Specific Heat Capacity
What’s a property?
• It’s a characteristic of a given substance
• All substances of the same type will share
these characteristics.
• They are often very useful if you need to
identify an unknown substance
• Examples?
One essential property of all
substances is called
What is it?
• It’s the amount of energy that’s required
to raise the temperature of one gram of
a substance by 1°Celsius
• Every substance has it’s own specific
heat capacity. For example...
Substance
Air
Aluminium
Copper
Gold
Iron
Mercury
NaCl
Ice
Water
J/g °C
1.01
0.9
0.38
0.13
0.45
0.14
0.86
2.03
4.18
What does this mean?
• You need 4 joules of energy to raise the
temperature of a gram of water (about a mL)
by one degree.
• BUT you only need 1 joule to raise the
temperature of a gram of air by the same
amount.
• This explains why air heats up and cools
down so much faster than water.
Calculating specific heat
capacity
Q = Energy in joules
c = specific heat capacity
m=Mass
∆t = the temperature change
OR Tfinal - Tinitial
Further reading: p. 427-431
Assignment:
Using the information in your texts, invent
3 specific heat problems for each of
types 1, 2 and 3
1. Don’t know Q
• You leave a glass containing 500g of water outside on a sunny
day. When the water came out of the fridge it had a temperature
of 5°C. After an hour, it’s temperature has risen to 20°C. You
know from science class that the specific heat of water is
4.18J/g°C. How much energy was added to the water?
2. Don’t know m
• You are working with a piece of iron in the lab, but
the scale is broken so you can’t find the mass. You
have been heating the metal. You know that you
have added 2000J of energy and the temperature of
the iron has increased by 100°C. If the specific heat
is 0.45J/g°C, find the mass
3- Don’t know c
• You have 100g of an unknown substance. You have
added 2030J of energy to the sample and the
temperature has risen 10°C. What is the specific
heat of the sample?
4- Don’t know ∆t
• You apply 3000J of energy to a sample of aluminum
which has a mass of 50g. How much will the
temperature increase if the specific heat capacity of
aluminum is 0.9J/g °C