Required practical 1 - Specific heat capacity Flashcards
Define the ‘specific heat capacity’ of a substance
The amount of energy needed to raise the temperature of 1kg of a substance by 1°C.
State the units for specific heat capacity
J/kg°C
State the equation for specific heat capacity
ΔE = m c Δθ
Energy (J), mass (kg), specific heat capacity (J/kg°C)
If the power of the heater being used isn’t given, how can you calculate it?
By connecting it in parallel with a voltmeter, and in series with an ammeter and then applying the equation:
P x I V
Why do the metal blocks used in the experiment have 2 holes in them?
One is for the heater and one is for the thermometer.
What can be done to improve the reading given by the thermometer?
Add a few drops of water or oil in the hole with the thermometer to improve thermal contact and ensure heating.
What reading do you record during the experiment and how frequently?
You record the temperature value every 10 minutes from when the heater is inserted and switched on.
Record initial temperature and final temperature for specific heat capacity.
What graph do you plot with the data?
A graph of temperature against work done by the heater.
How do calculate the work done by the heater?
Energy = power of heater x time
Where energy is equivalent to the work done.
Once the block has initially warmed up, describe the graph of temperature against work done by the heater that should be obtained.
It should be a linear relationship and should produce a straight line.
If you start timing from when you switch on the heater, why may the graph not initially be linear?
There will be some thermal inertia whilst the block and heater warm up.
What does the gradient of the graph represent?
The inverse of the heat capacity of the block.
How do you obtain the specific heat capacity for the metal you are measuring?
Divide the inverse of the gradient by the mass of metal block used.
or
Find mass of material and multiply by change in temperature.
Divide the work done/energy by mass x change of temperature.
Use equation c = ΔE / m Δθ
What is the difference between heat capacity and specific heat capacity?
Specific heat capacity is the heat capacity measured for a mass of 1kg.
Why should you wrap insulation around the outside of the metal block?
To reduce the heat loss to the environment and ensure the temperature reading is as accurate as possible.
