How can materials change?

Preparation

Previously, pupils should have used their senses to examine different types of materials. They should have made observations about the texture, shape, size, appearance, smell or colour of materials, and compared different materials to find similarities and differences.

Collect the following materials required by the investigation worksheet: salt, liquid starch, water, tempera paint or food colouring, containers or bowls, spoons, paintbrushes, art paper.

Curriculum links

Uses of everyday materials

• Find out how the shapes of solid objects made from some materials can be changed by squashing, bending, twisting and stretching.

Suggested teaching strategies

• Create a schema map using the lesson heading to identify prior knowledge, misconceptions and record new learning at the end of each lesson. A common misconception would be that physical changes cannot be ‘undone’.
• Construct a vocabulary wall to collect and display vocabulary throughout the unit.

Introduction

Stretching, twisting, squashing and bending materials (such as playdough) can be a good introduction activity for this lesson.

Display the digital lesson on your smartboard to introduce how materials can change.

Explain to pupils that not all materials change shape, size, colour or temperature. Some may change in one way and others may change in many ways. Ask pupils to give examples of materials that can be melted, cut, mixed, frozen, dissolved, boiled or moulded but which basically remain the same. List these in categories on the board if desired.

The summary and worksheet should be used together.

Development

Provide pupils with the summary and worksheet to complete.

To answer the questions on the worksheet, pupils are only thinking about physical changes to materials. Ensure that their answers are based on the text information. When deciding which materials to write about to answer Question 3(b), pupils could use the pictures on the summary to answer the question. If suggesting other materials not included on the summary, they must remember the two main aspects of physical change: the material basically remains the same/no new material is created AND the change can be reversed. An example of an irreversible change is wood when burnt, which undergoes a chemical change rather than a physical change. However, wood cut into pieces or painted undergoes a physical change.

Differentiation

• Provide additional examples of materials changing to support students requiring visual prompts.
• As an extension to this lesson, students can formulate ‘what would happen if… ?’ questions about materials, make a prediction and use books or websites to research their question with a partner.

Conclusion

Display the students’ paintings in the class and discuss their answers to the investigation worksheet.

Assessment

Worksheet answers
1. Answers will vary but will include four from the following list: wood, air, cement, plastic, rubber, cotton, paper and metal.
2. All boxes should be ticked.
3. (a) size, colour (b) playdough, paper, hot plate/element, water
4. (a) True (b) True

Investigation worksheet answers
1.–3. Teacher check
4. The salt dissolved/mixed in with the other ingredients.
5. Teacher check
6. Salt appeared and created a sparkly effect when the liquid dried. (It should be easily visible.)