7g particles

© OUP: To be used solely in purchaser’s school or college

7G Particle model of solids, liquids and gases

What is the world made of?

Solids, liquids and gases

The particle model



What is the world made of?



7G What is the world made of? - Big questions


7G What is the world made of? - Ancient thinkers

Greek thinkers thought everything was made up of 4 things:

Since ancient times the greatest thinkers have tried to understand and group the world around them.


7G What is the world made of? - Ancient thinkers

The ancient Chinese had a slightly different view. They believed the universe was made up of 5 components:

In India they added a fifth group:


The following stages are in the wrong order.Put them in the right order and explain your answer.

evidencetheory

observationsconclusion

dataprediction

Answer-

predictionobservations

dataevidence

conclusiontheory

7G What is the world made of? - Creating a theory

A theory is an idea that explains observations.

Scientists, like ancient thinkers, are curious about the world. They carry out investigations and produce theories about what they see.

But a theory doesn’t just appear by itself!Creating a good theory involves several stages.


Solids, liquids and gases



7G Solids, liquids and gases - It’s a matter of fact!

There are 3 states of matter…

Matter is all the stuff around you – everything you can touch, see or smell.

Everything in the Universe is made of matter.


7G Solids, liquids and gases - It’s a matter of fact!


7G Solids, liquids and gases - In a state!

You can investigate solids, liquids and gases to understand how they behave.

A useful starting point is to think about their shape and volume.



solid liquid gas

fixed shape

fixed volume

Fill in the table with the answers to these testing questions:

Does it have a fixed shape?Does it have a fixed volume?



solid liquid gas

Is it easy to squash?

Does it conduct heat well?

Can it spread out?

Can it stretch?

Is it heavy for its size?

Now answer some more testing questions about a solid, a liquid and a gas.


7G Solids, liquids and gases – What are they made of?


7G Solids, liquids and gases – What are they made of?

You can do the same “splitting experiment” if you think about a liquid or a gas.

Solids, liquids and gases are all made of tiny particles. This is called the particle theory.


The particle model



7G The particle model - The necklace of Democritus

Democritus, an ancient Greek thinker, was one of the first to suggest the idea of particles.

He also thought about the size of these particles.

Democritus considered the particles in a grain of salt (one millimetre cubed).



Imagine you could take apart all the particles in this grain of salt.

Next you arrange all the particles in a row.

How long would the row of particle be?

Would it be long enough to make a necklace?



Democritus never found out the answer to his salty puzzle. Thousands of years later, we know just how long the row of salt particles would be…

That’s more than 33 times the distance from the Earth to the Moon!

12 900 000 000 metres

All that from just one grain of salt!

What does tell us about the number and size of the particles?



The number of particles is very, very, very, very, very, very, very, very, very, very ,very, very big!

So next time you pour salt on your chips spare a thought for all those tiny salt particles!

The size of the particles must be very, very, very, very, very, very, very, very, very, very, very small!


7G The particle model - From theory to model

Any theory about particles must be able to explain the differences between a solid, a liquid and a gas.

Solids, liquids and gases behave in different ways.

What does this tell us about their particles?

A theory is an idea that explains observations.

Scientists use a model to give a mental picture of what is happening in their investigation.


7G The particle model – Solids, liquids and gases

The particle model of matter describes:

how particles are arranged

how much energy particles have and how they move

In some matter the particles are held together by forces of attraction.

Use the particle model to decide if the forces of attraction are strong, weak or do not exist.


The particle model of a solid




The particle model of a liquid



The particle model of a gas



solid particles…- are very close together in a fixed arrangement - have a small amount of energy- vibrate but do not move

liquid particles…- are close together but have no fixed arrangement - more energy than solid particles- vibrate and can move about

gas particles- are far apart and have no fixed arrangement- have a large amount of energy- move rapidly in all directions


7G The particle model – Changing state

Water can be a solid, liquid or a gas.

Its state depends on how much energythe water particles have.

If enough energy is added to or removed from the particles a change of state can occur.

ice water steam


7G The particle model – Changing state

Match the change of state to the correct arrow on the diagram.

freezing condensing melting evaporating

What happens to the particles during each change of state?

CLUE: Think about their energy, their movement and the distance between them.

ice water steam


7G The particle model – True or false?

True or False? 1. The particles in gas have a large amount of energy. 2. The particles in a solid have no forces of attraction between them. 3. The particles in a liquid are close together and have a fixed

arrangement. 4. When a liquid freezes it becomes a gas. 5. Evaporation describes the change from a liquid to a gas. 6. When a liquid loses energy it becomes a gas. 7. A gas condenses to a liquid when its particles lose energy. 8. When the particles in a solid gain energy the solid melts.

TRUE

FALSE

FALSE

FALSE

TRUE

FALSE

TRUE

TRUE

7g particles

Documents