Solids, liquids and gases

States of matter

Different substances What are the substances described in the table? (Clue: the first letters spell out another word for ‘substance’.) Description Substance liquid metal mercury solid used in aircraft aluminium solid used to coat steel cans tin intoxicating liquid ethanol radioactive solid radium solid that rusts iron unreactive gas argon solid used by Roman plumbers lead

Three states of matter At room temperature all substances exist in one of three physical states. solid liquid gas

Solid, liquid or gas?

The particle model

The particle model The difference between solids, liquids and gases can be explained by the particle model. All substances are made up of particles. The particles are attracted to each other. Some particles are attracted strongly to each other and others weakly. The particles move around. They are described as having kinetic energy. The kinetic energy of the particles increases with temperature.

Particles in action

Solids, liquids and gases

What are the properties of solids? A solid: has a high density as the particles are very close together cannot be compressed as there is very little empty space between particles has a fixed shape as the particles are held together tightly cannot diffuse as the particles are not able to move does not exert any pressure as the particles cannot move around.

What are the properties of liquids? A liquid: has a fairly high density as the particles are close together cannot be compressed as there is very little empty space between particles takes up the shape of its container as the particles can move can diffuse as the particles are able to change places can exert some pressure as the particles are able to move and hit the sides of the container.

What are the properties of gases A gas: has a low density as the particles are far apart can be compressed as there is space between particles has no fixed shape as the particles move about rapidly in all directions can diffuse as the particles are able to move in all directions can exert a lot of pressure as the particles are able to move in all directions and hit the sides of the container.

Solids, liquids and gases: which one?

Diffusion

How do smells spread out? Where is the smell coming from and how does it spread out?

What is diffusion? Diffusion is the random movement of particles that causes them to spread out and mix with other particles. For example, the smell of aftershave or perfume diffuses and is detected by people on the other side of a room. Use the particle model to explain these facts about diffusion: Diffusion happens more quickly at high temperatures than at low temperatures. Diffusion occurs in liquids and gases, but hardly at all in solids. Diffusion happens more quickly for gases than for liquids. Photo credit: Gaston Thauvin

Diffusion in action: one gas

Diffusion in action: two gases

Rate of diffusion In this experiment, two gases diffuse towards each other in a sealed glass tube. cotton wool soaked in ammonia gases meet here cotton wool soaked in hydrochloric acid solution When the gases meet, they react and form a ring of ammonium chloride, which is closer to one end of the tube than the other. Which gas particles diffuse faster? The ammonia particles have travelled further down the tube so they must have diffused at a faster speed.

Summary activities

Glossary diffusion – The process in which particles randomly move and spread out in gases and liquids. gas – The state of matter in which particles can freely move, and in which substances have no fixed volume or shape. liquid – The state of matter in which particles are close together but free to move, and in which substances have a fixed volume and assume the shape of their container. matter – The stuff that everything is made of. particle – The smallest unit of matter. pressure – The force produced when particles move against a surface. solid – The state of matter in which particles are close together and cannot move, and in which substances have a fixed shape and volume.

Anagrams

Multiple-choice quiz