Practical: Investigating Temperature Changes (Edexcel IGCSE Science (Double Award): Chemistry): Revision Note

Practical: Investigating Temperature Changes

Simple calorimeter 

A lid is required to prevent heat loss

• The same simple calorimeter can be used to investigate temperature changes in different processes

• Use an insulated container with a lid to reduce heat transfer to the surroundings.

• Measure the initial temperature before the substances are mixed.

• Measure the highest or lowest temperature reached after mixing.

  • A temperature increase indicates an exothermic process.

  • A temperature decrease indicates an endothermic process.

Example 1: Neutralisation reactions - Hydrochloric Acid and Sodium Hydroxide

Aim:

• To perform a calorimetry study of the neutralisation reaction between HCl and NaOH

Apparatus:

• Dilute hydrochloric acid

• Dilute sodium hydroxide solution

• Simple calorimeter shown above

• 25 cm³ measuring cylinder

• Thermometer & stirrer

Method:

1. Using a measuring cylinder, place 25 cm³ of the NaOH solution into the calorimeter

2. Measure and record the temperature of the solution

3. Add 5 cm³ of the dilute HCl and stir

4. Measure and record the highest temperature reached by the mixture

5. Repeat steps 1 – 4 increasing the amount of acid added by 5 cm³ each time

Results:

• Record your results in a suitable table

• Plot a graph of the results

• Draw a line of best fit

• Use the graph to determine which volume of acid produces the greatest temperature change

Conclusion:

• Compare the initial temperature with the highest temperature reached

• A temperature increase shows that energy has been transferred to the surroundings

• The neutralisation reaction is therefore exothermic

Example 2: Displacement reactions - Iron and Copper(II) Sulfate

• The same simple calorimeter setup can also be used to investigate the temperature change during a displacement reaction

• Only the chemicals being investigated are changed

Aim:

• To investigate the temperature change when iron reacts with copper(II) sulfate solution

Apparatus:

• Copper(II) sulfate solution

• Iron powder or iron filings

• Simple calorimeter shown above

• 25 cm³ measuring cylinder

• Balance

• Thermometer & stirrer

Method:

1. Place 25 cm³ of copper(II) sulfate solution into the insulated container

2. Measure and record the initial temperature of the solution

3. Add a measured mass of iron and stir

4. Measure and record the highest temperature reached

5. Repeat the experiment using different measured masses of iron

Results:

• Record your results in a suitable table

• Compare the temperature changes obtained

• Identify which quantity of iron produces the greatest temperature change

Conclusion:

• A rise in temperature shows that energy has been transferred to the surroundings

• The displacement reaction between iron and copper(II) sulfate is therefore exothermic

Example 3: Salts dissolving in water — Ammonium Nitrate in Water

• The same simple calorimeter setup can also be used to investigate the temperature change when a substance dissolves

Aim:

• To investigate the temperature change when ammonium nitrate dissolves in water

Apparatus:

• Water

• Ammonium nitrate

• Simple calorimeter shown above

• 25 cm³ measuring cylinder

• Balance

• Thermometer & stirrer

Method:

1. Place 25 cm³ of water into the insulated container

2. Measure and record the initial temperature of the water

3. Add a measured mass of ammonium nitrate

4. Stir until the ammonium nitrate has dissolved

5. Measure and record the lowest temperature reached

6. Repeat the experiment using different measured masses of ammonium nitrate

Results:

• Record your results in a suitable table

• Identify which mass of ammonium nitrate produces the greatest temperature change

Conclusion:

• A fall in temperature shows that energy has been absorbed from the surroundings

• Dissolving ammonium nitrate in water is therefore endothermic