Required Practical: Investigating Temperature Changes (OCR GCSE Chemistry A, Combined (Gateway Science Suite)): Revision Notes

This experiment aims to investigate how changing the concentration of an acid affects the temperature change during a reaction. By using an insulated cup, the experiment measures the temperature changes as reactants are mixed, providing insights into the energy changes that occur.

Method:

1. Prepare the Hydrochloric Acid:

• Measure 25 cm³ of hydrochloric acid.
• Heat the acid to 25°C.

2. Set Up the Reaction:

• Pour the heated hydrochloric acid into a polystyrene cup. The insulation provided by the cup helps minimise heat loss to the surroundings, ensuring a more accurate measurement of temperature change.
• Add 1 g of powdered magnesium to the cup.

3. Monitor the Temperature:

• Place a lid over the cup, ensuring that a thermometer is inserted through the lid so that its bulb is fully immersed in the reaction mixture.
• Place the cup inside a beaker filled with cotton wool to further insulate the reaction mixture.
• Measure and record the temperature every 30 seconds for 5 minutes. Record the highest temperature reached during the reaction.

4. Repeat the Experiment:

• Repeat steps 1 to 5, each time increasing the concentration of the hydrochloric acid by 0.2 g/dm³.
• Start with a concentration of 0.2 g/dm³ and increase it up to 1.0 g/dm³.

5. Analyse the Results:

• Compare how the temperature change varies with different concentrations of hydrochloric acid.
• Determine the relationship between the concentration of the acid and the energy change of the reaction.