P1 Specific Heat Capacity (page 169) Flashcards
What is meant by ‘Specific Heat Capacity’?
its just a sciencey way of saying how hard it is to heat somehing up….
Do different materials have different specific heat capacities?
Yes
Why is more energy needed to be transferred to the thermal energy stores of some materials, give an example.
to increase their temperature .
E.g. You need 4200 J to warm 1kg of water by 1°C.
Materials that need to gain lots of energy in their thermal energy stores to warm up also transfer loads of energy when they what?
when they cool down again.
They can ‘store’ lot a of energy
What is ‘Specific Heat Capacity’?
it is the amount of energy needed to raise the temperature of 1kg of a substance by 1°C.
What is the equation that links energy transferred to ‘specific heat capacity’?
Look at diagram on page 169
(triangle) E = mc(triangle)(zero with line)
How do you investigate a solid material (e.g. copper)? (this is a pracical)
What is the fist stage of the practical?
1) you will need a block of the material with two holes in it (for the heater and thermometer to go into, see diagram 2 on page 169)
2) Measure the mass of the block, then wrap it in an insulating layer (eg. a thick layer of newspaper) to reduce the energy transferred from the block to the surroundings). Insert the thermometer
and the heater as shown on page 169 diagram 2.
3) Measure the initial temperature of the block and set the potential difference, V, of the power supply to be 10 V. Turn on the power supply and start a stop watch.
4) When you turn on the power, the current in the circuit (i.e. the moving charges) does work on the heater, transferring energy electrically from the power supply to the heater’s thermal energy store. This energy is then transferred to the material’s thermal energy store by heating, causing the material’s temperature to increase.
5) As the block heats up, take readings of the temperature and current, I, every minute for 10 minutes. You should find that the current through the circuit doesn’t change as the block heats up.
6) When you’ve collected enough readings (10 should do it), turn off the power supply. Using your measurement of the current, and the potential difference of the power supply, you can calculate he power supplied to the heater, using P = VI (see page 188). You can use this to calculate how much energy E, has been transferred to the heater at the time of each temperature reading using the formula E = Pt, where t is the time in seconds since the experiement.
After the practical investigation of the specific heat capacities, how can you record your research?
if you assume all the enrgy supplied to the heater has been transferred to the block, you can plot a graph of energy transferred to the thermal energy store of the block against temperature. It should look like diagram 3 on page 169.
(you may or may not get the curved bit at the beginning).
Find the gradient of the straight part of the graph, from using the equation symbols on point 8 on page 169).
You can repeat this experiment with different materials to see how their specific heat capacities compare.
How can you investigate the specifit heat capacity of liquids?
You just place the heater and thermometer in an insulated beaker filled with a known mass of the liquid.
Find the final temperature of 5kg of water, at an initial temperature of 5°C, after 50 kj
J of energy has been transferred to it. The specific heat capacity of water is 4200 J/kg°C (3 marks)
see detailed answer on page 256. (p.169)
