Specification Point 3.3:
Calculate the heat energy change from a measured temperature change using the expression q = mc△t
Heat Energy Change
Heat energy change:
Data from a calorimetry experiment can be used to calculate the heat energy change of a reaction.
Q – energy transferred to water
m – mass of water heated *if water is not used, this is replaced by the mass or volume of other solutions
c – the specific heat capacity – is the amount of heat needed to raise the temperature of 1 gram of a substance by 1 oC. For water, the value is 4.18 J g-1C-1 (joules per gram per degree Celsius).
∆T – change in temperature of water
The energy from burning 0.5 g of propane was transferred to 100 cm3 of water to raise its temperature by 20°C. Calculate the heat energy change (in kJ)
Mass of Water = 100 cm3
Heat capacity of Water = 4.2 j / g / C
Temperature rise = 20°C
Energy transferred = 100 x 4.2 x 20 = 8400 J
*1000 J = 1 kJ
So 8400 J = 8.4 kJ
Energy transferred = 8.4 kJ
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Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.
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