of the particles in a
substance is the same.
Kinetic Energy = ½ mv2
Lighter molecules move faster
Heavier molecules move slower
An increase in temperature causes molecules to move faster.
An decrease in temperature causes molecules to move slower.
FIXED POINTS ON A THERMOMETER
Freezing point of water: temperature at which water changes from a
liquid to a solid. (ice-water equilibrium) at 1 atmosphere of pressure
(standard pressure)
Boiling point of water: temperature at which water changes to a gas.
(steam-water equilibrium) at 1 atmosphere of pressure.
The space between these reference points is divided evenly into
degrees.
Absolute zero: temperature at which all molecular motion ceases.
Theoretically the lowest possible temperature.
THREE TEMPERATURE SCALES
Celsius /Fahrenheit Conversions
1000C=1800F
0C=
0F=
5/9(F-32)
9/5C + 32
Celsius/Kelvin Concersions
1000C=100K
0C=K-273
K=0C+ 273
(table T)
PRACTICE TIME
Try These
Answers:
1. 59 0 F = ? 0C
1.
2.
60 0C= ? 0F
2. 140
3.
10 0 C = ? K
3. 283
4.
-23 0 C = ? K
4. 250
5.
300 K= ? 0 C
5. 27
15
HEAT
Heat is measured quantitatively by the change in temperature it can
produce in a given mass of water.
Non-SI unit for heat is the calorie.
Calorie is defined as the amount of heat needed to raise the temperature of
1.0 gram of water by 1.0 degree Celsius,
1 kcal =1000 calories (food calorie)
SI unit for heat is the joule.
1 calorie = 4.18 joules
 Calorimeter is used to determine the quantity of heat given off or absorbed
in a chemical reaction.
SPECIFIC HEAT
Specific heat of a substance is the number of calories/joules required to raise
the temperature of one gram of a substance by one degree Celsius.
Specific heat of water is 1.0 calorie/gram 0C = 4.18 Joules/gram
0
C (table B)
Specific heat of aluminum is .214 calories/gram 0 C = .895 Joules/gram 0 C
Heat gained or lost by a substance=
(mass of substance)(specific heat for substance)(change in temperature)
Table T
HEAT EQUATION: Q= M C ▲T
 Try
this: How many calories are released when 50.0 grams
of water are cooled from 75.0 to 35.0 degrees Celcius?
Solution:
Q= m c ▲T
Q= (50.0 grams) (4.18 Joules/gram 0 C)(40.0 0 C)
Q= 8360 Joules