Reactions of acids with metals and carbonates | 11-14 years

A series of statements about acids and their reactions with metals and carbonates help students focus as they think about and discuss these reactions.

This exercise is designed to check on the following misconceptions:

• Acids release carbon dioxide which was previously locked up inside a carbonate.
• Metals are eaten up by acids and simply vanish.
• All gases behave in the same way.
• All chemical reactions produce a gas.
• An observed ‘fizz’ is not associated with the release of a gas in a solution.

Learning objectives

Students will understand:

• How acids react with metals and carbonates.

Sequence of activities

Demonstration and introduction

1. Place two Petri dishes containing dilute sulfuric acid on an OHP.
2. Add a small piece of magnesium ribbon to one dish and a small amount of copper(II) carbonate to the other dish.
3. Ask several students to describe what they see. (Alternatively, use a video camera or flexible necked camera connected to a data projector.)
4. Share the learning objective for the session.

Initial self-assessment

Give each student an ’Activity sheet’ and a ’Response sheet’. Ask them to:

• Quickly assess how well they understand what happens when acids react with metals.
• Tick the appropriate traffic light box on the ’Activity sheet’.

Statements activity: stage 1

1. Put students into groups of three on the basis of their traffic light choices so that each group has a mix of greens, yellows and reds.
2. Give each group 10 ’Statement cards’.
3. Circulate and support with prompts while students:
   • In their groups, place each card into one of the following categories:
     • ‘Statements that we think are true’
     • ‘Statements that we think are not true’
     • ‘Statements that we are not sure about’
   • Individually tick boxes on their copy of the ‘Response sheet’ to show which category they have agreed to put each statement into
   • Write down why they think specific statements are not true.

Statements activity: stage 2

1. Arrange students into new groups of three so that each member of a new group comes from a different initial group.
2. Circulate and support with prompts while the new groups:
   • Compare their judgements about which category to place each statement in.
   • Write on their ’Response sheet’ any ideas that they think they should take back to their original group.

Statements activity: stage 3

1. Ask students to return to their original groups.
2. Circulate while students:
   • Talk about ideas they have brought back from other groups.
   • Decide if they want to change the category of any of the statements.

Plenary

1. Bring all students into a plenary.
2. Ask specific students to:
   • Feedback about some of their group’s decisions.
   • Report whether they changed their mind during the lesson.
   • Explain why they changed their ideas.
3. Focus particularly on statements that will make the following misconceptions explicit:
   • ‘Acids let carbon dioxide escape from inside a carbonate.’
   • ’When a metal reacts it vanishes.’
   • ‘Hydrogen and carbon dioxide are both gases so they have the same properties.’

Concluding self-assessment

Ask students to:

• Complete the second group of traffic light boxes on their ’Activity sheet’.
• Identify aspects that they are still uncertain about.
• Hand in their ’Activity sheets’.

Feedback

Write on the ’Activity sheets’ what the student should do to clarify points that they are still uncertain about.

Practical notes

Equipment

• Petri dishes x2
• Dilute sulfuric acid (HARMFUL)
• A small piece of magnesium ribbon (FLAMMABLE)
• A small amount of copper(II) carbonate (HARMFUL)

Health, safety and technical notes

• Read our standard health and safety guidance.
• It is the responsibility of the teacher to carry out an appropriate risk assessment for the demonstration.

Commentary

The initial demonstration enlivens the introduction of the learning objective.

Using ‘traffic lights’ assists with setting up mixed groups and gives students a starting point. The statement cards encourage students to talk about these chemical reactions and encounter a wider range of ideas by moving between different groups. By confronting and assessing the misconceptions, they then focus more sharply on the correct messages that are an essential part of the plenary. Students’ confidence in assessing themselves grows as a result of actively comparing their understanding at the start of an activity with that at the end.

Written feedback should help students to see what further work they need to do.