Starter quiz
- What is an exothermic reaction?
- A reaction that absorbs energy from the surroundings
- A reaction that neither releases nor absorbs energy
- A reaction that releases energy to the surroundings ✓
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- What is an endothermic reaction?
- A reaction that absorbs energy from the surroundings ✓
- A reaction that neither releases nor absorbs energy
- A reaction that releases energy to the surroundings
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- What is the pH range of acidic solutions?
- 0 to 14
- 0 to 6 ✓
- 7 to 14
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- What is the pH range of alkaline solutions?
- 0 to 6
- 7 to 14
- 8 to 14 ✓
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- What does a pH indicator do?
- Changes colour to show if a solution is acidic or alkaline ✓
- Measures the temperature of a solution
- Reacts with acids and bases to produce gas
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- What is a neutralisation reaction?
- A reaction between a base and a metal
- A reaction between an acid and an alkali to form water and a salt ✓
- A reaction between two acids
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Exit quiz
- In the neutralisation practical, why is it important to measure the initial temperature of the hydrochloric acid?
- To check the purity of the acid
- To determine the temperature change during the reaction ✓
- To ensure the acid is at room temperature
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- What is the primary reason for the temperature increase during a neutralisation reaction?
- Energy is absorbed as bonds break in the acid and alkali
- Energy is released as gas forms
- Energy is released as heat when bonds form between water molecules ✓
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- What is the dependent variable in the neutralisation experiment?
- The amount of salt formed
- The temperature change of the reaction mixture ✓
- The volume of hydrochloric acid used
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- Why is it important to use a polystyrene cup when conducting the neutralisation experiment?
- Polystyrene changes colour to indicate the completion of the reaction
- Polystyrene is an insulator that minimises heat loss to the surroundings ✓
- Polystyrene reacts with the acid to produce more accurate results
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- How can you experimentally determine whether a neutralisation reaction is exothermic or endothermic?
- Measure the pH change before and after the reaction
- Measure the temperature change of the reaction mixture before and after ✓
- Observe the colour change of the indicator
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- If 25 cm³ of hydrochloric acid reacts with 25 cm³ of sodium hydroxide, what will be the final pH of the solution?
- Approximately 1, indicating a highly acidic solution
- Approximately 14, indicating a highly alkaline solution
- Approximately 7, indicating a neutral solution
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Worksheet
Presentation
Video
Lesson Details
Key learning points
- Neutralisation reactions involve an acid reacting with a base to form salt and water.
- Exothermic reactions release energy to the surroundings, often through heating.
- Methods must be detailed and replicable for reliable data collection.
- The initial and final temperatures of the reaction mixture need to be recorded to calculate energy change.
- Line graphs can illustrate relationships between continuous variables in experiments.
Common misconception
Pupils can assume that any decrease in temperature occurring when excess reactant is added to an exothermic reaction is because the reaction has become endothermic.
Explain that once the limiting reactant has been used up the exothermic reaction is complete. The addition of excess reactant will only act to cool down the reaction mixture.
Keywords
Neutralisation - Neutralisation is when a chemical reaction takes place between an acid and base to produce a neutral solution of a salt and water.
Exothermic - An exothermic reaction is a type of reaction in which energy is transferred from the reactants to the surroundings e.g. combustion.
Method - A method describes how an experiment is carried out; it is a step-by-step procedure.
Line graph - A line graph involves two continuous variables being plotted to show if a relationship exists between them. Any trends in the data are shown with the addition of a line of best fit.
Conclusion - A conclusion sums up what has been found out during an investigation. It always refers to both the independent and dependent variables.