GCSE Physics

1. GCSE Physics Solids, liquids and gases

2. Lesson 4 – The structure of matter • Aims: • To understand that a substance can change state from solid to liquid by the process of melting • To understand that a substance can change state from liquid to gas by the process of evaporation or boiling • To recall that particles in a liquid have a random motion within a close-packed structure • To recall that particles in a solid vibrate about fixed positions within a close-packed regular structure

3. What are the three states of matter? liquid gas solid

4. Solids • Definite shape, • Definite volume, • Particles close together, fixed, • Particles move relatively slowly.

6. Liquids • No definite shape, definite volume, • Take the shape of container, • Particles are close together, but mobile • Particles move a little quicker.

7. Mercury • Mercury is the only metallic element that is a liquid at room temperature. • It is more than 13 times heavier than water.

8. Gases • No definite shape • No definite volume • Take the shape and volume of container • Particles are far apart • Particles move fast

10. Comparing states

11. Comparing states

12. Comparing states

13. Comparing states

14. Comparing states

15. 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 - have 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

16. Changing state

17. Changing states of matter COLD WARM HOT Solids can turn into liquids, and liquids can turn into gasses and back again - depending on the temperature. So, we can use the effect of heat on states of matter to measure the temperature of something.

18. Condense Freeze Boil Melt Gas Liquid Solid

19. Changing state is a physical change.

20. Sublimation Vaporization Condensation Melting Solid Gas Liquid Freezing Condensation

21. Sublimation • Sublimation is the physical changing of a solid into a gas. • Only a very few substances change from a solid to a gas without becoming a liquid. • Carbon dioxide is an example of a compound that sublimes.

22. Changing state graphs

23. Heating Curve for Water 120 Steam Water and Steam 100 80 60 Water 40 20 Water and Ice 0 Ice -20 40 120 0 220 760 800 Temperature (degrees Celsius) Time in seconds

24. Energy is transferred when something changes state.

25. Heating Curve for Water 120 Steam Water and Steam 100 80 60 Water 40 20 Water and Ice 0 Ice -20 40 120 0 220 760 800 Temperature (degrees Celsius) Time in seconds

26. Liquid to a gas • At its boiling point water changes state from a liquid into a gas. • Energy must be transferred to the water so that it’s molecules can change from a liquid to a gas.

27. Heating Curve for Water 120 Steam Water and Steam 100 80 60 Water 40 20 Water and Ice 0 Ice -20 40 120 0 220 760 800 Temperature (degrees Celsius) Time in seconds

28. Ice to water • When an ice cube at zero Celsius is left on a table on a warm day it will melt. • Energy from the room is transferred to the ice cube to change it from a solid to a liquid. • When all of the ice has melted the water will start to increase in temperature towards that of the room.

29. Water to ice • Place water into an ice cube tray and then place it into a freezer. • The water in the tray is hotter than the freezer. As energy is transferred from the water to the freezer the temperature drops. • At zero degrees Celsius the water keeps transferring energy to the freezer but does not get colder. Instead the water changes state from a liquid to a solid. • When all of the water has turned to ice it will again start to fall in temperature until it has the same temperature as the freezer compartment.

30. Two states at the same temperature

31. Heating Curve for Water 120 Steam Water and Steam 100 80 60 Water 40 20 Water and Ice 0 Ice -20 40 120 0 220 760 800 Both Water and Steam Temperature (degrees Celsius) Time in seconds

32. At 100 degrees Celsius water and steam can both occur

33. Heating Curve for Water 120 Steam Water and Steam 100 80 60 Water 40 20 Water and Ice 0 Ice -20 40 120 0 220 760 800 Temperature (degrees Celsius) Ice and Water Time in seconds

34. At zero degrees Celsius both ice and water can both occur.

35. Heating Curve for Water 120 Steam Water and Steam 100 80 60 Water 40 20 Water and Ice 0 Ice -20 40 120 0 220 760 800 Temperature (degrees Celsius) Time in seconds

36. Summary – The structure of matter • A substance can change state from solid to liquid by the process of melting • A substance can change state from liquid to gas by the process of evaporation or boiling • Particles in a liquid have a random motion within a close-packed structure • Particles in a solid vibrate about fixed positions within a close-packed regular structure

37. The three states of matter are . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . and . . . . . . . . . . . . . . . . . . . All matter consists of tiny . . . . . . . . . . . . . . . . . . travelling at . . . . . . . . . . . . . speed.

38. A solid has a definite size and a definite . . . . . . . . . . . . . . . . . . because the forces between its . . . . . . . . . . . . . . . . . . are very . . . . . . . . . . . . . . . . . . . A liquid has weaker forces between its . . . . . . . . . . . . . . . . . . and so does not have a definite . . . . . . . . . . . . . . . . . . .

39. If a substance is cooled down, its molecules move at a . . . . . . . . . . . . . . . . . . speed. When some molecules pass through some other molecules, we call it . . . . . . . . . . . . .    The twisting and jerking of smoke particles when they are hit by air . . . . . . . . . . . . . . . . . . is called . . . . . . . . . . . . . . . . . . .

40. Evaporation and Boiling

41. Evaporation

42. Evaporation Liquid cools because it loses higher energy molecules or atoms Air cools because the molecules leaving give up a lot of energy to break free, so they have much lower energy after they gain their freedom

43. Evaporation from liquids takes place at all temperatures; • it occurs when particles at the surface gain enough energy to move away from the attractive forces of neighbouring particles..

44. How to make a liquid evaporate more quickly? • Increase the temperature • Increase the surface area • Reduce the humidity • Blow air across the surface

45. Boiling

46. Boiling Molecules break free of the liquid bonds and form little bubbles If the vapor pressure in the bubble is large enough to resist the pressure of the liquid, and the air pressure above the interface they rise and escape to the outside Remember, liquid is cooling and air is cooling

47. Boiling in a liquid only takes place at the boiling point; when a liquid boils, bubbles of vapour form in the body of liquid and rise to the surface, where they collapse and release the vapour into the atmosphere

48. Changing the boiling point • Impurities Impurities raise the boiling point of water. • Pressure Reduce the pressure lowers the boiling point.

49. Pressure cooker P≈2P0, boiling point at about 120℃

50. When will these phenomenon occur? What will happen during and after these phenomenon? rapid ,gas bubbles are produced throughout. slow; occurs at the surface.