Practical questions

You will complete 12 required Specified Practical Activities if you are studying GCSE Chemistry, and 27 if you are studying GCSE Combined Science (nine of these are in Chemistry). These help you develop some key practical techniques in Chemistry.

You could be asked questions about the apparatus, methods, safety precautions, results, analysis and evaluation of these experiments.

There is one Specified Practical Activity in the 'Energy changes in chemistry' section:

  • determination of the amount of energy released by a fuel

Questions courtesy of Eduqas.

Sample question 1 - Foundation

Question

Olwen wants to answer the scientific question below:

When magnesium is added to dilute hydrochloric acid, how does acid concentration affect temperature change?

Tick one box in each row of table 1 to identify the different types of variable in the investigation. [3 marks]

Variable✔ if this is the independent variable ✔ if this is the dependent variable✔ if this is a control variable
Acid concentration
Volume of acid
Temperature change
Mass of magnesium
Variable✔ if this is the independent variable ✔ if this is the dependent variable✔ if this is a control variable
Acid concentration
Volume of acid
Temperature change
Mass of magnesium

Sample question 2 - Foundation

Question

Different lengths of magnesium ribbon were put into separate beakers each containing 25 cm3 dilute hydrochloric acid and the temperature measured.

The initial temperature of the acid in each beaker was 16°C.

The results are shown in the table below. Two temperatures are missing.

Length of magnesium ribbon2 cm4 cm6 cm8 cm10 cm12 cm
Final temperature20°C23°C28°C33°C35°C______°C
Initial temperature16°C16°C16°C16°C16°C16°C
Temperature rise4°C7°C12°C17°C19°C______°C

Complete the table by using the thermometer reading shown below.

Thermometer reading with 12 cm of magnesium

[2 marks]

  • final temperature 42°C [1]
  • temperature rise 26°C [1]

Sample question 3 - Higher

Question

An investigation was carried out to find out which alcohol gives out the most energy when burned.

A beaker containing 100 g of water was heated using an alcohol in a spirit burner.

Heating alcohol with a spirit burner

In each case sufficient alcohol was burned to increase the temperature of 100 g of water by 40°C. Each alcohol was tested three times and the mean mass required was calculated.

The results for butanol are shown in the table below.

AlcoholTotal mass before (g)Total mass after (g)Mass of alcohol required (g)Mean mass of alcohol required (g)Energy released (kJ/g)
butanol177.05175.591.46 0.98
175.26174.201.06
174.94174.030.90

a) The energy in joules (J) released by 1.0 g of an alcohol can be calculated using the formula:

energy released = \frac{\textup{mass~of~water} \times 4.2 \times \textup{temperature~change}}{\textup{mean~mass~of~alcohol~required}}

Use this formula to calculate the energy released in kJ/g when 0.98 g of butanol is burned. Give your answer to three significant figures. [2 marks]

b) One of the mass values for butanol was not used in calculating the mean mass required.

Identify this value and suggest one experimental error that would explain why this result was recorded. [2 marks]

a) 17143 J [1]

17.1 kJ/g [1] - must be given to 3 significant figures

b) First reading / 1.46 [1]

Heat loss here was greater than for other measurements, eg bigger gap between flame and beaker/more than 100 g of water measured into beaker [1]

Sample question 4 - Higher

Question

An investigation was carried out to find out which alcohol gives out the most energy when burned. The diagram below shows the apparatus used.

Heating alcohol with a spirit burner

Describe and explain two improvements that could be made to the method to obtain experimental values closer to the theoretical values of energy released. [4 marks]

The following is a list of valid points that could be included in your answer. Any two pairs below, with a mark for improvement and a mark for explanation in each case, are valid answers.

  • Improvement: Enclose apparatus/reduce drafts
  • Explanation: Less heat lost between flame and beaker
  • Improvement: Copper can instead of glass beaker/better conductor
  • Explanation: More heat transferred to water
  • Improvement: Improve insulation/lag beaker/lid on beaker
  • Explanation: Less heat lost after transfer to water

[4]