Writing word equations and finding reaction patterns | 14-16 years

In this activity, students work individually, reading and interpreting text by looking for patterns. It provides an opportunity for students to:

• Use word and symbol equations to describe reactions.
• Use patterns in reactions to make predictions about other reactions.
• Represent chemical reactions by word equations.

The materials can be used for diagnosis (to identify students needing practice), as a remedial exercise or for summative assessment.

Learning objectives

Students will:

• Understand that chemical reactions may be described by word equations.
• Recognise that each type of chemical reaction has its own general word equation.
• Be able to use word equations to describe chemical reactions.

Sequence of activities

Introduction

1. Remind students of the term ‘word equation’.
2. Ask them to:
   • Write an explanation of ‘word equation’ on a mini whiteboard.
   • Reveal their answers simultaneously.
3. Go around the displayed answers and make a brief comment on each.
4. Explain that the purpose of the lesson is to check their ability to write word equations.

Completing word equations 1

1. Give each student the sheets ‘Word equations – information sheet’ and ‘Completing word equations 1’ to try.
2. Tell students not to write reasons for their answers, but to think about the reasons – select students to give their reasons at the end of the session.
3. Ask them to say what answers they are unsure about. Explain that there are a number of sheets that might help them with the parts they are finding difficult.

Practising word equations

Suggest that they read the ‘Word equations – information sheet’. If this is insufficient, tell them to chose one or more of the following sheets and go through the exercises:

• ‘Word equations – the reaction between acids and alkalis’
• ‘Word equations – the reaction between acids and metals’
• ‘Word equations – the reaction between acids and metal carbonates’
• ‘Word equations – displacement reactions’
• ’Word equations – synthesis reactions’

When they feel able, ask each student to write answers to the questions they had been unsure about in ‘Completing word equations 1’.

Completing word equations 2 and feedback

1. Go through the correct answers to ’Completing word equations 1’ with the class. Select students to give reasons for the answers.
2. Give out copies of ‘Completing word equations 2’ and ‘Writing word equations’. Ask students to answer the questions and include their reasons.
3. Require students to hand in this final sheet for checking. Comment as necessary.

Commentary

Students look at their own performance and identify their own weaknesses in a clear-cut way. They work through support material to suit their needs and then reassess their understanding. As students can see the standard they are aiming for and select their own means to achieve it, they are more likely to work with a positive attitude.

The final worksheets enable the teacher to be satisfied that students have reached an appropriate level and to give further support.

Where the materials are used as a remedial exercise or for summative assessment, teachers can have model answers available for students to check their own work.

Equipment

Each student requires a mini whiteboard.

Answers

Completing word equations 1

1. Potassium nitrate
2. Copper nitrate
3. Sulfuric acid
4. Calcium chloride
5. Magnesium chloride

The reaction between acids and alkalis

1. Potassium chloride; sodium nitrate
2. Potassium hydroxide

The reaction between acids and metals

1. Iron nitrate; zinc sulfate; magnesium chloride, magnesium nitrate
2. Calcium

The reaction between acids and metal carbonates

1. Copper chloride, copper sulfate; zinc chloride, zinc nitrate; iron nitrate, iron sulfate
2. Magnesium chloride

Displacement reactions

1. Iron
2. Zinc sulfate
3. Magnesium, copper
4. Copper sulfate
5. Zinc chloride, iron
6. Iron sulfate
7. Zinc, copper nitrate
8. Copper
9. Iron nitrate, copper

It may be worth pointing out that the order of the reactants or products in the equation is irrelevant.

Synthesis reactions

1. Sulfur, fluoride
2. Magnesium sulfide, magnesium chloride; iron flouride, iron chloride; zinc oxide, zinc sulfide, zinc fluoride; copper oxide, copper sulfide, copper chloride
3. Sodium iodide; nickel sulfide; calcium

Completing word equations 2

1. Sodium sulfate
2. Copper chloride
3. Hydrochloric acid
4. Zinc oxide
5. Calcium nitrate

Writing word equations

1. Acid and alkali, copper oxide + sulfuric acid → copper sulfate + water
2. Acid and metal, zinc + hydrochloric acid → zinc chloride + hydrogen
3. Synthesis, magnesium + chlorine → magnesium chloride
4. Displacement, copper + silver nitrate → copper nitrate + silver
5. Acid and metal carbonate, copper carbonate + sulfuric acid → copper sulfate + carbon dioxide + water