Science 4001 Earth and Space Science 11

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Science 4001 Earth and Space Science 11
MATTER AND MATERIALS
UNIT I Properties of materials and the kinetic
theory
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• Properties of materials and the kinetic theory
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• MATERIALS are considered substance objects from
  which things are made e.g. metals, ceramics,
  plastics, rubber, wood, glass, cement, leather,
  bone, textiles, glues, paints, dyes, solvents,
  foodstuff, medicine etc.
• Can you add a few more?

Glass is a material which can be made into these
objects
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• Properties of materials and the kinetic theory
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Material

• Common properties are
• Colour, Texture, Hardness, Flexibility,
  Strength, Density, Specific Heat Capacity,
  Conductivity (or The Converse Electrical
  Resistance), boiling point, melting point.

Object tubing
Object coin

• Objects are made up of materials which have
• Shape
• Mass
• Volume,

Object Jewellery / ornament
Object wire
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• Properties of materials and the kinetic theory
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• Properties that describe the look or feel of a
  substance, such as colour, hardness, density,
  texture, and phase, are called physical
  properties.
• Every substance has its own set of characteristic
  physical properties that we can use to identify
  that substance.
• For example, gold is an opaque, yellowish
  substance that is a solid at room temperature and
  has a density of 19300 kgm-3.

• Diamond is a transparent substance that is a
  solid at room temperature and has a density of
  3500 kgm-3.
• Water is a transparent substance that is a
  liquid at room temperature and has a density of
  1.0 kgm-3.

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• Properties of materials and the kinetic theory
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• MATTER occupies space.
• Matter generally exists as SOLIDS LIQUIDS OR
  GASES.
• Temperature and Pressure determine the state of
  matter.
• Energy is gained/lost when matter changes its
  state.

• KINETIC (PARTICLE) THEORY OF MATTER
• MATTER is made up of particles called atoms or
  molecules
• Particles are in constant random motion
  (rotation, vibration and / or translate).
• Particles collide with each other if they move
  about.
• They collide with the particles in the walls of
  the container if they move about.
• Energy is exchanged between particles during
  collision.

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• Properties of materials and the kinetic theory
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• THE THREE STATES OF MATTER
• The Kinetic theory of matter states that all
  matter is made up of particles, and exists in one
  of three states, either solid, liquid or gas.
• Their arrangements are often summarised as
  follows

Solid
Liquid
Gas
In the solid state particles are in a fixed
arrangement but can vibrate in 3 dimensions and
rotate but cannot move about. In the liquid state
particles are free to move about and can vibrate
in 3 dimensions and rotate. In the gaseous state
particles are free to move about and can vibrate
in 3 dimensions and rotate.
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• Properties of materials and the kinetic theory
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Heat causes the bonds between the particles to
weaken so when heated the temperature rises then
solids melt to liquids, whose temperature will
rise until they vaporize to gases.
The reverse happens when substances loose heat
(cool). Loss of heat causes the bonds between the
particles to strengthen so when cooled the
temperature drops then gases condense to liquids,
whose temperature will drop until they freeze to
solids.
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• Properties of materials and the kinetic theory
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• KINETIC THEORY OF GASES
• Gas molecules move about with high speeds.
• Gas molecules are far apart.
• The forces between molecules are much less
  (negligible) than solids or liquids.
• Increased temperature causes more vigorous
  motion in the molecules.
• Gases expand to fill their container.
• When molecules collide with the walls of the
  container this is called pressure.

• There are two variables affecting the volume of a
  gas
• Increased pressure decreases volume.
• Increased temperature increases volume.

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• Properties of materials and the kinetic theory
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• EVIDENCE FOR KINETIC THEORY OF GASES
• Brownian motion.
• Evaporation.
• melting
• Freezing
• Boiling
• Diffusion
• Condensation
• Adhesion
• Cohesion
• Surface Tension
• Osmosis.

Brownian motion
Diffusion
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• Properties of materials and the kinetic theory
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GENERAL PROPERTIES SOLIDS, LIQUIDS AND GASES
Properties Solids Liquids Gases
Arrangement of particles Closely packed, orderly fashion Randomly distributed clusters Particles further apart
Inter particle strength Very strong Moderate Very weak
Motion of particles Restricted motion Vibration, rotation. Random motion and freer to move around, vibration, rotation. Confined to the bulk of the liquid Move in clusters Random motion and freer to move around, vibration, rotation. Confined only by container walls.
Volume Constant volume Definite volume Fill any space
Compressibility Not easily compressed Pressure has small effect Easily compressed
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• Properties of materials and the kinetic theory
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EFFECT OF HEAT ON SOLIDS LIQUIDS AND GASES
States of matter Effects of Heat Rate of diffusion
Solids Expand slightly. eventually melts with small increase in volume. Temperature remains constant until all the solid melts. Very slow
Liquids Expand slightly as temperature rises. Boil eventually with large increase in volume. Temperature remains steady during boiling until all the liquid turns to gas. Slow
Gases Expand considerably at constant pressure. Pressure may increase if confined in a closed container. Rapidly
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• Properties of materials and the kinetic theory
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CHANGES IN STATE KINDS OF STATE CHANGES

