1. Science 8: Unit A – Mix and Flow of Matter
Topic 1: Matter on the Move

2. What is a Fluid?
A fluid is a substance which flows. This means that liquids and gases are both considered fluids, while solids are not.
Solids that are made up of small particles (like salt crystals) can appear to be fluids. They ‘flow’ when you are pouring it out a box. However a fluid will always flow so that it’s flat along a surface, a solid when it’s poured will form a pile.
So a defining characteristic of fluids is that they flow, usually from an area where there are more particles (higher concentration) to an area of few particles (lower concentration). Remember this? It’s called diffusion.

3. Three States of Matter
1. Solid – the state of matter where the substance has a definite shape and volume.
2. Liquid – a fluid state of matter where the substance has a definite volume, but takes the shape of its container.
3. Gas – a fluid state of matter where the substance does not have a definite shape, but takes the shape of its container. Also, a gas does not have a definite volume, but fills up any container it is in.

4. Particle Model of Matter
All substances are made up of tiny particles. There are five rules that apply to all substances and the particles that make them up.

5. Particle Model of Matter – Rule #1
1. All substances are made up of tiny particles.

6. Particle Model of Matter – Rule 2
2. All particles in a pure substance are the same. Different pure substances are made up of different particles.

7. Particle Model of Matter – Rule 3
3. The particles have spaces between them.

8. Particle Model of Matter – Rule 4
4. The particles are always moving. Particles in solids vibrate, in liquids they slide around each other, and in gases they bounce around freely.
b) The speed of the particles increases when their temperature increases, and the speed decreases when the temperature decreases. All particles stop moving at ABSOLUTE ZERO: - 273ºC. At this temperature everything, including all gases, freeze, and turn to solids.

9. Particle Model of Matter – Rule 5
5. The particles in a substance are attracted to one another. Different kinds of particles are more strongly attracted to each other than others.

10. Changes of State