1. © 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 7G Particle model of solids, liquids and gases

2. © OUP: To be used solely in purchaser’s school or college What is the world made of? 7G Particle model of solids, liquids and gases

3. © OUP: To be used solely in purchaser’s school or college 7G What is the world made of? - Big questions

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

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

6. © OUP: To be used solely in purchaser’s school or college The following stages are in the wrong order. Put them in the right order and explain your answer. evidence theory observations conclusion data prediction Answer- prediction observations data evidence conclusion theory 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.

7. © OUP: To be used solely in purchaser’s school or college Solids, liquids and gases 7G Particle model of solids, liquids and gases

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

9. © OUP: To be used solely in purchaser’s school or college 7G Solids, liquids and gases - It’s a matter of fact!

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

11. © OUP: To be used solely in purchaser’s school or college 7G Solids, liquids and gases - In a state! solidliquidgas 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?

12. © OUP: To be used solely in purchaser’s school or college 7G Solids, liquids and gases - In a state! solidliquidgas 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.

13. © OUP: To be used solely in purchaser’s school or college 7G Solids, liquids and gases – What are they made of?

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

15. © OUP: To be used solely in purchaser’s school or college The particle model 7G Particle model of solids, liquids and gases

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

17. © OUP: To be used solely in purchaser’s school or college 7G The particle model - The necklace of Democritus 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?

18. © OUP: To be used solely in purchaser’s school or college 7G The particle model - The necklace of Democritus 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?

19. © OUP: To be used solely in purchaser’s school or college 7G The particle model - The necklace of Democritus 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!

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

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

22. © OUP: To be used solely in purchaser’s school or college The particle model of a solid 7G The particle model – Solids, liquids and gases

23. © OUP: To be used solely in purchaser’s school or college 7G The particle model – Solids, liquids and gases The particle model of a liquid

24. © OUP: To be used solely in purchaser’s school or college 7G The particle model – Solids, liquids and gases The particle model of a gas

25. © OUP: To be used solely in purchaser’s school or college 7G The particle model – Solids, liquids and gases 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

26. © OUP: To be used solely in purchaser’s school or college 7G The particle model – Changing state Water can be a solid, liquid or a gas. Its state depends on how much energy the water particles have. If enough energy is added to or removed from the particles a change of state can occur. ice water steam

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

28. © OUP: To be used solely in purchaser’s school or college 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 TRUE FALSE TRUE