Lesson Plan

3. Outline neutralisation reactions

KS3-15-03

Intent

Learning Intention

  • Define neutralisation and identify when a chemical reaction involves neutralisation
  • Identify the pH scale and understand how it relates to acidity and basicity
  • Develop problem-solving skills related to neutralisation; apply knowledge of neutralisation to solve problems related to chemical reactions involving acids and bases

National Curriculum

  • Learn about pH and how it is measured
  • Understand that reactions can neutralise each other
  • Understand that solutions that contain excess hydroxide ions (alkalis) or hydrogen ions (acids) can be identified using indicators

Working Scientifically

  • Select, plan and carry out the most appropriate types of scientific enquiry to test predictions, including identifying independent, dependent and control variables 
  • Use appropriate techniques, apparatus, and materials during fieldwork and laboratory work, paying attention to health and safety

Learning Outcomes

  • Understand the concept of neutralisation reactions
  • Define acid, base and neutral solutions
  • Carry out a simple experiment to compare the effectiveness of two indigestion remedies in neutralising stomach acid

Resources

Resources: Hydrochloric acid, universal indicator solution, indigestion remedies A and B, syringe, beaker, white tile, safety goggles and lab coats. 

Core Handout: An investigation sheet to accompany the indigestion remedies activity. 

 

Rocket words

  • neutralisation
  • base
  • heartburn
  • hydroxide
  • antacid

Implementation

Prior Learning 

Use the previous lesson to refresh the students’ understanding of acids and bases, including their properties and examples of each.

Starter

Recap the previous lesson on acids and bases, focusing on the properties of acids and bases and the pH scale. Ask students to identify and write down the definition of a neutral solution. Review the concept of neutralisation reactions and how they occur.

Main Teaching

Introduce the concept of neutralisation reactions and explain how they occur. Provide examples of neutralisation reactions, including the reaction of an acid with a base to produce a salt and water. Demonstrate the experiment to compare the effectiveness of two indigestion remedies in neutralising stomach acid, step by step. Explain how the universal indicator works and how it can be used to determine the pH of a solution. Allow the students to work in pairs to carry out the experiment using the two indigestion remedies provided, and record their observations and results. Discuss the results and explain how the effectiveness of the indigestion remedies can be compared based on the amount needed to neutralise the acid. Reinforce the importance of safety precautions when working with chemicals.

Career Film: Andrew is a Natural Gas Trade Analyst for BP.

Expert Film: Dr Sam Rowe demonstrates the use of universal indicator solution during a neutralisation reaction.

Mission Assignment

Indigestion Remedies

The students will be comparing two unknown indigestion remedies to determine which is more effective at neutralising "stomach acid".

Student Method

  1. Place 10 ml of hydrochloric acid in a beaker and add a few drops of universal indicator solution (it should turn red). Place the beaker on a white tile so that the colour can be seen clearly.
  2. Fill a syringe of remedy A. Slowly add this to the beaker. While adding, gently swirl the beaker to ensure the two solutions are mixed. Continue slowly adding the solution until the indicator shows a neutral solution (green).
  3. Record the amount of remedy that was added to the solution to neutralise it.
  4. Repeat this process for remedy B.

It is a good idea to do multiple trials with the first remedy to give a rough idea of the neutralisation point. This then enables subsidiary trials to be done more precisely.

Balancing Chemical Reactions

On the handout, the students can balance the neutralisation chemical reactions.

Differentiated tasks (Support/Challenge)

Support: 

  • Simplify the language used when explaining the concept of neutralisation reactions.
  • Provide step-by-step guidance when carrying out the experiment, including the use of the syringe and universal indicator solution.
  • Use visuals such as pictures and diagrams to help illustrate the topic.
  • Provide extra time for students to complete their work and ask questions. 

Stretch: 

  • Provide a clear explanation of the concept of neutralisation reactions and how they occur.
  • Use practical demonstrations and examples to help reinforce the topic.
  • Challenge students to predict the results of the experiment before carrying it out.
  • Encourage students to work in pairs or small groups to discuss and explain the concept of neutralisation reactions and their applications.
  • Provide extra challenge questions for students who demonstrate a good understanding of the topic.

Challenge: 

  • Provide a more in-depth explanation of the topic, including the scientific principles behind neutralisation reactions.
  • Encourage students to explore the topic further by researching and presenting on a specific aspect of neutralisation reactions and their applications.
  • Provide opportunities for students to design their own experiments related to neutralisation reactions and to explain their methodology and results.
  • Encourage independent thinking and critical analysis through open-ended questions and discussions.

Impact & Assessment Opportunities

Plenary

Ask the students to share their observations and results from the experiment. Review the learning objectives and ask students to reflect on whether they have achieved them. Preview the next lesson on chemical reactions, which will build on the concepts learned in this lesson. 

Teacher Mastery

Bases are defined as substances which can react with acids and neutralise them. Many bases are insoluble and do not dissolve in water. If a base does dissolve in water then it is defined as an alkali.

The reaction between an acid and an alkali is known as a neutralisation reaction. If the correct amount of an acid and an alkali are added together then this will produce a neutral solution. The reaction will be exothermic meaning that energy will be given out to the surroundings. The surroundings will then have more energy and the temperature will increase. Common laboratory acids are: hydrochloric acid, sulphuric acid and nitric acid. Common alkalis are metal oxides (e.g. copper oxide, CuO), metal hydroxides (e.g. sodium hydroxide, NaOH) and metal carbonates (e.g. potassium carbonate, K₂CO₃). It is important to remember that the reaction of an acid with a metal carbonate produces carbon dioxide gas (CO₂) in addition to salt and water.

Salts produced from the reactions of acids and alkalis are named in the following way: the first part of the name derives from the alkali (i.e. the metal within the metal oxide, metal hydroxide or metal carbonate) that was used and the second part of the name derives from the acid that was used. Salts derived from hydrochloric acid have chloride as the second part of their name, salts derived from sulphuric acid (H₂SO₄) have sulphate as the second part of their name and salts derived from nitric acid (HNO₃) have nitrate as the second part of their name. 

Other, less common, acids could also be included in the discussion. For example, salts derived from hydrobromic acid (HBr) have bromide as the second part of their name and salts derived from phosphoric acid (H₃PO₄) have phosphate as the second part of their name.