Solutions, Acids and Bases

1
Solutions, Acids and Bases

• Chapters 23 and 25

2
What is a Solution?

• A solution that has the same composition, color,
  density, and even taste throughout.
• A Solution can be a solid liquid or gas.
• Solid Steel, Brass, Bronze
• Liquid Can you think of some?
• Gas the air you breathe

3
Solute and Solvent

• Solute is the substance that is being dissolved.
• Solvent is the substance doing the dissolving.
• How can we remember the difference between the
  two?

4
Dissolving

• Water is what we call a polar molecule. That
  means that water has a positive and a negative
  end.
• When we dissolve something in water the water
  molecules are attracted to the solute by a
  positive or negative attraction.
• Eventually, the water pulls the solute apart and
  into the rest of the solution.

5
How do we mix different phases?

• Gases into liquids
• A gas must be cooled or compressed to be
  dissolved into a liquid
• Solids into solids
• All solids must be changed to a liquid and then
  combined. The new solution is then cooled and
  formed into the new substance.

6
How do we change the speed at which something
dissolves?

• Surface Area
• If you increase the surface area you will
  increase the rate of dissolving.
• Increase the surface area by breaking up the
  substance.
• Pg. 710
• Temperature
• If you increase the temperature then you will
  increase the rate of dissolving.
• For a gas you must decrease the temperature.
• Pressure
• Only for gases if you increase the pressure you
  will increase the rate of dissolving.
• Agitation
• Stirring a solution increases the rate of
  dissolving.

7
Solubility

• Solubility is the maximum amount of a solute that
  can be dissolved in a given amount of solvent at
  that temperature.
• The amount that can be dissolved depends on the
  nature of the substance.
• Solubility tables will tell you the temperature
  and the amount in grams per 100 grams of water.
• See table 2 on pg 719 and table 3 on pg 720

8
Types of Solutions

• Saturated a solution that contains all it can
  hold at a given temperature.
• Unsaturated a solution that can dissolve more
  at a given temperature.
• Supersaturated a solution that contains more
  that it is supposed to be able to hold. See page
  721

9
Solubility Curves

• A solubility curve shows the temperature compared
  to the solubility.

10
More Solubility Curves
11
Particles in Solution

• What do we call atoms that are positively or
  negatively charged?
• The solutions that contain ions are called
  electrolytes.
• Electrolytes will conduct electricity.
• The more ions that are in a solution the stronger
  the electrolytic behavior.

12
What happens to the freezing point or boiling
point of water when we add a solute?
13
Properties of Acids

• An acid is a substance that produces positive
  hydrogen ions (H) in a water solution.
• The more H that are present the stronger the
  acid is.
• All acids
• Taste sour
• Are corrosive
• React with indicators to produce predictable
  changes in color

14
Common Acids

• Citric Acid Found in many fruits
• Lactic Acid found in all milk products
• Hydrochloric Acid Stomach acid
• See pg 767 for another list of acids and their
  uses.

15
Properties of Bases

• Base any substance that forms hydroxide ions,
  OH-, in a water solution. The more OH- the
  stronger the base is.
• Bases are the complement to or opposite of Acids.
  They share some of the same properties but have
  their own characteristics.
• All Bases
• Are crystalline in their un-dissolved state.
• In solution they are slippery and have a bitter
  taste.
• Corrosive
• React with indicators to produce changes in color.

16
Common Bases

• Most bases are used as cleaning products in your
  home.
• Ammonia
• Sodium Hydroxide
• Others are used as laxatives or antacids.
• Magnesium Hydroxide (Milk of Magnesia)
• Aluminum Hydroxide
• See pg 769 for more examples.

17
Strong and Weak Acids and Bases

• We can tell the difference between an acid and a
  base by using litmus paper.
• Red is acid
• Blue is base
• We can tell how strong an acid or base is by
  passing an electric current through it. The
  stronger an acid is the more electric current
  will pass through it.
• Concentration of an acid or base does not mean
  that is strong or weak. There is simply more or
  less of it.

18
pH of a Solution

• The pH of a solution is the measure of the number
  of positive Hydrogens (H) in the solution.
• The greater the concentration of H the lower the
  pH is and the more acidic the solution is.
• To indicate pH, a scale ranging from 0 to 14 has
  been devised. See pg 774 Figure 9 for an example.
• On this scale 0 is extremely acidic and 14 is
  extremely caustic (base).
• 7 is neutral pure water at 25 degrees Celcius

19
(No Transcript)