Mixtures by dffhrtcv3

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									   Mixtures

Chapters 2 and 15
              Types of Matter
 Matter – anything that takes up space and has
  mass
  – “see” atoms with STM
  – Element – a substance that contains only 1 type of
    atom
  – Compound – a substance made of atoms combined
    by bonding in whole number ratios
 Phases of matter:
  – Solid – least energy, definite shape and volume
  – Liquid – mid energy, definite volume but not shape
  – Gas – most energy, no fixed shape or volume
  – All types of matter can become all phases if they
    get hot or cold enough
          Changes in Matter
 Physical change
  – The molecules/elements involved aren’t
    changed (no new substance is formed)
  – Often reversible
  – Ex. Phase change, mixtures
 Chemical change
  – A reaction occurs and new compounds are
    formed (new substances are created)
  – Often permanent
  – Ex. Rusting, cooking, burning, rotting
                    Mixture
 A physical combination of 2 or more
  substances
  – Can be elements or compounds
  – Nothing new is formed (physical change)
  – Can be separated back into its components by
    filtering, distillation, chromotography, or other
    physical means
  – Can be between things of the same phase or
    things in various phases
  – Ex. Salt water, atmosphere, gold jewelry
           Types of Mixtures
 Homogeneous
  – Resulting mixture is the same throughout
    (evenly mixed)
  – Also called a solution
  – Ex. Salt water
 Heterogeneous
  – Resulting mixture has different concentrations
    of the parts in different places
  – Ex. Sand and water, chocolate chip cookies
             Parts of a Solution
 Solvent – the thing that is present in the larger
  amount in a solution
   – Water is the universal solvent (many things dissolve in
     it)
 Solute – the thing that is present in the lesser
  amount in a solution
 The solute is dissolved into the solvent to make a
  solution
 Both the solute and solvent can be in any phase
 Polar solvents dissolve polar solutes, nonpolar
  solvents dissolve nonpolar solutes
        How Solutes Dissolve
 In order for a substance to dissolve in a
  solvent, a “hole” must be created for that
  molecule to fit into
  – They must have the same types of
    intermolecular interactions as the solvent
  – The solute replaces the interactions that occur
    normally between molecules of the solvent
  – Remember, ionic compounds split into 2
    separate ions when placed in water. These
    ions then interact with the polar water
    molecules, which is why they dissolve in water.
        Increasing Dissolution
 Heat the solution
  – It increases the molecular speed and so
    increases the interactions between solute and
    solvent
 Increase the surface area of the solute
  – More parts of the solute touching the solvent
    increases the interactions
 Stir the solution
  – Like temperature, movement increases the
    interactions
   Adding Solutes Changes the
 Physical Properties of a Substance
 Colligative property – the amount of a substance
  matters more than the type of substance involved
  – More particles gives a greater effect
 Adding solute increases the boiling point of a
  substance
  – Interactions with solute keep water from being able to
    escape in air bubbles
 Adding solute decreases the freezing point of a
  substance
  – Interactions with solute keep water from being able to
    create the intermolecular forces required to create a
    solid
    Concentrations of Solutions
 Concentrated – a lot of solute is dissolved
 Diluted – a little solute is dissolved
 Unsaturated – more solute could still be
  dissolved
 Saturated – any more solute would be
  unable to dissolve
 Supersaturated – the solution has been
  “tricked” into dissolving more solute than
  normally possible
                Mass Percent
 Way to measure the concentration of a solution
 Mass % = mass solute          x 100
                mass solution
 Ex. What is the mass percent of a salt water
  solution if 1.0 g of NaCl is dissolved into 49.0 g of
  water?
                   1 g x 100 = 2.0%
                   50g
                    Molarity
 Another way to measure concentration
  – Better than mass % because the mass of the
    compounds don’t matter
 M = mol solute
       liters solution
 Ex. What is the molarity of a 1.50 L solution
  containing 11.5 g NaCl?
11.5 g NaCl        1 mol NaCl      =     0.288 mol
                   40 g NaCl
M = 0.288 mol =         0.192 M NaCl
      1.50 L
            Diluting Solutions
 Solutions are often stored in the lab at high
  concentrations to conserve space, then diluted by
  adding more solvent to create a usable
  concentration
 M1V1 = M2V2
 Ex. What volume of 16 M HCl must be used to
  prepare 1.5L of a 0.1 M HCl solution?
           16 (V) = 0.10 (1.5)
              16        16
V = 0.0094 L

								
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