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Mixtures and
solutionsMR. BANKS
7TH GRADE SCIENCE
Mixtures
A mixture is a physical
blend of two or more
substances.
These substances can be
atoms and/or compounds.
Unlike a compound, the
atoms in mixtures are not
bonded together.
Mixtures
Mixtures can exist as
solids, liquids, or gasses.
Mixtures
Mixtures are made by
combining together two
or more substances that
don’t react.
Each part of a mixture
keeps its own properties.
The substances in a
mixture don’t react with
one another.
Mixtures
There are two types of
mixtures.
Homogeneous
Heterogeneous
Mixtures
Heterogeneous mixtures
are mixtures where the
substances that make
them are not evenly
distributed.
Usually there are mixtures
of two solids.
Mixtures
Homogeneous mixtures
are mixtures where the
materials are evenly
distributed throughout.
English lesson!
The prefix “homo” means
“same”
If you take a sample from
any part of the mixture it
will be exactly the same
as any other part.
The prefix “hetero” means
“different”
If you take a sample from
a part of the mixture it will
look different from
another part.
Heterogeneous vs Homogeneous
What is it?
Cheerios
Homogeneous
What is it?
Trail Mix
Heterogeneous
What is it?
Kool - Aid
Homogeneous
What is it?
Water
Homogeneous
What is it?
White Vinegar
Homogeneous
What is it?
Italian Salad Dressing
Heterogeneous
Raisin Bran
Orange juice
Air
Chunky Soup
Hamburger
Cake Batter
Paint
Salad
Rock
Answers:
Raisin Bran – heterogeneous
Orange Juice – homogeneous
Air – heterogeneous
Chunky Soup – heterogeneous
Hamburger – heterogeneous
Cake Batter – homogeneous
Paint – homogeneous
Salad – heterogeneous
Mineral Rock - heterogeneous
Solutions
Solutions are mixtures that
consist of microscopic
particles.
Solutions are formed when
one substance dissolves in
another.
Solutions are almost always
homogeneous mixtures.
Solutions are always liquids
after the substance has
dissolved.
Solutions
A solution always has a substance that is
dissolved and a substance that does the
dissolving.
The substance that is dissolved is the solute.
The substance that does the dissolving is the
solvent.
Kool-aid Mix(solute)
Water(solvent)
Kool-aid(solution)
Separating mixtures
When two or more
substances are mixed.
They are combined, but
do not chemically
change or bond.
They retain their normal
properties.
This means that all
mixtures CAN be
separated.
Separating mixtures
Hand separation – basically using your hands to
separate things.
Only possible when the things mixed are large,
can be picked up, and can be distinguished by
sight.
Separating mixtures
Magnetic attraction – if one of the substances in
the mixture is made of a magnetic metal you can
use a magnet to separate that part out.
Useful for separating things made of iron from
other materials.
Separating mixtures
Filtration – useful for
separating solids from
liquids, or larger solids
from smaller solids.
Involves passing the
mixture through a porous
material (a material with
holes).
Fluid and smaller solids will
pass through, but not the
larger solids.
Separating mixtures
Settling – sometimes mixtures
will separate themselves out
over time just due to the
materials having different
densities.
Useful for separating liquids
from solids or liquids with
different densities from each
other.
Separating mixtures
Evaporation – By
heating a liquid
mixture up, the liquid
will evaporate
leaving behind the
solids and substances
that were dissolved in
the liquid.
Useful for separating
solutions.
Separating mixtures
Chromatography – used
to separate different
dissolved substances in a
solution from one another.
Using properties like
electric charge, size, and
how easily things dissolve,
the materials can be
separated.
Chromatography
Chromatography
Separating mixtures
There are many other ways to separate mixtures.
Many of which combine multiple of these
strategies to do it.
Solutions
Solutions are mixtures that
consist of microscopic
particles.
Solutions are formed when
one substance dissolves in
another.
Solutions are almost always
homogeneous mixtures.
Solutions are always liquids
after the substance has
dissolved.
Solutions
A solution always has a substance that is
dissolved and a substance that does the
dissolving.
The substance that is dissolved is the solute.
The substance that does the dissolving is the
solvent.
Kool-aid Mix(solute)
Water(solvent)
Kool-aid(solution)
Solubility
The ability of one
substance to dissolve in
another substance is its
solubility.
There is a limit to how
much solute a solvent
can dissolve.
Solubility
Solubility can be changed dramatically by
changing the temperature of the solvent.
For solid solutes, more solute will dissolve as the
temperature of the solvent goes up.
Solubility graphs
Solubility graphs show how much of a solute will
dissolve in a solvent at a given temperature.
Potassium chloride (solute) in vinegar (solvent)
Solubility graphs
When there is less solute dissolved than a solvent
can hold it is known as an unsaturated solution.
Potassium chloride (solute) in vinegar (solvent)
Solubility graphs
When there is the maximum dissolved for a
specific temperature it is a saturated solution.
Potassium chloride (solute) in vinegar (solvent)
Solubility graphs
When there is more solute dissolved then it is
known as a supersaturated solution.
Potassium chloride (solute) in vinegar (solvent)
Solubility graphs
Supersaturated solutions are made when solute is
dissolved in a heated solvent that is then cooled.
Potassium chloride (solute) in vinegar (solvent)
Supersaturated solutions
Supersaturated solutions are very unstable and
the solute often “falls out” of solution and reforms
crystals. The crystals form on the surfaces of other
crystals or objects in the solution.
Solubility rate
The speed at which
something can dissolve
can also be changed.
Temperature
Mixing
Surface area
• Potassium nitrate
• Sodium nitrate
• Sodium Chloride
Separating mixtures
Extraction – if you have a
substance that can be
dissolved and one that
can’t you can separate
them by dissolving the
one that can be dissolved
and then filtering what’s
left.
Water
Water is known as the
“universal solvent” since
many, many materials
can be dissolved in
water.
Ocean water is basically
a solution of salt in water.
Body fluids are also water
solutions.
Separating Mixtures
Suppose you had a mixture of iron nails, salt and
water…
How would you separate this mixture completely?
Based on which physical properties would you
base your method on?
Separating Mixtures
How would you separate the components in tap
water?
Distillation
A liquid is boiled to produce vapor that is then
condensed again to a liquid
Separating Mixtures
Mixtures
Sample problem
How can a mixture of iron fillings and
aluminum fillings be separated?
1.-Analyze: Plan a problem solving strategy
List the properties of iron and aluminum and
look for something that would be useful in
separating the mixture
Mixtures
Iron:
Metal
Grayish
Not soluble in water
Attracted to a
magnet
Aluminum:
Metal
Grayish
Not soluble in water
Not attracted to
magnets
2.- Solve: Apply the problem-solving strategy.
Make use of a property that differentiates the
metals; use a magnet to attract the iron fillings.
Mixtures
3.-Evaluate: Does the result make
sense?
Because the magnet attracts iron
but not aluminum filings, the iron
would be removed while the
aluminum would be left behind.
Practice Problems
What physical properties could be used to separate iron filings from salt?
Which of the following are homogenous? heterogenous?
1.-Spaghetti sauce 4.-Cough syrup
2.-Glass 5.-Mixture of nitrogen gas
3.-Muddy Water and helium gas
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