1. Mrs Teo Chin Chew The Chinese High School

2. Changes in State MeltingMelting FreezingFreezing BoilingBoiling CondensationCondensation SublimationSublimation

3. Changes in State of Matter SOLID LIQUID GAS boiling or evaporation condensation melting freezing Sublimation

4. Changes in State Changes in the state of matter can be explained by the kinetic theory of matter. The kinetic theory of matter states that matter is made up of particles which are in a state of continuous, random motion.

5. When solid is heated particles gain energy vibration of particles increases => kinetic energy increases => temperature rises eventually particles able to overcome the forces that hold them together, move past one another instead of just vibrate => changes from a solid state to a liquid state -melting -temperature at which this occurs is called the melting point temperature remains constant during melting Changes in State Melting

6. Changes in State Changes in State Time from start/mins Temp / 0 C A BC D

7. Changes in State Changes in State Time from start/mins Temp / 0 C A BC D m.p. 69 0 C solid mixture of solid and liquid liquid

8. Changes in State Changes in State When a liquid is cooled particles lose energy to the surroundings particles slow down => and eventually particles take up fixed and orderly positions as in a solid => changes from a liquid state to a solid state - freezing - temperature at which this occurs is called the freezing point temperature remains constant during freezing Freezing

9. Changes in State Changes in State When a liquid is heated particles gain energy particles move more quickly => kinetic energy increases => temperature rises eventually overcome the forces of attraction and are able to move freely and far apart => changes from liquid state to gaseous state - boiling -temperature at which this occur is called boiling point temperature remains constant while liquid boils Boiling

10. Changes in State Changes in State Temp / 0 C Time from the star A B C Temp / 0 C Time from the start/mins A

11. Changes in State Changes in State 74 0 C Temp / 0 C Time from the start/mins A B mixture of liquid and gas liquid C

12. What is the effect of pressure on boiling point? (a) boiling point? melting point? ( b) melting point?

13. Effect of Pressure on Boiling and Melting Points 1. The boiling point of a liquid increases as the pressure acting on it increases. 2.The melting point of a solid decreases as the pressure acting on it increases.

14. Application of Increased Pressure Application of Increased Pressure The Pressure Cooker 1. Lid tightly fastened to the pan 2. Rubber sealing ring prevents steam from escaping 3. Pressure of steam builds up. B.p. of water rises to 120 O 4. The control valve. If pressure too high, it lifts the weight, some steam escapes and the weight falls back into position

15. Changes in State Changes in State Evaporation liquid turning into gas without boiling -occurs below boiling point liquid turning into gas without boiling -occurs below boiling point particles escape from the surface of the water particles escape from the surface of the water

16. Changes in State Differences between evaporation and boiling EvaporationBoiling 1. occurs only at surface occurs throughout of liquid the liquid 2. takes place slowly takes place quickly occurs only at below boiling point boiling point 3.occurs at temperatures occurs only at below boiling point boiling point

17. Changes in State Changes in State Condensation gas is cooled to become liquid heat energy is given out takes place over a range of temperature cooled

18. Changes in State Changes in State - solid changes to vapour without going through the liquid state Sublimation e.g. dry ice (solid carbon dioxide) - solid below - 78 0 C and sublimes at -78 0 C - used by ice cream vendors; convenient because it does not leave behind any liquid

19. Changes in State Changes in State - solid changes to vapour without going through the liquid state e.g. Iodine crystals (when heated, changes to a violet vapour, when cooled, changes back to shiny black crystals) Sublimation

20. Video clip on Changes in State