A mixture is a combination of two or more substances that are not chemically combined.
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Transcript of A mixture is a combination of two or more substances that are not chemically combined.
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A mixture is a combination of two or more substances
that are not chemically combined
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Two or more materials together form a mixture
if they do not react to form a compound.
Cheese and tomato sauce do not react when they are used
to make a pizza
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Substances in a mixture retain their
identity• Because no chemical
change occurs, each substance in a mixture has the same chemical makeup
it had before the mixture formed.
• Each substance in a mixture keeps its identity
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Mixtures can be physically separated
• Since the identities of the substances in a mixture do not change, they can be physically separated.
• Remember, compounds can be broken down only
through chemical changes.
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Common techniques for
separating mixtures
•Distillation•Magnets
•Centrifuge•Filtering
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Distillation• Distillation is a process that separates a mixture
based on the boiling points of the components• Examples of distillation
are:– Pure water being
distilled from a saltwater mixture
– Separate crude oil into gasoline and kerosene
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• Oil Refineries use distillation to separate
gasoline and natural gas from crude oil
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Magnetism• A magnet can be used to separate a mixture of substances in which the
magnet will attract.• A mixture of aluminum
and iron can be separated with a magnet. Iron is
attracted to the magnet, but aluminum is not.
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Centrifuge
•This machine separates mixtures according to
the densities of the components
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• Density is used to separate a mixture of
ripe and unripe cranberries. Ripe
cranberries float in water, but unripe
cranberries sink. During harvesting, cranberry bogs are flooded, and
the floating cranberries are skimmed from the
water.
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Filtration•If a mixture contains
two substances and one of those
substances is soluble, then dissolve the
soluble substance, pour it into a filter and
trap the un-soluble substance in the filter.
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Air Filters
• Filters are used in many different ways. Some separate
liquids, some separate solids suspended in air.
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Components of a mixture do not have a definite
ratio• The components of a mixture do not need to
be combined in a definite ratio.
• Air is a mixture composed mostly of nitrogen and
oxygen, and water vapor. Some days the air has more water vapor, or is
more humid, than on other days.
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Mixtures vs Compounds
MixturesMixtures CompoundsCompoundsComponents are
elements, compounds, or both
Components are elements
Components keep their original
properties
Components lose their original
properties
Separated by physical means
Separated by chemical means
Formed using any ratio of components
Formed using a set ratio of components
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The Liberty Bell is a mixture of 70 % copper, 25 %
tin, and small amounts of lead,
zinc, arsenic, gold, and silver.
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• A solution is a mixture that appears to be a single
substance but is composed of particles of two or more substances
that are distributed evenly amongst each other
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• Solutions are often described as homogeneous mixtures because they have the same
appearance and properties throughout the mixture.• The process in which particles of substances
separate and spread evenly throughout a mixture is
known as dissolving.
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• In solutions, the solute is the substance that is
dissolved, and the solvent is the substance in which
the solute is dissolved.• A solute is soluble, or
able to dissolve, in the solvent
• A substance that is insoluble, or unable to
dissolve, forms a mixture but it is not a solution.
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What did the compound say to the solution?
You’re all mixed up!!You’re all mixed up!!
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• Salt water is a solution• Salt is soluble in water, meaning
that salt dissolves in water• Salt is the solute and water is
the solvent• When two liquids or
two gases form a solution, the substance with the greater volume
is the solvent.
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• Many substances are soluble in water, including
salt, sugar, alcohol, and oxygen.
• Water does not dissolve everything, but it dissolves
so many different solutes that it is often called the
….universal solvent.
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• Tap water, soft drinks, gasoline,
and many cleaning supplies are liquid
solutions.• However, solutions
may also be gases, such as air
•Some solutions are solids, such as
steel
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Alloys• Alloys are solid solutions of
metals or nonmetals dissolved in metals.
