Specific Heat Capacity (SQA National 5 Physics): Exam Questions

A set of hair straighteners contain a pair of titanium plates that are heated.

One of the titanium plates has a mass of 1.90 × 10⁻² kg.

The titanium plate is at an initial temperature of 25 °C. The hair straighteners are switched on and the titanium plate reaches a temperature of 235 °C.

The titanium plate has a specific heat capacity of 532 J kg⁻¹ °C⁻¹.

(i) Calculate the minimum energy required to raise the temperature of the titanium plate from 25 °C to 235 °C.

[3]

(ii) Explain why the energy supplied to the titanium plate is greater than the heat energy gained by the plate.

[1]

The titanium plates are now replaced with ceramic plates.

Suggest two reasons why the time taken to heat the ceramic plates from 25 °C to 235 °C is different to the time taken to heat the titanium plates from 25 °C to 235 °C.

An electric iron operates at 230 V a.c.

The power rating of the iron is 1750 W.

When the iron is switched on, it takes 72.0 s for the soleplate to reach the correct temperature.

During this time, 126 000 J of energy is transferred to the soleplate.

(i) The soleplate is made from aluminium.

The mass of the soleplate is 0.650 kg.

The initial temperature of the soleplate is 22 °C.

Determine the maximum temperature reached by the soleplate.

[4]

(ii) Explain why the maximum temperature reached by the soleplate will be less than that calculated in (b) (i).

[1]

The hot water dispenser heats 0·250 kg of water for each cup.

(i) Calculate the minimum energy required to heat 0·250 kg of water from an initial temperature of 20·0 °C to its boiling point.

[3]

(ii) As the water is dispensed into the cup, steam is released.

Determine the maximum mass of steam that can be produced while the water for one cup is being heated.

[4]

(iii) Explain why, in practice, the mass of steam produced is less than calculated in (ii).

[1]

A student carries out an experiment to determine the specific heat capacity of copper.

The setup used by the student is shown.

The student heats the copper block for 5 minutes.

The temperature of the block increases by 14 °C.

The value of the specific heat capacity of copper determined by the student using this method is found to be inaccurate.

Which of the following changes would improve the accuracy of this experiment?

Bottles used for feeding babies require sterilising before use.

For one design of bottle, a microwave oven is used to heat water in the bottle. This produces steam, which sterilises the bottle.

To sterilise the bottle, 0.020 kg of water is placed in the base of the bottle, before being heated in the microwave oven.

The initial temperature of the water is 6.3 °C.

(i) Calculate the energy required to heat the water to its boiling point.

[3]

(ii) Determine the minimum energy required to produce 0.014 kg of steam from 0.020 kg of water at an initial temperature of 6.3 °C.

[1]

A student carries out an experiment, using the apparatus shown, to determine a value for the specific heat capacity of water.

The student switches on the power supply and the immersion heater heats the water.

The joulemeter measures the energy supplied to the immersion heater.

The student records the following measurements.

energy supplied to immersion heater = 21 600 J

mass of water = 0·50 kg

initial temperature of the water = 16 °C

final temperature of the water = 24 °C

reading on voltmeter = 12 V

reading on ammeter = 4∙0 A

(i) Determine the value of the specific heat capacity of water obtained from these measurements.

[3]

(ii) Explain why the value determined from the experiment is different from the value quoted in the data sheet.

[1]