1. 1 The Particulate Nature of Matter Chapter 1

2. 2 contents You will learn about: Properties of matter in the solid, liquid and gaseous states The Kinetic Particle Theory The inter-conversion of the states of matter

3. 3 states of matter water exist as three states of matter gas liquidsolid All substances are made of matter. The three states of matter are solid, liquid and gas

4. 4 Properties of matter in solid, liquid and gaseous states Properties of matter in solid, liquid and gaseous statesSolidsLiquidsGases ShapeFixed No fixed shape; take the shape of container No fixed shape; expand to take the shape of container Hardness Hard and is usually made of crystals Not hard and can flow easily Not hard. Can flow along a pipeline and diffuse easily DensityHigh densitymedium densityLow density CompressionNo Easily compressed VolumeFixed No fixed volume; expand to fill the container Main Features of Solids, Liquids and Gases

5. 5 The Kinetic Particle Theory The Kinetic Particle Theory states that all matter is made up of tiny particles, and these particles of matter are always in constant random motion. Scientists have gathered evidence from diffusion experiments, changes in volume and changes in states and hypothesized that matter is made up of small particles. The ancient Greeks were the first to suggest that everything is made up from particles. Thus, scientists came up with the Kinetic Particle Theory.

6. 6 particles of matter PropertySolidLiquidGas Diagrammatic representation of particles in each state Arrangement and Packing between particles Particles are in orderly arrangement and are packed very closely together. Particles are not in orderly arrangement and is closely packed together. Particles are not in orderly arrangement and are very far apart from one another. Motion of particles Particles vibrate about a fixed position Particles are free to move around the liquid and slide over each other. Particles are very far apart from each other. Forces of attraction between particles Very strong forces of attraction between particles Strong forces of attraction between particles Very weak forces of attraction between particles

7. 7 particles of matter

8. 8 Inter-conversion of states of matter melting HEAT temperature stearic acid water at 100ºC experiment to find the melting point of stearic acid When a solid is heated, particles gain kinetic energy and vibrate faster. At a certain temperature, particles would have gained enough energy to overcome the attractive forces holding the particles of solid together in fixed positions. Melting occurs. Particles now are able to move around the liquid and slide over one another. Why is a water bath used? Prevent direct heating of combustible substances

9. 9 Inter-conversion of states of matter

10. 10 changes of state melting temperature (ºC) melting starts temperature remains constant. Why? melting completes time from start (min) melting point (69°C) SOLID SOLID + LIQUID LIQUID Heat energy absorbed by the particles is used to overcome the forces of attraction holding the particles together in their fixed positions. Graph of temperature vs time plotted to depict melting process

11. 11 changes of state freezing When a liquid is cooled, particles lose kinetic energy and move slower and come closer together. At a certain temperature, particles no longer have enough energy to move around the liquid. Freezing occurs. Liquid changes into a solid and particles can only vibrate in their fixed and orderly positions. Heat energy is given out during freezing. Freezing and melting points are the same for a pure substance.

12. 12 temperature remains constant. Why? freezing completes freezing starts freezing point (=melting point) for pure substances SOLID LIQUID + SOLID LIQUID temperature (ºC) time from start (min) changes of state freezing Heat loss due to cooling is exactly balanced by the heat energy liberated as the particles attract one another to form a solid. Graph plotted to depict freezing

13. 13 changes of state boiling experiment to find the boiling point of 1,1,1-trichloroethane liquid trichloroethane thermometer condenser water out water in boiling stones HEAT liquid trichloroethane When a liquid is heated, the particles gain kinetic energy and move faster. At a certain temperature, particles throughout the liquid gain enough energy to overcome the forces of attraction holding them together in the liquid. Boiling occurs. Liquid changes into a gas. Particles are now able to move freely and randomly around at great speeds.

14. 14 changes of state boiling temperature (ºC) time from start (min) liquid is boiling between points A and B AB boiling starts at point A 0 74ºC The temperature remains constant during boiling because the heat energy is absorbed by the particles of liquid to overcome the forces of attraction holding them together. Graph plotted to depict boiling A pure substance has a fixed boiling point at a fixed pressure. Boiling point increases when pressure increases (i.e. pressure cooker) and boiling point decreases when pressure decreases. (on mountain top) Boiling occurs when the vapour pressure of the substance equals to the ambient pressure.

15. 15 changes of state evaporation BoilingEvaporation occurs only at boiling point occurs at temperatures below boiling point takes place throughout the liquid takes place at the surface of the liquid very fast processvery slow process occurs when liquids turn into gases without boiling. Evaporation occurs because some particles near the surface of the liquid have enough energy to escape as a gas. Liquids which vaporize quickly at low temperatures are called volatile liquids. Differences between Boiling and Evaporation:

16. 16 changes of state condensation sublimation When a gas is cooled, particles lose kinetic energy and move more slowly. The particles come closer to one another. At a certain temperature, the particles no longer have enough energy to move about randomly at great speed. Condensation takes place. The gas is changed into a liquid. Heat energy is given out during condensation. Change of state from solid to gas without melting. Sublimation occurs because some particles have enough energy to break off from the solid and escape as a gas. Examples include iodine, ammonium chloride and solid carbon dioxide (dry ice)

17. 17 changes of state sublimation

18. 18 melting particles energy has most are close together in disorderly arrangement in liquid shape of container has boiling are far apart and move at random in gas diffusion particles can mix together by particles can move so liquids flow because compress can be no shape has fixed shape has energy has least are close together in orderly arrangement in solid particles can only vibrate because freezing condensation sublimation