Solutions

1
Solutions

• Mr. V. Perez
• Grade 6 Science

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Solutions

• A solution is a mixture of particles that
• Are so small that they cannot be seen with a
  microscope
• Will not settle to the bottom of a container
• Will remain constantly and uniformly mixed
• Solute is the substance being dissolved
• Solvent is the substance in which the solute is
  dissolved
• Water is called the Universal Solvent because
  many substances dissolve in water.
• Ex saltwater, sugar water, Kool-Aid, club soda,
  homogenized milk, iced-tea, lemonade, grape
  juice, chocolate milk, etc.
• Identify the solute and solvent in the following
  examples

1. Sea Water 2. Iced-Tea 3. Water Vapor
Salt (solute), Water (solvent) Iced-Tea
Powder (solute), Water (Solvent) Water
(solute), Air (solvent)
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Solutions

• When a solid dissolves in a liquid the solid is
  the solute and the liquid is the solvent
• When a liquid dissolves in another liquid, the
  substance present in the LARGER amount is usually
  called the solvent
• Water vapor in the air is an example of a liquid
  dissolved in a gas
• Here are some solutions and their states of
  matter
• Ex Sugar water Sugar (solute), Water (solvent)
• This is an example of a solid dissolved in a
  liquid
• Ex Soda Carbon Dioxide Gas (solute), Water
  (solvent).
• This is an example of a gas dissolved in a
  liquid.
• Ex Lemonade Lemon Juice (solute), Water
  (solvent)
• This is an example of a liquid dissolved in a
  liquid

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How Substances Dissolve

• Water is called the Universal Solvent because
  many substances dissolve in water.
• The dissolving of a solid in a liquid occurs at
  the surface of the solid
• How does a sugar cube dissolve in water?
• Water molecules are constantly moving
• Water molecules cluster around the sugar
  molecules (with the waters negative ends
  attracted to the positive ends of the sugar)
• The water molecules pull the sugar into the
  solution and mix together evenly forming the
  solution
• Ex Sports drinks, fruit drinks, iced-tea,
  Kool-Aid, hot-chocolate, chocolate milk, etc

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How Much Can Dissolve?

• Solubility is the maximum amount of a solute that
  can be dissolved in a given amount of solvent at
  a given temperature
• Soluble means able to dissolve
• Ex Club Soda Carbon Dioxide is soluble because
  it dissolves in water. (It is a gas dissolved in
  a liquid.)
• Ex Salt Water Salt is soluble because it
  dissolves in water. (It is a solid dissolved in a
  liquid)
• Insoluble means not able to dissolve
• Ex Sand and Water Sand is insoluble because
  it does not dissolve in water, it sinks to the
  bottom of the glass

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Three Ways to Change the Rate of Dissolving?

• Stirring Stirring a solution will make a solute
  dissolve faster because the solute particles are
  able to squeeze between solvent particles
• A sugar cube will dissolve more rapidly in water
  when the water is stirred
• 2) Heating (Temperature Change) Heat causes
  the molecules of a solute to dissolve more
  rapidly because they move faster and further
  apart
• A sugar cube will dissolve more rapidly when it
  is heated. Higher temperatures dissolves
  faster.
• 3) Crushing (Smaller Particles) The smaller the
  particle size, the quicker it will dissolve in a
  liquid
• A sugar cube will dissolve more rapidly when it
  is crushed because more surface area touches water

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Three Ways to Change the Rate of Dissolving?
Stirring
Heating (Temperature)
Crushing (Particle Size)
Not crushed
Crushed
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How Do Solutes Affect Freezing Point?

• Freezing Point Depression is the lowering of the
  freezing point of a liquid solvent by adding
  solute
• The Freezing Point of water
• is 0C (32F)

• In this diagram, the salt added to the water
  decreases the freezing point of the water by 2 C
  (from 0 Celsius to -2 Celsius)
• Water will no longer freeze at 0C (32F), it
  freezes at -2C
• In winter, salt is put on sidewalks so water will
  change from a liquid to ice at much lower
  temperatures. People will not fall!

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How Do Solutes Affect Boiling Point?

• Boiling Point Elevation is raising the boiling
  point of a liquid solvent by adding solute
• The Boiling Point of water is 100C (212F)

• In this diagram, for every 5 grams of salt added
  to the water, the boiling point of the water
  increases by 1 Celsius
• Water will no longer boil at 100Celsius (212F),
  it boils at 104Celsius
• It will take the water longer to boil (but the
  food will cook at a higher temperature)

10
Concentration

• A concentrated solution is one in which a large
  amount of solute is dissolved in the solvent
• A dilute solution is one that has a small amount
  of solute in the solvent
• Ex You add one teaspoon of lemon juice to
  water, and your friend adds four teaspoons of
  lemon juice to the same amount of water. What is
  the difference between the two solutions?
• Your glass of lemonade is dilute because it has
  less concentrate (with only one teaspoon of lemon
  juice)
• Your friends glass of lemonade is concentrated
  because it has more concentrate (with four
  teaspoons of lemon juice compared to one
  teaspoon)
• Why? Because your friends lemonade has more
  solute (lemon juice) dissolved in the solvent
  (water)

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Precise Concentrations

• How much real fruit juice is there in a boxed
  drink of fruit juice?
• You can tell exactly how much fruit juice there
  is by looking at the percentage (by volume) of
  the concentrate

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Types of Solutions

• An Unsaturated Solution is any solution that can
  dissolve more solute at a given temperature
• A Saturated Solution is a solution that contains
  all of the solute it can hold at a given
  temperature
• A Supersaturated Solution is one that contains
  more solute than a saturated solution at the same
  temperature.
• When some saturated solutions are heated, they
  can hold more solute than normal. When the
  saturated solution cools down, it has too much
  solute so it is called a supersaturated
  solution. The additional solute (that was added
  at the higher temperature) crystallizes into a
  solid.
• What can you do to turn an saturated solution
  into an unsaturated solution?
• You can heat the solution (to make room for more
  solute).