1. 5.4.3 Calorimeters
How they work
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2. Heat of Combustion
Heat produced when 1 mole of a substance is completely burned in excess oxygen
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3. Calorimeter measures heat produced when substances burn
Heat produced is calculated using the formula
H = mc 
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4. H = heat [produced or change] c = specific heat capacity
H = mc
H = heat [produced or change]
c = specific heat capacity
m = mass in kg
 = temperature change
Assume all the heat from the reaction goes into the calorimeter
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5. Sometimes m and c are combined to give the Heat Capacity of the apparatus
In this case one only has to multiply the temperature change by the heat capacity to calculate the heat produced.
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6. Simple calorimeter Thermometer Draught shield Calorimeter with water
Small container of fuel
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7. Inaccurate because
Much heat escaped [convection in air / radiation from can / evaporation of water]
Draught shield makes it much more accurate
We did not account for heat capacity of tripod or clamp etc. in our calculations
Combustion was incomplete [carbon (soot) on base of calorimeter]
Slow gave time for heat to escape
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8. Suitable Reactions
Three things must apply if a reaction is to be suitable for study in a calorimeter
It must be rapid
It must go to completion
Must have no side reactions
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9. Bomb Calorimeter To get accurate results we use a Bomb Calorimeter
Oxygen pumped in under pressure to ensure rapid and complete combustion
Often so rapid that it exploded
Hence the name “ bomb calorimeter”
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10. SCC Science Dept

11. Bomb Calorimeter is accurate because the reaction is fast complete
there are no side reactions
and no heat loss
even the amount of heat to start burning can be worked out exactly and removed.
Used to measure calorific value of food
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12. Define Heat of combustion [4] Define Heat of formation [4]
Define Heat of reaction [4]
Give 3 characteristics of exothermic reaction [3]
Opposite of exothermic and example [2]
Three characteristics a reaction needs to be suitable for use in bomb calorimeter [3]
What is heat capacity? [2]
What is the formula to calculate heat produced? [3]
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13. What is heat capacity? [1] mc H = [1] mc
Define Heat of combustion [4] heat change /one mole / burned completely / in excess oxygen
Define Heat of formation [4] heat change / when 1 mole formed / from its elements / in standard states
Define Heat of reaction [4] heat change / number of moles / in balanced equation / react compleatly
Give three characteristics of exothermic reaction [3] gives out heat / feels hot / delta H is -ve
Opposite of exothermic and example [3] endothermic / sherbet or ammonium chloride / dissolving in water
Three characteristics a reaction needs to be suitable for use in bomb calorimeter [3] fast / complete / no side reactions
What is heat capacity? [1] mc
H = [1] mc
SCC Science Dept