THE KINETIC THE KINETIC MOLECULAR MOLECULAR

THEORYTHEORY

BASIC ASSUMPTIONSBASIC ASSUMPTIONS

1. Matter is made up of tiny, basic units of 1. Matter is made up of tiny, basic units of structure called structure called “atoms”“atoms”

2. Atoms are neither divided, created, nor 2. Atoms are neither divided, created, nor destroyed during a physical or chemical change.destroyed during a physical or chemical change.

3. An element is made up of its own kind of atom, 3. An element is made up of its own kind of atom, which is different from the atoms of which is different from the atoms of other elements.other elements.

A. MoleculesA. Molecules

4. Compounds are composed of atoms of 4. Compounds are composed of atoms of two or more elements that join together in two or more elements that join together in definite proportions.definite proportions.

MoleculeMolecule – a tightly bound group of atoms in – a tightly bound group of atoms in which the atoms maintain their identity; which the atoms maintain their identity; smallest ultimate particle of matter than can smallest ultimate particle of matter than can exist; smallest particle of a compound, or a exist; smallest particle of a compound, or a gaseous element that can exist and still retain gaseous element that can exist and still retain the characteristic properties of a substance.the characteristic properties of a substance.

Take Note:Take Note: Some atoms of gases exist in nature as Some atoms of gases exist in nature as diatomic diatomic moleculesmolecules – 2 atoms of the same element paired – 2 atoms of the same element paired together.together.

B. Molecules Interact B. Molecules Interact

1. Cohesion forces1. Cohesion forces – (n. cohesion) attractive – (n. cohesion) attractive force between molecules of the same kind.force between molecules of the same kind.

2. Adhesive force2. Adhesive force – (n. adhesion) attractive – (n. adhesion) attractive force between molecules of the same force between molecules of the same kind.kind.

C. Phases of Matter C. Phases of Matter

1. Solids1. Solids• have definite shape and volumehave definite shape and volume because of the fixed distances between because of the fixed distances between their molecules and the presence of their molecules and the presence of strong cohesive forces between them.strong cohesive forces between them.

• their molecules vibrate at fixed point and their molecules vibrate at fixed point and move around in equilibrium positionmove around in equilibrium position..• their density is determined by the their density is determined by the masses of the molecules and the masses of the molecules and the spacing between themspacing between them..

• its hardness is dependent on its resistance its hardness is dependent on its resistance to forces that tend to push their molecules to forces that tend to push their molecules apart. apart.

2. Liquids2. Liquids• its molecules are not confined to an its molecules are not confined to an equilibrium positionequilibrium position..• their molecules are close together and their molecules are close together and bound by cohesive forces that are not as bound by cohesive forces that are not as strong as that of solids. strong as that of solids. Allowing Allowing the molecules to move from place the molecules to move from place to place within the liquid.to place within the liquid.

• the molecular forces are strong enough to the molecular forces are strong enough to give the liquid a definite volume but not give the liquid a definite volume but not strong enough to give it a definite shape strong enough to give it a definite shape (it (it takes the shape of the container).takes the shape of the container).

3. Gases3. Gases• its molecules are acted upon by weak its molecules are acted upon by weak cohesive forces.cohesive forces.• its molecules are relatively far apart and its molecules are relatively far apart and move freely in a constant, random move freely in a constant, random motion motion which often changes as it which often changes as it collides with other moleculescollides with other molecules..

D. Molecules MoveD. Molecules Move

““Molecules of a gas will bounce around among the Molecules of a gas will bounce around among the molecules of the air, slowly until it becomes evenly molecules of the air, slowly until it becomes evenly

distributed.” distributed.” (process of diffusion)(process of diffusion)

Diffusion - Diffusion - mix with another substance mix with another substance by by movement of particles.movement of particles.Take Note:Take Note: Rudolf Clausius – “temperature is proportional Rudolf Clausius – “temperature is proportional to the average kinetic energy of its molecules ~ to the average kinetic energy of its molecules ~ the greater the temperature, the greater is its the greater the temperature, the greater is its molecules’ motion”molecules’ motion”

TEMPERATURETEMPERATURE

The degree or intensity of The degree or intensity of heat present in a substance or heat present in a substance or object ~ how hot or how cold object ~ how hot or how cold

is something.is something.A. ThermometersA. Thermometers

An instrument for measuring the An instrument for measuring the hotness or coldness of an object.hotness or coldness of an object.

1. Dial thermometer – bimetallic strips1. Dial thermometer – bimetallic strips2. Glass thermometer – Mercury or 2. Glass thermometer – Mercury or Colored alcoholColored alcohol

B. Thermometer ScalesB. Thermometer Scales

1.1. Fahrenheit ScaleFahrenheit Scale – (named after Ger. – (named after Ger. physicist physicist Gabriel Daniel FahrenheitGabriel Daniel Fahrenheit) ) based on the freezing and boiling point based on the freezing and boiling point of water at normal atmospheric of water at normal atmospheric pressure ~ 32pressure ~ 32ºF - freezing pt. and ºF - freezing pt. and 212ºF – boiling pt.212ºF – boiling pt.

