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Specific Heat Capacity

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Specific Heat Capacity Or the amount of energy needed to heat substances up Specific Heat Capacity can be thought of as a measure of how much heat energy is needed to ... – PowerPoint PPT presentation

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Title: Specific Heat Capacity


1
Specific Heat Capacity
  • Or the amount of energy needed to heat substances
    up

2
  • Specific Heat Capacity can be thought of as a
    measure of how much heat energy is needed to warm
    the substance up.
  • You will possibly have noticed that it is easier
    to warm up a saucepan full of oil than it is to
    warm up one full of water.

3
  • Specific Heat Capacity (C) of a substance is the
    amount of heat required to raise the temperature
    of 1g of the substance by 1oC (or by 1 K).
  • The units of specific heat capacity are J oC-1
    g-1 or J K-1 g-1. Sometimes the mass is expressed
    in kg so the units could also be J oC-1 g-1 or
  • J K-1 kg-1

4
  • The next table shows how much energy it takes to
    heat up some different substances.
  • The small values show that not a lot of energy is
    needed to produce a temperature change, whereas
    the large values indicate a lot more energy is
    needed.

5
  • Approximate values in J / kg K of the Specific
    Heat Capacities of some substances are
  • Air 1000 Lead 125
  • Aluminium 900 Mercury 14
  • Asbestos 840 Nylon 1700
  • Brass 400 Paraffin 2100
  • Brick 750 Platinum 135
  • Concrete 3300 Polythene 2200
  • Cork 2000 Polystyrene 1300
  • Glass 600 Rubber 1600
  • Gold 130 Silver 235
  • Ice 2100 Steel 450
  • Iron 500 Water 4200

6
The equation
  • The amount of heat energy (q) gained or lost by a
    substance mass of substance (m) X specific heat
    capacity (C) X change in temperature (?T)
  • q m x C x ?T

7
An example of a calculation using the specific
heat capacity equation
  • How much energy would be needed to heat 450
    grams of copper metal from a temperature of
    25.0C to a temperature of 75.0C?
  • (The specific heat of copper at 25.0C is 0.385
    J/g C.)

8
  • Explanation
  • The change in temperature (?T) is
  • 75C - 25C 50C
  • Given mass, two temperatures, and a specific heat
    capacity, you have enough values to plug into the
    specific heat equation
  • q m x C x ?T .
  • and plugging in your values you get
  • q (450 g) x (0.385 J/g C) x (50.0C)
  • 8700 J

9
Some good websites
  • http//www.s-cool.co.uk/gcse/physics/energy-transf
    ers/types-of-energy-transfers.htmltypes-of-energy
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