Specific Heat

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Chapter 3

• Specific Heat
• Part 1 and Part 2

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Specific Heat

• Different substances require different amounts of
  heat to change their temperature.
• In general the specific heat of a substance
  indicates how hard something is to heat up or
  cool down.
• Scientifically speaking the specific heat is the
  amount of heat required to change the temperature
  of 1 gram of a substance by 1ºC.

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• Which substance is the easiest to heat up or cool
  down?

4
?

• Which substance is the easiest to heat up or cool
  down?

5

• Which substance is the hardest to heat up or cool
  down?

6
?

• Which substance is the hardest to heat up or cool
  down?

7
?

• Which substance is the hardest to heat up or cool
  down?
• How might we observe the high specific heat of
  water?

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Cannonball Champion
9
?

• Scientific interpretation of the specific heat of
  water.

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The specific heat of water

• The specific heat of water is 4.184 J/gºC.
• To simplify our discussion we will round this to
  4 J/gºC.

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The specific heat of water

• If we have one gram of water at 25ºC and we add
  4J of energy to it what will the temperature be?
• Answer 26ºC

12
The specific heat of water

• If we have two grams of water at 30ºC and we
  remove 16J of energy from it what will the
  temperature be?
• Answer 28ºC

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The specific heat of water

• The high specific heat of water has many
  implications to our everyday lives.

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Importance of Waters High Specific Heat

• Maintenance of Body Temperature

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Importance of Waters High Specific Heat

• Heat Storage on a Larger Scale.

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Importance of Waters High Specific Heat

• Temperature fluctuations that permit life.

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Heat and Temperature Video (Physics
Demonstrations 16)
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How Much Heat?

• I want to heat some water.
• What do I need to know in order to determine the
  amount of heat required?
• Mass of water.
• Temperature Change
• Specific Heat of Water

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H m ?T Cp Heat (mass) x (change in
temperature) x (specific heat)
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Kilojoules

• kilo (k) 1000
• kJ 1000 J
• 4.08 kJ 4080 J

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• How much heat is necessary to heat 258g of water
  from 25.0ºC to 100.0ºC?
• (258g)(75.0ºC)(4.184J/gºC) 80,960.4J 81,000J
• 81.0 kJ

22

• How much heat must be removed to cool 1058g of
  copper from 325.0ºC to 18.0ºC?
• (1058g)(307.0ºC)(0.385J/gºC) 125,050J
  125,000J
• 125 kJ

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How much water do I have?
52.8 ml 52.8 cm3 or 52.8 g
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• The mass of an unknown metal is 14.9 g. It is
  heated to 100.0?C and dropped into 75.0 mL of
  water at 20.0?C. The final temperature of the
  system is 28.5?C. What is the specific heat of
  the metal?

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• The mass of unknown metal is 17.19 g. It is
  heated to 100.00?C and dropped into 25.00 mL of
  water at 24.50?C. The final temperature of the
  system is 30.05?C. What is the specific heat of
  the metal?

Heat gained by the water Heat lost by the
metal m ?T Cp m ?T Cp (25.00g)(5.55C)(4.184
J/g ?C) (17.19g)(69.95C)(x)
Cp 0.483 J/g C
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Homework

• Worksheet Chapter 3 3