Composition of Matter

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Composition of Matter

• Unit 2 Lecture 2
• Luminous beings are we, not this crude matter!
• -Yoda,
• on the nature of The Force

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Composition

• Pure Substance
• Follow exact measures or proportions
• Made up of only one kind of particle
• Mixtures
• Can be any amounts or kinds of particles

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Pure Substances

• Elements
• found on the Periodic Table
• made of only one kind of atom
• all atoms of an element are the same
• Examples?

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Pure Substance

• Compounds
• two or more atoms chemically combined
• follows a formula
• cannot be separated except
• by chemical means
• to form a new compound

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Element or Compound?

• oxygen O2
• carbon dioxide CO2
• sodium chloride NaCl
• calcium Ca
• carbon tetrachloride CCl4

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Mixtures

• Two Types
• Homogenous
• homo the same
• genous kind, or type
• Heterogenous
• hetero different

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Mixtures cont.

• Homogenous Mixture
• the same throughout
• particles so small or so well mixed that the
  particles cant be seen
• AKA solutions

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Solutions

• AKA Homogenous Mixture
• made of any phase in any other phase
• solid in liquid, gas in liquid, etc.

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Solutions cont.

• have two parts
• solute substance being dissolved, usually in
  less amount
• solvent substance doing the dissolving,
  usually in greater amount
• it is not possible to distinguish solute from
  solvent if in solution

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Solutions cont.

• Soluble
• substance can be dissolved in a given solvent
• ex sugar in water
• Insoluble
• substance cannot be dissolved in a given solvent
• ex sand in water

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Practice

• If air is 78 Nitrogen and 21 Oxygen, which is
  the solvent?
• What is the solute in orange juice?
• Which is the solvent in sweet tea?
• What is the solute in muddy water?

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Types of Solutions

• Alloy
• solutions of metals
• ex brass zinc copper, steel iron
  carbon,sterling silver silver copper
• Amalgam solution in Mercury (liquid metal)
• ex silver mercury used in dentistry
• Aqueous Solutions uses water as the solvent

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Types of Solutions cont.

• Concentrated
• high ratio of solute to solvent
• Dilute
• low ratio of solute to solve

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Making a Solution

• Surround and Separate
• Particles of the solvent pull particles of solute
  into solution

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Speeding Up Solutions

• Agitation
• Stirring makes particles collide more often
• Surface Area
• Grinding up a solute makes it easier to surround
  and separate them into solution

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Speeding Up Solutions cont.

• Temperature
• Heating a solution speeds up the particles,
  increasing the number of collisions
• NOTE When dissolving a gas in a liquid, a colder
  liquid slows down the gas particles and dissolves
  more total gas

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Agitation, Temp, or Surface Area?

• Which method of speeding up a solution explains
  why a powdered aspirin works faster than a
  tablet?
• Which method of speeding up a solution explains
  why sugar dissolves better in fresh tea than iced
  tea?
• Which method of speeding up a solution explains
  why Kool-Aid powder has to be stirred into water?
• Which method of speeding up a solution explains
  why soup mix dissolves faster than bouillon
  cubes?

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Amount of Solute

• Solubility how well a substance will dissolve
  in 100g of water at a given temperature
• differs with each substance and temperature

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Saturation of the Solute

• Unsaturated
• more solute can be dissolved in solution
• Saturated
• no more solute can be dissolved in solution
• Saturation Point point at which saturation
  happens

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Saturation of Solute cont.

• Supersaturated
• more solute than solvent can typically hold is
  dissolved due to temperature or other change
• after temp decreases, excess solute may stay in
  solution
• excess solute will come out of solution if
  disturbed until it reaches the saturation point

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Saturation of Solute contd

• Supersaturation How we make Rock Candy!

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Heterogeneous Mixtures

• Heterogenous Mixtures
• mixtures that are not well mixed
• not the same throughout
• particles are so large that they can be seen or
  picked out
• ex sand in water

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Heterog. Mixtures contd

• Two types
• Suspensions
• temporary mixtures
• particles settle out upon standing
• ex mud water w/ soil, clay, or silt, paint,
  dust in air, flour in water

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Heterogeneous Mixtures contd

• Two types
• Colloids
• particles do not settle out they are
  suspended, but not dissolved
• appears as a homogeneous mixture, but the
  particles scatter light (Tyndall Effect)
• ex milk, styrofoam, fog, mayo, smoke, blood

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Heterog. Mixtures contd

• Tyndall Effect scattering of light through the
  particles of a colloid
• ex can see flashlight beam through fog
• cant see tyndall effect in clear substance