specific heat capacity

The amount of energy stored in or released from a system as its temperature changes can be calculated using the equation:

change in thermal energy = mass × speci f ic heat capacity × tem perature change

∆E = m c ∆θ

change in thermal energy, ∆E, in joules, J

mass, m, in kilograms, kg

specific heat capacity, c, in joules per kilogram per degree Celsius, J/kg °C

temperature change, ∆θ, in degrees Celsius, °C

what is specific heat capacity

The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.

The amount of energy stored in or released from a system as its temperature changes can be calculated using the equation:

change in thermal energy = mass × speci f ic heat capacity × tem perature change

∆E = m c ∆θ

change in thermal energy, ∆E, in joules, J

mass, m, in kilograms, kg

specific heat capacity, c, in joules per kilogram per degree Celsius, J/kg °C

temperature change, ∆θ, in degrees Celsius, °C

what is specific heat capacity

The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.

required practical 1: Investigating Specific Heat Capacity method

1. Start by assembling the apparatus, placing the heater into the top of the block

2. Measure the initial temperature of the aluminium block from the thermometer

3. Turn on the power supply and start the stopwatch

4. Whilst the power supply is on, the heater will heat up the block. Take several periodic measurements, eg. every 1 minute of the voltage and current from the voltmeter and ammeter respectively, calculating an average for each at the end of the experiment up to 10 minutes

5. Switch off the power supply, stop the stopwatch and leave the apparatus for about a minute. The temperature will still rise before it cools

6. Monitor the thermometer and record the final temperature reached for the block

the thermal energy supplied to block can be calculated using the equations:

E=QV and Q=It

where:

E=thermal energy, in joules (j)

• Q = Charge, in coulombs (C)

• I = current, in amperes (A)

• V = potential difference, in volts (V)

• t = time, in seconds (s)

  Combining the equations:

  • Rearrange to make Q the subject

    E=QV means that Q=E/V

  • Substitute into the Q = It equation

    Q=It

  • E/V=It

  • Rearrange to make E the subject

  • E=IVt

how do find change in energy

• To calculate ΔE:

∆E = IVθf - IVθi

• Where:

  • I = average current, in amperes (A)

  • V = average potential difference (V)

  • θ_f = final time, in seconds (s)

  • θ_i = initial time, in seconds (s)

how to avoid zero errors

-make sure voltmeter and ammeter initially set to zero

different types of random errors and how can be reduced

• Not all the energy transferred from the heater will be transferred to the block, some will be dissipated to the surroundings into the surroundings and some will be transferred to the thermometer (also part of the surroundings) 

  • This means the measured value of the specific heat capacity is likely to be higher than what it actually is

  • To reduce this effect, make sure the block is fully insulated

• A joulemeter could be used to calculate energy directly

  • This would eliminate errors from the voltmeter, ammeter and the stopwatch

• Make sure the temperature value is read at eye level from the thermometer, to avoid parallax error

• The experiment can also be repeated with a beaker of water of equal mass, the water should heat up slower than the aluminium block

safety considerations:

• Make sure never to touch the heater whilst it is on, otherwise, it could burn skin or set something on fire

  • Run any burns immediately under cold running water for at least 5 minutes

• Allow time for all the equipment, including the heater, wire and block to cool before packing away the equipment

• Keep water away from all electrical equipment

• Wear eye protection if using a beaker of hot water