• EVAPORATION AND BOILING
• In evaporation a liquid changes to a gas at a
  temperature below its boiling point.
• When a liquid is heated its particles move
  faster but at different speeds continually
  colliding with each other and with the walls of
  the container.
• Occasionally a particle acquire sufficient
  energy to escape into the vapour.
• Once boiling has started the temperature remains
  steady.

In boiling vigorous molecules form bubbles inside
the water

• The heat energy goes to separate the particles
  from one another by weakening bonds.
• The escaping particles take with them a lot of
  energy evaporation results in cooling.
• Evaporation depends on - nature of liquid,
  temperature and surface area.

EVAPORATION High energy molecules escape Moderate
energy molecules are pulled back into the
liquid Low energy molecules remain in the bulk
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• Properties of materials and the kinetic theory
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CHANGES IN STATE KINDS OF STATE CHANGES

• SUBLIMATION - In sublimation a solid changes
  directly to a gas without going through the
  liquid state.
• CONDENSATION takes place when a gas changes to a
  liquid. A gas will condense when cooled to or
  below its boiling point.
• BOILING takes place when a liquid is heated to
  its boiling point.
• FREEZING takes place when a liquid is cooled
  below its freezing point
• MELTING takes place when a solid is heated above
  its melting point.

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• Properties of materials and the kinetic theory
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HEAT AND STATE CHANGES

• LATENT HEAT OF FUSIONIf ice cubes below 0oC are
  heated, they warm up to 0oC.
• Then they begin to melt.
• Temperature stays at 0oC until all the ice melts
• The particles of the solid water (ice) absorb
  the heat energy which enables them to overcome
  the forces which hold them in place in the solid
  state and can now move about freely inside the
  bulk of the liquid.
• LATENT HEAT OF VAPORIZATION
• If water below 100oC are heated, it warms up to
  100oC.
• It begins to boil.
• Temperature stays at 100oC until all the water
  boils
• The particles of the liquid water absorb the
  heat energy which enables them to overcome the
  forces which hold them in place in the liquid
  state and can now move about freely unless
  confined in a container.
• All substances have latent heat of fusion and
  vaporization.
• These are absorbed at the melting point and
  boiling point of the substance.
• These are released at the freezing point and
  condensing point of the substance.

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• Properties of materials and the kinetic theory
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HEAT AND STATE CHANGES
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• Water
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WATER COMMON PROPERTIES

• Colorless odorless and tasteless
• Remarkable solvent properties so it contaminate
  easily
• Melting point or freezing point is 0oC
• Boiling point or condensing point is 100oC
• Density 1000kgm3
• Water is unique as it expands when it freezes
  and so has a maximum density at 40C
• PURIFICATION OF WATER
• Collection - in dams and reservoir.
• Sedimentation aluminium sulphate is added to
  help particles settle out.
• Filtration to remove suspended matter
• Chlorination to kill harmful bacteria.
• Reverse osmosis is used to remove dissolved
  salts.
• In some countries where oil is cheep distillation
  may be used to remove dissolved salts

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• Solutions
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• SOLUTION Homogeneous mixture of two or more
  substances.
• SOLUTE The substance that is dissolved
  (usually the one that is the smaller amount).
• SOLVENT The substance that does the dissolving
  (usually the one that is greater amount).
• DISSOLVE Breaking down of solute particles in
  solvent until no longer visible to the naked eyes.

• Solutions can be
• Solid in solid (e.g. Gold with copper for
  jewellery). Metals dissolved in other metals are
  called alloys. Solid metal alloys e.g. brass,
  bronze, steel or solder.
• Solid in liquid. e.g. Salt in water, nail polish
  pigments in acetone.
• Gas in solid. e.g. Hydrogen in palladium.
• Liquid in liquid e.g. Alcoholic drinks.
• Gas in liquid e.g. Oxygen in water, Carbonated
  drinks.
• Gas in gas e.g. Air

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• Solutions
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• PROPERTIES OF SOLUTIONS
• Solute and solvent are thoroughly mixed.
• Solute and solvent do not separate normally.
• Solute particles are not visible.
• Solution may be colored but transparent.
• Solute may be separated by physical means.

