Mixtures and Solutions

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Mixtures and Solutions

• Diane Gioia
• Bells Crossing Elementary

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What is a mixture?

• A mixture is two or more substances that are
  mixed together but not chemically combined.
• The substances in a mixture each keep their own
  properties, and they can be separated into their
  original form.
• A bag of snack mix can be separated into raisins,
  walnuts, peanuts, etc.

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Examples of mixtures

• Vegetable salad
• Fruit salad
• Mixture of sand, water, and marbles
• Mixture of sand and iron filings

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• Mixtures can be separated based on physical
  properties.
• Blood is a mixture of proteins, sugar, oxygen,
  carbon dioxide, and other substances. The
  different substances in blood can be separated
  based on their densities.

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What are Solutions?
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Solutions

• Solutions are composed of substances that mix so
  completely that they cannot be distinguished as
  separate substances.
• They can, however, be easily separated back into
  the separate substances.
• A solution is usually a mixture of a solid that
  dissolves completely in a liquid.
• Ex. Sugar in water

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Solutions

• A solution is a special kind of mixture.
• The substances in a solution dissolve, or
  separate into their most basic particles.
• The particles of one substance are spread evenly
  through another.
• The substances in a solution can be solids,
  liquids, or gases.

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Examples of a Solution

• Carbon dioxide bubbles in a soda.
• Carbonated water mixed with lemonade is a
  solution of solids, liquids, and gases.
• Lemon juice, water and sugar crystals. Sugar is
  the solid, lemon juice is the liquid dissolved
  together in water.

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What makes up a solution?

• In a solution, the substance that dissolves is
  called the solute.
• The solvent is the substance in which the solute
  is being dissolved.
• Sugar is the solute and water is the solvent.
• Water is considered the universal solvent.

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True or False?

• All solutions are mixtures, but not all mixtures
  are solutions.

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TRUE!

• That's a true statement. All solutions are
  mixtures. They are defined as homogeneous
  mixtures. Solutions might include salt water,
  soda water, or even metal alloys. Not all
  mixtures are solutions. If you mix sand and
  water, you might have a liquid involved, but that
  doesn't make it a solution. A mixture that
  includes sand and water would be defined as a
  heterogeneous mixture. The parts are not
  distributed evenly throughout the system.

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Why is the Venn Diagram combined with the
solution circle within the mixture circle?

• Explain in your journal. Summarize with class.

MIXTURES
Mud chex mix Fruit salad
SOLUTIONS
Salt water lemonade soda
p.s. Mud is a special mixture called a
suspension. The particles suspend in the water.
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Can you make a list of Mixtures?
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How many Solutions can you list?
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How do we separate mixtures and solutions?

• There are many ways to separate mixtures and
  solutions.
• The method depends on the properties of the
  different materials in the mixture.

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Make a Lotus
How can you separate the materials in mixtures
and solutions?
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SIFTING

• One way to separate the larger materials from the
  smaller ones is by sifting.
• Sifting allows smaller materials to pass through
  holes leaving the larger materials behind.
• How would you use sifting to separate marbles,
  safety pins, sand, and salt?

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Magnetic Attraction

• After you have separated the sand and salt from
  the bigger materials using sifting you can use
  a magnet to pick up the objects made out of
  certain metals such as paper clips and safety
  pins.
• Could you use a magnet to separate
• Sand, marbles, and plastic beads?
• Why or why not?

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Floatation

• Floatation is using a liquid to separate
  materials of different densities.
• A material that is less dense will float on a
  material that is more dense.
• Plastic beads are less dense than marbles.
• How would you separate marbles from plastic beads
  using floatation?

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Filtration

• You can also separate solutions by filtering
  them. Filtration is separating solids from
  liquids by passing a mixture through a filter.
• Salt dissolves in water while sand does not.
• How could you separate salt and sand using water
  and a filter?

