Science at key stage 3 (Year 7)
Unit 7E: Acids and alkalis
Section 2: b. What are acids and alkalis like and where do we use them?
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Objectives |
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- to recognise and interpret common hazard signs
- to select key ideas from written material
- how to deal with acids or alkalis if they are spilt or splashed on the skin
- that adding water to an acid or alkali solution dilutes it and makes it less hazardous
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Activities |
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Outcomes |
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Children: |
- Provide pupils with containers for household and laboratory acids and alkalis with hazard warning labels, student safety sheets, Hazcards and information about hazard symbols and ask them to describe the distinctions between them and why the materials they used in the previous activity did not have hazard labels. Ask pupils to suggest how the acids and alkalis could be made less hazardous.
- Consider hazard warning signs used when acids and alkalis are transported by road.
- Ask pupils to suggest why different acids and alkalis are labelled differently and to suggest safety procedures for working with acids and alkalis. Agree a common set of procedures, which should include use of eye protection.
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- identify hazard symbols for harmful, irritant and corrosive substances
- describe how to work safely with acids and alkalis and what to do if a spill occurs
- explain that if water is added to an acid or alkali it dilutes it and the solution becomes less hazardous
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Points to note |
- In the next activity, acids are distinguished from alkalis using indicators.
- CLEAPSS produces Hazcards and student safety sheets.
- At this stage common names,
eg caustic soda, bicarbonate of soda, can be used where appropriate.
- Adding water to concentrated sulphuric acid is hazardous because the reaction is highly exothermic. Concentrated sulphuric acid should be diluted by adding the acid to water.
- It may be helpful to point out that sulfur is the internationally accepted spelling.
Safety
- containers should be sealed or empty
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This unit is divided into sections. Each section contains a sequence of
activities with related objectives and outcomes. You can view this unit by
moving through the sections or print/download the whole unit.
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