The Nature of MatterMr. Gilbertson

Chemistry

Chapter 3Chapter 3

Solids, Liquids, and GasesSolids, Liquids, and Gases

Matter

Has Has MassMass Takes up Space (Takes up Space (VolumeVolume)) Exhibits the property of Exhibits the property of InertiaInertia States of matterStates of matter

SolidSolid – definite volume, definite shape – definite volume, definite shape LiquidLiquid – definite volume, no definite shape – definite volume, no definite shape GasGas – no definite volume, no definite shape – no definite volume, no definite shape PlasmaPlasma – like gas, exists only at very high – like gas, exists only at very high

temperatures or of very high energy temperatures or of very high energy particlesparticles

State of Matter

Depends on the temperature (ultimately the average Depends on the temperature (ultimately the average internal Kinetic energy of motion of the particles.internal Kinetic energy of motion of the particles.

Crystalline substances undergo phase changes at Crystalline substances undergo phase changes at specific temperatures (water, steel, lead, etc.).specific temperatures (water, steel, lead, etc.). Melting/Freezing Point – transition temperature Melting/Freezing Point – transition temperature

between solid and liquid.between solid and liquid. Boiling Point – temperature at which a liquid Boiling Point – temperature at which a liquid

changes rapidly to a gas.changes rapidly to a gas. Amorphous substances have no definite transition Amorphous substances have no definite transition

temperatures (wax, butter, glass, etc.).temperatures (wax, butter, glass, etc.).

States of Matter

Solids

Has a Has a definite volumedefinite volume - can’t be compressed. - can’t be compressed. Has a Has a definite shapedefinite shape - can’t be changed without - can’t be changed without

the application of force.the application of force. Classification:Classification:

CrystallineCrystalline – particles are arranged in a – particles are arranged in a repeating geometric pattern (crystal).repeating geometric pattern (crystal).

AmorphousAmorphous (Noncrystalline) – particles are (Noncrystalline) – particles are said to “have no form”, many may be thought said to “have no form”, many may be thought of as thick liquids.of as thick liquids.

Particles are close together and unable to move Particles are close together and unable to move past one another, though they do vibrate in place.past one another, though they do vibrate in place.

Solids - Crystalline

Arrangement of particles in a solid – the crystalline lattice

Liquids No definite shapeNo definite shape – takes the shape of its container. – takes the shape of its container. Has a Has a definite volumedefinite volume – like solids can’t be compressed. – like solids can’t be compressed. Particles in a liquid.Particles in a liquid.

have have greater energygreater energy and therefore faster motion and therefore faster motion than those of solids.than those of solids.

are are spaced further apartspaced further apart than in solids, thus than in solids, thus allowing particles to move past one another, this allowing particles to move past one another, this explains why liquids can flow.explains why liquids can flow.

are are attracted to each otherattracted to each other and so they do stick and so they do stick together.together.

Gases No definite shape – like liquids they take No definite shape – like liquids they take

the shape of their container (“springy”).the shape of their container (“springy”). No definite volume – with the application No definite volume – with the application

of a force they can be compressed.of a force they can be compressed. Particles of a gas:Particles of a gas:

Have a large amount of energy and are Have a large amount of energy and are able to separate completely.able to separate completely.

Have relatively low attraction for each Have relatively low attraction for each other so they can expand and be other so they can expand and be compressed easily.compressed easily.

Plasma

Like a gas, Like a gas, No definite volume, No No definite volume, No definite shapedefinite shape..

Exists only at very Exists only at very high temperatureshigh temperatures or or of very of very high energyhigh energy particles. particles.

Particles are Particles are chargedcharged both positive and both positive and negative (protons and electrons) Atoms negative (protons and electrons) Atoms can’t maintain integrity.can’t maintain integrity.

Form in which matter of sun and stars Form in which matter of sun and stars exists, also found in fluorescent lights.exists, also found in fluorescent lights.

Plasmas

Kinetic Theory of Matter

All matter is composed of particles All matter is composed of particles (atoms or molecules).(atoms or molecules).

All particles are in motion (vibration).All particles are in motion (vibration). Motion is directly proportional to the Motion is directly proportional to the

temperature. As temperature increases temperature. As temperature increases so does the motion of the particles.so does the motion of the particles.

