Teaching sequence

Lesson objective

Students recognise that not all substances can be easily classified based on their observable properties.

Introduction

Organise students into cooperative learning teams and provide each team with a plastic plate. Squirt some hair mousse on to the plate and ask the students to classify it as a solid, a liquid or a gas. Ask them to also predict what they think will happen to the hair mousse over time and why they think this might happen. Does this impact on their classification?

Put the plates of hair mousse to the side of the class during the lesson and remind students to visit their plate of mousse at regular intervals during this time to make further observations.

Core

1. Discuss the students’ present understanding of the properties of solids, liquids and gases.
2. Provide each learning team with samples of the following substances:
   • jelly crystals and jelly
   • salt or sugar
   • Blu-tack® (or similar).
3. Ask students to use the information they have learnt about the observable properties of different materials to decide whether or not these substances are a solid, liquid or gas. Ask them to explain their thinking.
4. Provide each team with a copy of the worksheet Making slime (Word, 392 KB) and the materials and equipment necessary to complete the activity. Once they have made their slime allow them to time to investigate its properties and try to determine whether or not it is a solid, liquid or gas.
   Teacher note: This activity can get messy so you may prefer to do it outside under a covered area.
5. As a class, view the video Mythbusters: walking on ‘water’. Discuss with the students what they saw. Ask them how the cornflour and water mixture behaved when placed under pressure.

Conclusion

Ask students to share their thoughts on the classification of the substances they used during the lesson. How easy were they to classify? What made it difficult?

Have students choose a substance and develop a short presentation on how it would be best classified and why.