Kinetic Model of Matter Textbook Chp 9 Pg

Kinetic Model of Matter Textbook Chp 9 Pg 153 -166

For this topic… • 80% is already covered in Chemistry. This is a quick revision • This is a purely qualitative topic. There are no calculations

Topics • • • Solids, Liquids & Gases Brownian Motion Kinetic Model of Solids Kinetic Model of Liquids Kinetic Model of Gases Gas Laws

Properties of Solids, Liquids, Gases Solids Fixed Shape Fixed Volume Liquids Gases No fixed shape Fixed Volume No fixed volume Incompressible Compressible High density Low Density Expands a Expands more Expands the little when heated most when heated

Brownian Motion • Robert Brown conducted an experiment by observing smoke particles under a microscope • Video: http: //www. youtube. com/watch? v=c. Dcprg Wi. QEY • Smoke particles appeared to move in a random manner • “Brownian Motion” refers to the observed movement of particles in a fluid (liquid or

Brownian Motion • Brown explained his observations that the smoke particles are being randomly bombarded by air molecules • Common mistake: what is seen is NOT air molecules (which are too small to be seen) but smoke particles • Brownian motion provides evidence that air consists of tiny particles (molecules) moving in a random manner

Kinetic Model of Matter • The Kinetic Model of Matter states that matter is made up of tiny particles (i. e. atoms and molecules) • These particles are always in continuous random motion

Kinetic Model of Solids • Particles are closely packed together (lattice structure) • Large number of particles per unit volume (high density) • Particles vibrate about fixed positions • Particles held together by strong attractive forces between particles (strong inter-molecular bonds) • When solid is heated up, particles vibrate more vigorously • When enough energy is supplied, particles vibrate so strongly that strong attractive forces between particles are broken (melting to be

Kinetic Model of Liquids • Particles are randomly arranged • Particles are slightly further apart compared to solids (high density but less than solids) • Particles move around freely and randomly • While particles are not held at fixed positions, there are still strong attractive forces between particles (high inter-molecular forces) • When heated, particles move faster • When enough energy is supplied, particles move so quickly they break free from attractive forces and becomes isolated particles (boiling to become gas)

Kinetic Model of Gases • Particles are randomly arranged • Particles are far apart from each other (negligible attractive forces between them) • Particles move randomly at fast speeds • Upon heating, particles move faster

Kinetic Model of Gases • When a gas is held in a container, the collisions between the particles and the container give rise to gas pressure • 2 factors to gas pressure: • The greater the rate of collisions, the greater the pressure • The faster each molecule moves, the more forceful the collision against the container, the greater the pressure

3 Ways to Increase Pressure of Gas • Reduce the volume of the container (i. e. compress the gas) • Increases the rate of collisions between gas particles and container • Pump more gas into the container • Increases the rate of collisions between gas particles and container • Heat the gas • Increase speed of gas molecules, collisions are more forceful

Summary of Kinetic Model Distance between Particles Solid Liquid Gas Attractive Force between Particles

Gas Laws • When dealing with gases there are three main properties: • Pressure of Gas (P) • Volume of Gas (V) • Temperature of Gas (T) • There are three gas laws, each one keeping one of the three properties constant • Note: the gas laws only apply if the mass of gas is constant (i. e. no new gas is added

Fixed Pressure • If a gas has fixed pressure, • Volume is directly proportional to Temperature • VαT • e. g. when I heat a balloon of air, it will expand

Fixed Volume • If a gas has fixed volume, • Pressure is directly proportional to Temperature • PαT • e. g. when a fixed container of air is heated up, the pressure inside the container increases

Fixed Temperature • If a gas has fixed temperature, • Pressure is inversely proportional to Volume • p α 1/v • e. g. when I compress a volume of air (decrease in volume) the pressure increases

Summary of Gas Laws • When P is fixed, V α T • When V is fixed, P α T • When T is fixed, P α 1/V

Summary • Properties of Solids, Liquids, Gases • Brownian motion as evidence of Kinetic Model • Kinetic Model of Solids • Kinetic Model of Liquids • Kinetic Model of Gases (including pressure) • 3 Gas Laws

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