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The Particulate Nature of Matter

Syllabus objectives : Describe the solid , liquid and gaseous states of matter and explain their interconversion in terms of the kinetic particle theory and of the energy changes involved. Describe and explain evidence for the movement of particles in liquid and gases.

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The Particulate Nature of Matter

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  1. Syllabus objectives : Describe the solid, liquid and gaseous states of matter and explain their interconversion in terms of the kinetic particle theory and of the energy changes involved. Describe and explain evidence for the movement of particles in liquid and gases. The Particulate Nature of Matter

  2. Matter - a Particle Explanation • Matter is anything that occupies space and has mass. • Matter is made up of small particles - Democritus By convention there is color, by convention sweetness, by convention bitterness, but in reality there are atoms and space. -Democritus 460-371 BC

  3. The Kinetic Particle Theory The Kinetic Particle theory of matter states that • all matter is made up of tiny particles; • all particles are in constant random motion

  4. Particulate Nature of Matter - Evidence • From Diffusion experiments… When a few drops of bromine are placed into a gas jar of air, the red-brown bromine vapour spreads slowly upwards until the whole jar is filled with a uniform brown vapour.

  5. Particulate Nature of Matter - Evidence • From Diffusion experiments… …observations can be explained if we accept the idea that the substances are made up of small particles in constant motion.

  6. Particulate Nature of Matter - Evidence • From Diffusion experiments… ..and during diffusion, the bromine particles move into the spaces between the air particles while the air particles move into the spaces between the bromine particles..

  7. Particulate Nature of Matter - Evidence • From changes in volume - mixing water & alcohol …observation can be explained if we agree that water and ethanol are made of particles. There are empty spacesbetween the ethanol particles. The water particles move into these spaces. 50 cm3 of water mixed with 50 cm3 of alcohol gives 98 cm3 of mixture

  8. Particulate Nature of Matter - Evidence • From changes in volume - mixing water & alcohol …observation can be explained if we agree that water and ethanol are made of particles. There are spaces between the ethanol particles. The water particles move into these spaces. By convention there is color, by convention sweetness, by convention bitterness, but in reality there are atoms and space. -Democritus 460-371 BC

  9. Particulate Nature of Matter - Evidence • From changes of state

  10. Particulate Nature of Matter - Evidence • Others - dissolving, fusing of metals

  11. Atoms Molecules Ions The Particles of Matter

  12. The 3 States of Matter solid liquid gas Property Definite mass    Definite shape  Definite volume 

  13. The Kinetic Particle Theory The Kinetic Particle theory of matter states that • all matter is made up of tiny particles; • all particles are in constant random motion

  14. The 3 States of Matter

  15. solid liquid gas Property The 3 States of Matter Packing of particles closely packed far apart Arrangement of particles Orderly Not orderly Not orderly vibrate and rotate about fixed positions move rapidly and at random in any direction vibrate and slide over one another Movement of particles Attractive forces between particles very strong less strong almost no

  16. The Solid State Property Explanation particles cannot move freely; can only vibrate about fixed positions • Definite shape • Definite volume • Cannot be compresssed Particles are packed very closely together

  17. The Liquid State Property Explanation • No definite shape particles can slide over one another • Cannot be compresssed; has fixed volume Particles are packed close together

  18. The Gaseous State Property Explanation • No definite shape or volume particles can move about rapidly and randomly in any direction as forces between particles are weak • Can be compresssed Particles are far apart, with a lot of empty space between them

  19. Changes of State GAS boiling condensation sublimation condensation melting SOLID LIQUID freezing

  20. Melting - in terms of Kinetic Particle Theory • When a solid is heated, heat energy is absorbed. This causes the particles to gain kinetic energy and to vibrate faster. • At a certain temperature (melting point, the vibrations become so violent that the particles are able to overcome some of the attractive forces between them and break away from each other. • The solid then becomes a liquid.Melting occurs.

  21. Freezing - in terms of Kinetic Particle Theory • When a liquid is cooled, heat energy is released. This causes the particles to lose kinetic energy and to vibrate slower. • At a certain temperature (freezing point, the vibrations become so slow that the particles are unable to overcome the attractive forces between them and are drawn towards each other in orderly and fixed positions. • The liquid then becomes a solid. Freezing occurs.

  22. Boiling - in terms of Kinetic Particle Theory • When a liquid is heated, heat energy is absorbed. This causes the particles to gain kinetic energy and move faster. • At a certain temperature boiling point), the vibrations become so violent that the particles throughout the liquid are able to break away from the forces holding them together. • The liquid then becomes a gas. Boiling occurs.

  23. Sublimation - in terms of Kinetic Particle Theory • When the solid is heated, heat energy is absorbed. Particles gain kinetic energy and move faster. • At a certain temperature the vibrations become so violent that the particles break free completely from each other, and move randomly. • The solid then becomes a gas directly. Sublimation occurs.

  24. melting completes melting starts temperature (ºC) melting point LIQUID SOLID + LIQUID SOLID temperature remains constant. Why? time from start (min) Heating Curve Heat energy absorbed by the particles is used to overcome the forces of attraction holding the particles together in their fixed positions.

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

  26. Evaporation vs Boiling Similarity : Both involve the change of state from liquid to gas. Differences :

  27. - 460C 250C 1670C s  l l  g Predicting physical states Substance X has m.p. -460C and b.p. 1670C. What is its physical state at (i) room temperature (ii) -100C (iii) -500C ? LIQUID GAS SOLID

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