This slide explores the use of models in science and the properties of the different states of matter (Solid, Liquid and Gas). It addresses year 7 syllabus content on matter and the particle model.

1. MODELS IN SCIENCE

2. WHY SCIENTISTS USE MODELS
● Scientists use their imagination to make models.
● A model is a way of showing and explaining something
we cannot easily see with our own eyes.
❖ Models can help us to understand the way particles are arranged,move
and behave in matter.
● Models help us explain our observations and can sometimes help us make
further predictions.
● One way to represent a model is in the form of a diagram.

3. The particle model theory of matter
❖ Scientists use a model to explain the different properties of
solids, liquids and gases.
❖ This model is called the particle model.

4. The particle model
A particle model of the different
states

5. The particle model
According to the particle model:
• all substances are made up of tiny particles
• the particles are attracted towards other surrounding
Particles
• the particles are always moving
• the hotter the substance is, the faster the particles

6. Properties of the
states of matter

7. Particles in Gases
● The forces between the particles in a gas are very weak.
● The particles are in constant motion.
○ This means that gases have no fixed shape or volume.
There are large spaces between the particles.
○ The spaces allow the gas to be compressed.
○ A gas can flow and diffuse easily since its particles are always moving.
● Particles in a gas have much more energy than particles in a solid or liquid.
● They move around and collide with other particles and the walls of the container they
are in.

8. Particles in Solids
● Solids cannot be compressed because the particles inside them are held closely
together.
● There is no space between them.
● Bonds also hold the particles tightly together in a rigid crystal-like structure.
● This gives solids their fixed shape and constant volume.
● The particles in solids cannot move freely; they vibrate in a fixed position.
● This means that solids are unable to flow.

9. Particles in Liquids
● The particles in a liquid are close together, so there is no room for compression
between them.
● The particles are also held tightly by bonds, but not in the same rigid structure
as solids.
This gives liquids their fixed volume, but allows the particles to roll over each
other. This rolling allows liquids to flow.
● The movement of the particles explains why liquids take the shape of their
container.
● The particles roll over each other until they fill the bottom of the container