2. Celsius Scale2. Celsius Scale – (named after Swed. – (named after Swed. astronomer astronomer Anders C. CelsiusAnders C. Celsius) based ) based on the freezing and boiling point of on the freezing and boiling point of water at normal atmospheric pressure water at normal atmospheric pressure ~ 0~ 0ºC - freezing pt. and 100ºC – ºC - freezing pt. and 100ºC – boiling pt.boiling pt.

3. Kelvin Scale3. Kelvin Scale – (named after Brit. – (named after Brit. physicist physicist William T. KelvinWilliam T. Kelvin) erased the ) erased the arbitrary assigned reference points, arbitrary assigned reference points, thus called not a thus called not a relative scalerelative scale but an but an Absolute temperature scaleAbsolute temperature scale. 0. 0 = nothing = nothing – – Absolute ZeroAbsolute Zero ~ lowest temperature ~ lowest temperature possible, occurring when all random possible, occurring when all random motion of molecules has ceased. In this motion of molecules has ceased. In this scale: 273K – freezing pt. of water; scale: 273K – freezing pt. of water; 373K – boiling pt.373K – boiling pt.

HEATHEAT

Used to describe the movement Used to describe the movement of energy between objects of of energy between objects of

different temperature are different temperature are brought together; brought together; is the is the

measure of the internal energy measure of the internal energy that has been absorbed or that has been absorbed or

transferred from one body to transferred from one body to another.another.

A. Measures of HeatA. Measures of Heat

CalorieCalorie – the amount of energy required – the amount of energy required to increase the temperature of 1 g of to increase the temperature of 1 g of water by 1water by 1°C.°C.

KilocalorieKilocalorie – the amount of energy – the amount of energy required to increase the temperature of required to increase the temperature of 1 kg of water by 11 kg of water by 1°C.°C.

British Thermal Unit (BTU) British Thermal Unit (BTU) – the – the amount of energy required to increase amount of energy required to increase the temperature of 1 lb of water by the temperature of 1 lb of water by 11°F.°F.

SPECIFIC HEATSPECIFIC HEAT

A.A. Variables that Influence the amount Variables that Influence the amount of Heatof Heat

1. Initial temperature of the liquid1. Initial temperature of the liquid2. Amount of liquid in a container2. Amount of liquid in a container3. Nature of the liquid3. Nature of the liquid

B. Significance of the variablesB. Significance of the variables

1. The amount of heat required is proportional 1. The amount of heat required is proportional to the change in temperature.to the change in temperature.2. The amount of heat required is proportional 2. The amount of heat required is proportional to the amount of liquid.to the amount of liquid.3. Different materials require different amounts 3. Different materials require different amounts of heat .of heat .

HEAT FLOWHEAT FLOW

A. ConductionA. Conduction - the transfer of energy from a region of - the transfer of energy from a region of high temperature to a region of low high temperature to a region of low temperature ~ energy is transferred from temperature ~ energy is transferred from one molecule to anotherone molecule to another..

B. ConvectionB. Convection - - transference of mass or heat within a fluid transference of mass or heat within a fluid

caused by the tendency of warmer and less caused by the tendency of warmer and less dense material to rise.dense material to rise.

C. RadiationC. Radiation - - energy emitted as electromagnetic waves or energy emitted as electromagnetic waves or

subatomic particlessubatomic particles; ; (radiant energy ~ (radiant energy ~ energy that can move through space). energy that can move through space).

HEAT, ENERGY, AND HEAT, ENERGY, AND MOLECULAR THEORYMOLECULAR THEORY

A.A. Phase ChangePhase ChangeA type of change that takes place when A type of change that takes place when solid/liquid/gas change interchangeably i.e. solid/liquid/gas change interchangeably i.e. solid to liquid, liquid to gas, gas to liquid solid to liquid, liquid to gas, gas to liquid etc. etc.

A phase change always absorbs or release the energy A phase change always absorbs or release the energy ~ a type of heat not associated with a temperature ~ a type of heat not associated with a temperature change. change.

1. Evaporation 1. Evaporation – liquid to gas– liquid to gas2. Condensation 2. Condensation – gas to liquid– gas to liquid3. Freezing 3. Freezing – Liquid to solid– Liquid to solid4. Melting 4. Melting – solid to liquid– solid to liquid5. Sublimation 5. Sublimation – solid to gas– solid to gas6. Deposition 6. Deposition – gas to solid– gas to solid

B. Latent Heat of FusionB. Latent Heat of FusionThe heat involved in a solid-liquid phase The heat involved in a solid-liquid phase change in melting or freezing. change in melting or freezing.

B. Latent Heat of VaporazationB. Latent Heat of VaporazationThe heat involved in a liquid-gas phase The heat involved in a liquid-gas phase change where there is evaporation or change where there is evaporation or condensation. condensation.

EVAPORATION AND EVAPORATION AND CONDENSATIONCONDENSATION

A. Increasing the rate of evaporation A. Increasing the rate of evaporation

1. Increasing the temperature1. Increasing the temperature

2. Increasing the surface area2. Increasing the surface area3. Removal of water vapor from the surface of 3. Removal of water vapor from the surface of

the liquidthe liquid4. Increasing pressure 4. Increasing pressure