Science at key stage 3 (Year 7)

Unit 7G: Particle model of solids, liquids and gases
Section 1: How can we explain evidence from experiments?

Objectives

Children should learn:

to classify materials as solid, liquid or gas
to use their existing knowledge and understanding to interpret and explain results
to work together, listening to and evaluating the contributions of others
that discussion can help clarify ideas

Activities		Outcomes
		Children:
Check that pupils are familiar with the terms 'solid', 'liquid' and 'gas' and have some understanding of what these mean. Present them with examples and ask them to allocate each example to the appropriate class. Introduce the idea that pupils will work in groups to carry out some quick experiments which will help them explain why solids, liquids and gases behave differently, eg comparing the masses of identically-sized blocks of two or three different materials such as wood, glass and metal putting one small coloured crystal into a beaker of cold water and one into a beaker of hot water trying to fit a metal bar into a gauge before and after strong heating opening a perfume bottle at arm's length heating one end of a metal rod that has paperclips attached by petroleum jelly trying to depress the plungers of three sealed syringes, one containing a solid, one a liquid and one a gas adding small weights, one at a time, to a thin wire suspended from a clamp until it snaps Ask pupils to discuss with others what they observe and try to explain what has happened. If pupils cannot give any explanations to start with, it may be helpful to suggest that they try to imagine they can see what is happening through powerful microscopes. Ask groups of pupils to present observations and to describe and explain them, eg through oral, flip-chart or overhead-projector (OHP) presentation. Discuss different ideas with pupils and ask them to compare their own ideas with those of others.		classify materials as solid, liquid or gas offer explanations (which may be incorrect) in which they try to link their existing knowledge to observations, eg the syringe which contains a solid won't squash because it's got no air in it the metal rod expands because the particles get bigger evaluate their own explanations and those given by others

Points to note

These activities should be carried out quickly. Their purpose is to encourage pupils to look for and give explanations for their observations. Most pupils will have incorrect ideas at this stage. They should be encouraged to evaluate them and compare them with those of others. They will be introduced to accepted explanations later in the unit.
It may be helpful to have key phrases prepared for pupils to use.
This work links to unit 7A(ii) 'Understanding materials (resistant materials)' in the design and technology scheme of work.

Safety

use of the Bunsen burner is introduced in unit 7I 'Energy resources'. If pupils have not done this unit, they will need to be shown how to use a Bunsen burner
handle crystals with forceps
remind pupils that some things remain hot even if they do not look hot
take care with sharp edges on glass or metal blocks
use eye protection when adding weights to a thin wire and make sure feet are well out of the way of falling weights
make sure pupils know what to do if something catches fire

Sections in this unit

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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.


	1. How can we explain evidence from experiments?
	2. How are theories created?
	3. What are the differences between solids, liquids and gases?
	4. How can the particle model explain the differences between solids, liquids and gases?
	5. a. How can the particle model explain other phenomena?
	6. b. How can the particle model explain other phenomena?
	7. Reviewing work

Science at key stage 3 (Year 7)

Objectives

Activities

Outcomes

Points to note

Sections in this unit