RP1 Specific Heat Capacity

Question 1

define the ‘specific heat capacity’ of a substance.

Answer 1

the amount of energy needed to raise the temperature of 1 kilogram of a substance by 1 degree celsuis.

Question 2

state the units for specific heat capacity

Answer 2

J°/C/kg
joules/degree celsius/kilogram

Question 2

how do you obtain the specific heat capacity for the metal you are measuring?

Answer 2

divide the inverse of the gradient by the mass of the metal block used.

Question 2

state the equation used to calculate the temperaute change when a substance is heated.

Answer 2

• ΔE = m c Δθ
• energy (J), mass (kg), specific heat capacity (J/kg/°C), temperature (°C)

Question 2

what safety precautions should be taken when carrying out this experiment?

Answer 2

• avoid touching the metal
• use a heatproof mat
• avoid spilling water near the power supply when adding drops to the thermometer hole

Question 3

how do you calculate the work done by the heater?

Answer 3

using the equation:
energy = power of heater x time
where energy is equivalent to the work done.

Question 3

if the power of the heater being used isn’t given, how can you calculate it?

Answer 3

by connecting it in parallel with a voltmeter, and in series with an ammeter, and then applying the equation:
P = I x V

Question 3

why do the metal blocks used in the experiment have two holes in them?

Answer 3

one for is for the heater and one is for the thermometer.

Question 3

what is the difference between heat capacity and specific heat capacity?

Answer 3

specific heat capacity is the heat capacity measured for a mass of 1 kg.

Question 3

what can be done to improve the reading given by the thermometer?

Answer 3

add a few drops of water in the hole with the thermometer to improve the thermal contact and ensure even heating.

Question 3

what graph do you plot with the data?

Answer 3

a graph of temerature against work done by the heater.

Question 3

what reading do you record during the experiement and how frequenctly?

Answer 3

you record the temperature value every 10 minutes from when the heater is inserted and switched on.

Question 4

once the block has initially warmed up, describe the graph of temperature against work done by the heater that should be obtained.

Answer 4

it should be a linear relationship and so should produce a straight line.

Question 4

what does the gradient of the graph represent?

Answer 4

the inverse of the heat capacity for the metal block.

Question 4

if you start timing from when you switch on the heater, why may the graph not initially be linear?

Answer 4

there will initially be some thermal inertia whilst the block and heater warm up.

Question 4

why should you wrap insulation around the outside of the metal block?

Answer 4

to reduce the heat loss to the environment and ensure the temperature reading is as accurate as possible.