Practical
Evaluating the method
1.11
This experiment is used to find the specific heat capacity of brass by assuming that all the thermal energy transferred from the hot water increases the temperature of the lump of brass. We are equating the decrease in thermal energy store of the water to the increase in thermal energy store of the brass. If this assumption is not true, the method will not be valid. 5
The lump of brass has to be moved from one beaker to the other. Consider how this step in the method could affect the accuracy of the results.
KEY INFORMATION
6
The energy transferred from the water to the brass will cause the lump of brass in the second beaker to get hotter. Why will the energy transferred to the lump of brass not be stored there permanently?
7
What are the implications of your answers to questions 5 and 6 for the way the experiment is carried out?
When thinking about this experiment, remember that energy tends to move from hotter areas to cooler ones.
8
Why is it important that the lump of brass is covered in water in the second beaker?
Using the data to calculate a value for SHC We find the specific heat capacity of brass by calculating the energy transferred into the water when its temperature increases and equating that to energy transferred out of the brass when its temperature decreases. Decrease in energy stored by brass = increase in energy stored by water mwater × cwater × temperature increasewater = m brass × c brass × temperature decrease brass The final temperature of the water and brass is the same (they reach thermal equilibrium). As long as we know the values of the mass of water, mass of brass, specific heat capacity of water and initial temperatures of the water and brass, we can find the unknown value for the specific heat capacity of brass. 9
There is 250 g of water (cwater = 4200 J/kg ° C) in the second beaker and its temperature rises from 17 ° C to 26 ° C. Determine how much energy has been transferred into it.
10 How much energy can we assume has been transferred out of
the brass when it is put into the second beaker? 11 If the brass had been in boiling water, by how much would its
temperature have decreased? 12 The lump of brass has a mass of 150 g. Calculate the specific heat
capacity of brass. 13 Explain why is this method likely to give a lower value for the
specific heat capacity than its true value.
Google search: ‘specific heat capacity by method of mixtures’
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8/11/16 7:33 AM