At absolute zero there is no motion (0.0 K At absolute zero there is no motion (0.0 K or –273or –273ooC).C).

Particle SpacingAs the phase changes, the average distance between the particles increases. In solids the particles vibrate within a crystalline lattice. In liquids the particles move to a distance equal to one diameter of the particle or more, attractive forces are still strong. In gases the particles move far enough apart to overcome all attraction between particles.

Molecular Forces

Thermal Expansion

The general increase in volume as a result of an The general increase in volume as a result of an increase in temperature. Change in volume is said to increase in temperature. Change in volume is said to be directly proportional to the change in be directly proportional to the change in temperature.temperature.

Matter also tends to contract as a result of Matter also tends to contract as a result of temperature changes.temperature changes.

Explained by Kinetic Theory of Matter.Explained by Kinetic Theory of Matter. When heated the particles move faster so they When heated the particles move faster so they

push harder against one another and so they push harder against one another and so they move apart in all directions.move apart in all directions.

A thermometer demonstrates this property.A thermometer demonstrates this property.

Thermal Expansion

An expansion joint is ofteninserted into roads and bridges to prevent damage when the temperatures change. Space must be left between the railroad track sections for the same reason.

Thermal ExpansionThe fact that materials expand and contract predictably when heated or cooled allows us to make thermostats using bimetallic strips. Bimetallic strips use two metals bonded to each other, since each has a different coefficient of expansion one side expands more than the other when heated. This causes the strip to bend, this fact can be used to open or close a circuit to activate a heating or cooling system.

Changes in State

Evaporation – change from a liquid to a Evaporation – change from a liquid to a vapor at temperatures below boiling vapor at temperatures below boiling point, often used to cause cooling.point, often used to cause cooling.

Sublimation – change from a solid to a Sublimation – change from a solid to a gas without passing through the liquid gas without passing through the liquid state.state.

Condensation – the change from a gas to Condensation – the change from a gas to a liquid at temperatures below the a liquid at temperatures below the boiling point.boiling point.

Evaporation

Particles of a liquid will continue to evaporate until the pressure exerted by the particles leaving is equal to the pressure of the atmosphere, at which time the particles will condense at the same rate as they evaporate. This is known as equilibrium.

Condensation

Occurs when water vapor is cooled below its boiling point, as altitude increases boiling point decreases.

Distillation - using phase changes

Phase Changes

The phase of matter is dictated by the temperature and the pressure conditions. The graph above shows the temperature and pressure conditions necessary to cause a phase change. The lines represent transitions, above the critical point it is impossible to distinguish between a liquid and a gas. The triple point is the temperature and pressure conditions necessary to exist in all three states simultaneously. Triple point Demo

Heat and State Changes Heat of fusionHeat of fusion – The amount of heat energy – The amount of heat energy

which is necessary to change a solid to a which is necessary to change a solid to a liquid or vice versa. (for water 334 kJ/kg).liquid or vice versa. (for water 334 kJ/kg). Heat must be absorbed to melt, must be lost Heat must be absorbed to melt, must be lost

to freeze.to freeze. Heat of vaporizationHeat of vaporization – The amount of heat – The amount of heat

energy which is necessary to change a liquid energy which is necessary to change a liquid to a gas or vice versa. (for water 2260 kJ/kg).to a gas or vice versa. (for water 2260 kJ/kg). Heat must be absorbed to vaporize, heat Heat must be absorbed to vaporize, heat

must be lost to condense.must be lost to condense.

As a sample of ice is warmed and the temperature is measured every 30 seconds, the particles of solid water absorb the applied heat energy.

As heat energy continues to be supplied, you may notice that the solid water now begins to appear as a liquid, but the temperature is not rising. To change a solid to a liquid, many forces must be overcome, the energy is known as the heat of fusion.

Once the work of melting is accomplished, the applied heat energy causes the water particles making up the liquid to move faster. As you can see from the graph, the temperature begins to rise.

Once the boiling has been reached, the liquid becomes a gas, and the temperature again remains constant, At the heat of vaporization, the forces of attraction between particles are totally overcome. This requires 2260kJ of energy.

Video about chemical and physical changes

Physical and Chemical Changes

THE END