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.

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

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

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.

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.

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..

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 spaces between 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

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

Particulate Nature of Matter - Evidence From changes of state

Particulate Nature of Matter - Evidence Others - dissolving, fusing of metals

The Particles of Matter Atoms Molecules Ions

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

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

The 3 States of Matter

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

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

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

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

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

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.

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.

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.

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.

temperature remains constant. Why? Heating Curve temperature (ºC) melting starts temperature remains constant. Why? melting completes time from start (min) melting point 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.

Cooling Curve LIQUID SOLID LIQUID + SOLID Heat loss due to cooling is exactly balanced by the heat energy liberated as the particles attract one another to form a solid. 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)

Evaporation vs Boiling Similarity : Both involve the change of state from liquid to gas. Differences : Boiling Evaporation Takes place at boiling point of the liquid Takes place at any temperature below takes place throughout the liquid takes place at the surface of the liquid very fast process very slow process

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 - 460C s  l 250C 1670C l  g