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• Solutions
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• DISSOLVING OF SOLUTE DEPENDS ON
• PRESSURE Significant for gases dissolved in
  liquids
• TEMPERATURE Most solids dissolve faster at
  higher temperatures but gases tend to be
  opposite.
• NATURE OF SOLUTE AND SOLVENT Like dissolves
  like.
• PARTICLE SIZE Smaller particles dissolve
  faster.
• STIRRING Helps in dissolving.
• SATURATED AND SUPERSATURATED SOLUTIONS
• SATURATED SOLUTION Contains as much solute as
  can possibly be dissolved at a given temperature
  and pressure
• SUPERSATURATED SOLUTION Contains more solute
  than can normally be dissolved in a given amount
  of solvent at a given temperature and pressure.

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• Suspensions and Colloids
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• SUSPENSIONS AND COLLOIDS
• Distinguished by their particle size
• Suspensions formed when solute particles do
  not dissolve or partially dissolve. e.g. clay in
  water, some medicines, germicidals.
• These settle out after the suspension is left
  standing for some time.

Light passing through a colloid
COLLOIDS AND EMULSIONS solute particle size
break up so that they are mid way between
solution and suspension e.g smoke, milk,
aerosols,
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• Suspensions and Colloids
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• SEPARATION OF MIXTURES
• Hand picking particles must be large enough
  and have some property that are different
  allowing them to be removed by inspection e.g.
  Picking rice.
• Decanting when one liquid floats on another e.g.
  Oil floating on water.
• Magnet sand/sulphur and iron filings.
• Flotation ping pong balls/golf balls using
  water.
• Sieves these can be some kind of mesh which
  has holes where one component is made up of
  smaller particles which can pass through the
  sieve
• Sieves can be used for separating gravel of
  different sizes
• Cloth or paper filters can be used for
  separating coffee grounds from coffee.
• Filter paper can be used in the lab to separate
  undissolved materials from a liquid.
• Evaporation to dryness a liquid solvent can be
  removed from a solution by boiling it away
  leaving the solid solute behind e.g. Sugar is
  made from cane juice.

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• Suspensions and Colloids
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• SEPARATION OF MIXTURES
• Simple or fractional distillation can be used
  to separate a liquid solvent can be removed from
  a solution by boiling it away and condensing it.
  E.g. Simple distillation for getting water from
  sea water. Fractional distillation for alcohol is
  distilled from fermented products or separation
  of crude oil into various oils and fuels.
• Dissolve one of the components of the mixture
  and evaporate to dryness e.g. Sand and salt ?
  dissolve salt in water and evaporate to dryness.
• Chromatography pigments from flour petals.
• Centrifugation Spinning the suspensions,
  colloids very quickly.

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• Suspensions and Colloids
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• HARD AND SOFT WATER
• Most sources of water, even water we drink,
  contains varying amounts and types of impurities.
  
• Certain impurities make it difficult for soap to
  lather. This type of water is called HARD WATER.
• ACTION OF SOAP ON HARD WATER
• Soap is made of Sodium(Na) stearic acid
• Calcium in hard water stearic acid from soap
  Calcium stearate (insoluble white curdy
  precipitate).
• HOW WATER BECOMES HARD
• Rain water falling through the atmosphere mixes
  with and dissolves certain acidic gases found in
  the atmosphere making the rain water acidic.
  e.g. water carbon dioxide ? carbonic acid. In
  industrial areas nitric acid and sulphuric acid
  are also formed.
• Acidic rain water falling on calcium or
  magnesium bearing rocks react with these
  substances and the products dissolve in the water
  making what is known as HARD WATER.

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• Suspensions and Colloids
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• TYPES OF HARDNESS
• Calcium carbonate CaCO3 and magnesium
  carbonate MgCO3 are insoluble rocks but acid
  rain (carbon dioxide) changes these to calcium
  calcium hydrogen carbonate Ca(HCO3)2 and
  magnesium hydrogen carbonateMg(HCO3)2 .
• Temporary hard water is caused by dissolved
  calcium and magnesium hydrogen carbonate.
• Permanently hard water is caused by dissolved
  calcium sulphate CaSO4 and also magnesium
  sulphate MgSO4 in water.
• These substances react with soap so that it does
  not lather.
• SOFTENING HARD WATER - temporary hard water
• Boiling
• Ca(HCO3)2 ? CaCO3 CO2
• Adding calcium hydroxide
• Permanently hard water
• Adding washing soda crystals sodium carbonate
• Temporary and Permanent Hardness
• Commercial water softener
• Ion exchange resin
• Distillation

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• Determining mass and volume
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• Mass is measured with a balance.
• Equal arm balances

• Spring balance

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• Determining mass and volume
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Liquid volume is measured with a measuring
cylinder.

• Read a measuring cylinder at eye level and the
  bottom of the meniscus.

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End of UNIT 1 MATTER AND MATERIALS