IGCSE Chemistry 0620 Paper 63, May/June 2026

Name the item of apparatus labelled A in Figure 1.1.

State the general term used for the positive electrode, B, in Figure 1.1.

Give one observation, other than effervescence, during the electrolysis in Figure 1.1.

Suggest one change to the apparatus so the student can collect the gas made at electrode B in Figure 1.1.

Describe how the student can confirm that chlorine is made at electrode B in Figure 1.1.

Suggest one safety precaution the student must take when carrying out the experiment shown in Figure 1.1.

Use the information in the description of the experiments and the thermometer diagrams to complete Table 2.1. Calculate the temperature change using the equation shown. $$\text{temperature change}=\text{initial temperature}-\text{final temperature}$$ Table 2.1

On Figure 2.1, write a suitable scale on the y-axis and plot your results from Experiments 1 to 5. Draw a line of best fit.

On Figure 2.1, extrapolate your line of best fit to deduce the temperature change if $5.7\text{ g}$ of sodium thiosulfate powder is added to $20{\text{ cm}}^3$ of distilled water. Show clearly on Figure 2.1 how you worked out your answer. temperature change = .........................................°C

Suggest why sodium thiosulfate powder is used in the experiments rather than large lumps.

Explain why it would be an improvement to measure the volume of distilled water in a burette rather than a measuring cylinder.

State if the energy change when sodium thiosulfate powder is dissolved in distilled water is exothermic or endothermic. Use the results in Table 2.1 to explain your answer. energy change .......................................................................................................................... explanation ................................................................................................................................

Suggest why it is an improvement to use a lid on the polystyrene cup.

Suggest why the initial temperature of the distilled water does not need to be the same in each experiment.

The energy change in a reaction is calculated using the equation shown. $$\text{energy change}=\text{volume of water}\times 4.18\times \text{temperature change}$$ Calculate the energy change when sodium thiosulfate powder dissolves in Experiment 3. energy change = ....................................................... J

State what conclusion can be made about solution A from the observations in test 1.

State what conclusion can be made about solution A from the observations in test 2.

A flame test is used to confirm the identity of the cation in solution A. Describe how to carry out a flame test.

Suggest what the sodium carbonate reacts with in test 4 to produce carbon dioxide gas.

Tests on solid B Solid B is zinc sulfate. The student dissolves solid B in water to form solution B. The student divides solution B into three approximately equal portions into one boiling tube and two test-tubes. Complete the expected observations. To the first portion of solution B in the boiling tube, the student adds aqueous sodium hydroxide dropwise and then in excess. observations ..............................................................................................................................

To the second portion of solution B in a test-tube, the student adds $1{\text{ cm}}^3$ of dilute nitric acid followed by a few drops of aqueous barium nitrate. observations ........................................................................................................................

To the third portion of solution B in a test-tube, the student adds $1{\text{ cm}}^3$ of dilute nitric acid followed by a few drops of aqueous silver nitrate. observations ........................................................................................................................