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Evaporation

• After you have filtered out the sand from the
  solution of salt water, you can use evaporation
  to separate the salt from the water.
• When water evaporates from the mixture, solid
  salt particles will be left behind.
• How would evaporation naturally separate dirt
  from water in a mud puddle?

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Chromatography

• Chromatography separates solutions by dissolving
  them in special liquids.

For example, chromatography can be used to
separate substances such as pigments in a leaf
like in the picture. The police department uses
chromatography to separate and identify all kinds
of substances.
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How can we make a solution more or less
concentrated?

• The concentration of the solution is a measure of
  the amount of solute compared to the amount of
  solvent.
• If the amount of solute is small compared to the
  amount of solvent, the solution is said to be
  dilute.
• If the amount of solute is large compared to the
  amount of solvent, the solution is said to be
  concentrated.

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Concentrations

• For example, if you took one gram of salt and
  added it to 100 grams of water, the solution is
  dilute.
• If the same amount of water has 30 grams of salt,
  the solution is concentrated.

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Rate of Dissolving

• You know that salt easily mixes with water by
  dissolving in it. But did you know that salt can
  dissolve at different rates?
• The temperature of the water, the size of the
  salt particles, and how you stir the solution are
  factors that affect how quickly the salt
  dissolves.

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Temperature

• Temperature affects the rate of dissolving in a
  solution.
• The particles of a substance are always moving.
  When heat is added, the particles move faster
  making it dissolve faster in a liquid.
• Think about adding sugar to ice tea vs. hot tea.
  Which one dissolves faster?

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Particle Size

• Another factor that affects the rate of
  dissolving is particle size. The smaller the
  solute particles are, the faster they dissolve.
• If you have ever made a cup of hot chocolate, you
  dissolved powder into milk.
• If you put a piece of a chocolate bar in the
  milk, it would take a longer time to dissolve.

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Stirring

• Stirring also affects the rate of dissolving.
• When adding particles to a liquid, you stir or
  shake the liquid. This action makes the solute
  dissolve more quickly.
• What happens if you pour a drink mix into a
  container without stirring?

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Solubility

• Solubility 415

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Chemical ReactionsLet's start with the idea of
a reaction. In chemistry, a reaction happens when
two or more molecules interact and something
happens. That's it. What molecules are they? How
do they interact? What happens? Those are all the
possibilities in reactions. The possibilities are
infinite.
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A few key points

• A chemical change must occur. You start with one
  compound and turn it into another. That's an
  example of a chemical change. A steel garbage can
  rusting is a chemical reaction. That rusting
  happens because the iron (Fe) in the metal
  combines with oxygen (O2) in the atmosphere.

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• When a refrigerator or air conditioner cools the
  air, there is no reaction. That change in
  temperature is a physical change. Nevertheless, a
  chemical reaction can happen inside of the air
  conditioner.

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Another chemical reaction
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How is a chemical change different from a mixture?

• A compound is a type of matter made of a
  combination of elements. In a compound, two or
  more elements are combined chemically.
• Water is made up of two atoms of hydrogen and one
  atom of oxygen.
• H20

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• The proportion of hydrogen and oxygen atoms in
  water is always the same.
• If the proportion of elements in a compound is
  changed, a new compound is formed.
• Both water and hydrogen peroxide are made of
  hydrogen and oxygen atoms.
• However, a molecule of hydrogen peroxide contains
  two hydrogen atoms and two oxygen atoms.
• Hydrogen peroxide is NOT like water and you
  should not drink it.
• H2O2

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Separating Compounds

• When elements combine chemically, they form
  compounds with properties that are different from
  the properties of the individual elements.
• These elements cannot be easily separated like in
  a mixture.

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• A chemical change occurs when atoms link together
  in new ways to create a substance different from
  the original substance. This is a chemical
  reaction.

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Signs of a Chemical Change

• Changes color
• Forms tarnish
• Releases gas
• Forms a precipitate
• Releases energy

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Matter and its Properties

• Full video 1706
• ( a good review
• or watch segment on chemical reactions
  153)