What Is a Solution?
• Solutions can be made from any
combinations of solids, liquids, and gases.
Particles in a Solution
• When a solution forms, particles of the
solute leave each other and become
surrounded by particles of the solvent.
Colloids and Suspensions
• Colloids and suspensions are mixtures
that have properties different from those of
solutions.
Effects of Solutes on Solvents
• At 0ºC, pure water freezes, but water
mixed with a solute does not. Solutes
lower the freezing point of a solvent.
Solid (frozen) water
Liquid water solution
Assessment
1. What is a solution?
2. Suppose you mix food coloring in water
to make it blue. Have you made a
solution or a suspension? Explain.
3. How are solutions different from colloids
and suspensions?
Assessment
1. What happens to the solute particles when a
solution forms?
2. What affects do solutes have on a solvent’s
freezing and boiling points?
3. Why is the temperature needed to freeze ocean
water lower than the temperature needed to
freeze the surface of a freshwater lake?
4. Why does salt sprinkled on icy roads cause the
ice to melt?
CONCENTRATION
Definition: The amount of a substance per
defined space. Concentration usually is
expressed in terms of mass per unit volume.
Calculating a Concentration
• To calculate the concentration of a solution,
compare the amount of solute to the amount
of solution and multiply by 100 percent.
• For example, if a solution contains 10 grams
of solute dissolved in 100 grams of solution,
then its concentration can be reported as 10
percent.
Try This
• A solution contains 12 grams of solute
dissolved in 36 grams of solution. What
is the concentration of the solution?
Solubility
• Solubility is a
measure of how
much solute can
dissolve in a solvent
at a given
temperature.
Key Terms:
Examples:
unsaturated solution
An unsaturated solution can continue to dissolve
more solute.
supersaturated
solution
A supersaturated solution has more dissolved solute
than is predicted by its solubility at the given
temperature.
dilute solution
A dilute solution is a mixture that has only a little
solute dissolved in a certain amount of solvent.
concentrated solution
A concentrated solution is one that has a lot of
solute dissolved in the same amount of solvent.
Solubility is a measure of how much solute can
dissolve in a solvent at a given temperature.
A saturated solution contains so much solute that no
more dissolves.
solubility
saturated solution
Assessment
1. What is concentration?
2. What quantities are compared when the
concentration of a solution is measured?
3. Solution A contains 50 g of sugar.
Solution B contains 100g of sugar. Can
you tell which solution has a higher sugar
concentration? Explain.
Assessment
1. What is solubility?
2. How can solubility help identify a
substance?
3. What are the three factors that affect
solubility?
Acid:
A substance that
releases H+ ions in
an aqueous solution
“aqueous” means: water
Characteristics of Acids:
 Acids have a sour taste
 Acids react with metals
 Acids contain Hydrogen
 Many are poisonous and
corrosive to skin
H
Strong Acids
(break down completely to give off many H+ ions)
Weak Acids
(only partially breaks down, gives less H+)
Common Acids:
Strong Acids
The Formula
Sulphuric acid
Hydrochloric acid
Hybrobromic acid
Hydroiodic acid
Nitric acid
Perchloric acid
H2SO4
HCl
HBr
HI
HNO3
HClO4
All others considered Weak (examples)
Weak Acid
The Formula
Acetic acid (vinegar)
Carbonic acid
HC2H3O2
HCO3
Base:
A substance that
releases OH- ions in
an aqueous solution
Characteristics of Bases:
 Bases usually taste bitter
 Bases feel slippery
 Bases contain hydroxide ions
 STRONG bases are also poisonous
and corrosive to skin
OH
Common Bases:
Strong Bases
The Formulae
Lithium hydroxide
Sodium hydroxide
Potassium hydroxide
Rubidium hydroxide
Caesium hydroxide
Barium hydroxide
Calcium hydroxide
Strontium hydroxide
LiOH
NaOH
KOH
RbOH
CsOH
Ba(OH)2
Ca(OH)2
Sr(OH)2
(Hydroxides of Group 1 and Group 2 Metals
are STRONG)
All others are WEAK
Some bases (VERY FEW)
don’t have OHMost commonly:
ammonia NH3
Section 3 Assessment
1. What are four properties of acids? Of
bases?
2. How can you use litmus paper to
distinguish and acid from a base?
3. How might you tell if a food contains an
acid as one of its ingredients?
Section 3 Assessment
1. What are three practical uses of an acid?
Of a base?
2. Where are you most likely to find acids
and bases in your own home? Explain.
3. Why is it wise to wear gloves when
spreading fertilizer in a garden?
Salts
Reactions between
acids and bases
When and acid and a base
react with each other, the
characteristic properties of
both are destroyed. This is
called neutralization.
Reactions between
acids and bases
General formula for acid base reaction:
Acid + Base → H2O + Salt
“Salt” means any ionic
compound formed from
an acid/base reaction NOT JUST
NaCl !!
Neutralization
HCl + NaOH → H2O + NaCl
acid
base
water
salt
Neutralization
Another Example
HNO3 + KOH → H2O + KNO3
H NO3
acid
K OH
base
water
salt
pH
pH stands for “potential
hydrogen” and is a measure
of how many H+ ions there
are in solution.
The MORE H+ there are, the
LOWER the pH will be.
Indicators
An indicator is a compound
that will change color in the
presence of an acid or base
Red Litmus-Turns blue in base
Blue Litmus-Turns red in acid
Universal indicator (pH paper)
Used for the full pH range
Phenolphthalein-Turns pink
in base
pH Scale
Shows the range of H+
concentrations
High H+ concentration
Low H+ concentration
Section 4 Assessment
1. What does a substance’s pH tell you?
2. If a solution has a pH of 6, would the
solution contain more or fewer hydrogen
ions (H+) than an equal volume of
solution with a pH of 3?
Digestion and pH