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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