• Brass is an alloy of the metal zinc dissolved in
copper• Steel is an alloy made of the nonmetal carbon and other elements dissolved
in iron
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Examples of Different Examples of Different States in SolutionsStates in Solutions
Gas in gas Dry air (oxygen in nitrogen)
Gas in liquid Soft drinks (carbon dioxide in water)
Liquid in liquid Antifreeze (alcohol in water)
Solid in liquid Salt water (salt in water)
Solid in solid Brass (zinc in copper)
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Particles in solutions Particles in solutions are extremely smallare extremely small
• The particles in solutions are so small that they
never settle out, nor can they be filtered
out of these mixtures.
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Concentrated or Dilute???
• A measure of the amount of solute dissolved in a
solvent is concentration• If two solutions have the
same amount of solvent, then the solution which
contains less solute is dilute, while the solution
which contains more solute is concentrated.
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Is the solution Is the solution saturated????saturated????
• A solution that contains all the solute it can hold at a given
temperature is said to be saturated.
• An unsaturated solution contains less solute than it can
hold at a given temperature.• More solute can dissolve in an
unsaturated solution.
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How much solute can dissolve?
• The solubility of a solute is the amount of solute needed to make
a saturated solution using a given amount of
solvent at a certain temperature
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• For example, if you add too much sugar to a
glass of lemonade, not all of the sugar can dissolve.
• Some of the sugar collects on the bottom of
the glass• To determine the
maximum amount of sugar that can dissolve, you would need to know
the solubility of sugar.
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Solubility of Different Substances
The solubility of most solids, increases as the temperature gets higher. Thus, more solute can dissolve at higher temperatures. However, some solids, such as Cerium Sulfate, are less soluble at higher temperatures.
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• Unlike the solubility of most solids in liquids, the solubility of gases in liquids decreases as the temperature is raised
Did you know……..
Because less gas dissolves in a liquid if the temperature is raised, fish can
suffocate when aquarium water becomes too warm—there may not be enough oxygen dissolved in the water.
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What affects how quickly solids dissolve in liquids?
• Several factors affect how fast the solid will dissolve• Three methods used to
make a solute dissolve faster are:
• Mixing• Heating
• Crushing
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Mixing• Mixing by stirring or
shaking causes the solute particles to
separate from one another and spread
out more quickly among the solvent
particles
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Heating• Heating causes particles to move more quickly. The solvent particles can separate the solute particles
and spread them out more quickly.
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Crushing
• Crushing the solute increases the amount of
contact between the solute and the solvent. The particles of solute mix with the solvent
more quickly.
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A suspension is a mixture in which
particles of a material are
dispersed throughout a
liquid or gas but are large enough that they settle
out.
When you stop shaking a snow globe, the snow particles settle to the bottom of the globe.
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The particles in a suspension are
insoluble, so they do not
dissolve in the liquid or gas.
Suspensions are often described as heterogeneous
mixtures because the different components are
easily seen.
Italian salad dressing is an Italian salad dressing is an example of a suspensionexample of a suspension
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•The particles in a suspension are fairly large, and they
scatter or block light, this makes a suspension difficult
to see through.•The particles are too heavy
to remain mixed without being stirred or shaken
• If a suspension is allowed to sit undisturbed, the particles
will settle out.
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• Blood is a suspension.• The suspended particles, mainly red
blood cells, white blood cells, and platelets, are actually suspended in a
solution called plasma.• Plasma is 90% water and 10%
dissolved solutes, including sugar, vitamins, and proteins.
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• Dirty air is a
suspension that could damage a
car’s engine. • The air filter in a car separates dust
from air to keep the dust from
getting into the engine.
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Shake Well Before Use
• Many medicines, such as remedies for upset stomach, are suspensions. The directions on the label instruct you to
shake the bottle well before use.
• Why must you shake the bottle?
• What problem could arise if you don’t?
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Colloids•A colloid is a mixture in
which the particles are dispersed throughout but are not heavy enough to
settle out.The particles in a colloid are relatively small and
are fairly well mixed.
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• Milk, mayonnaise, stick deodorant—even the gelatin and whipped
cream are colloids.• The materials that
compose these products do not separate between
uses because their particles do not settle
out.
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• Although the particles in a colloid are much smaller than the particles in a suspension, they are still large enough to
scatter a beam of light shined through the colloid.
• Unlike suspension, a colloid cannot be separated by
filtration The particles are small enough to pass through
a filter.