What Is a Solution?

1
What Is a Solution?
- Understanding Solutions

• A solution has the same properties throughout. It
  contains solute particles (molecules or ions)
  that are too small to see.

2
What Is a Solution?
- Understanding Solutions

• Solutions can be made from any combinations of
  solids, liquids, and gases.

3
Colloids and Suspensions
- Understanding Solutions

• Colloids and suspensions are mixtures that have
  properties different from those of solutions.

4
Particles in a Solution
- Understanding Solutions

• When a solution forms, particles of the solute
  leave each other and become surrounded by
  particles of the solvent.

5
Effects of Solutes on Solvents
- Understanding Solutions

• At 0ºC, pure water freezes, but water mixed with
  a solute does not. Solutes lower the freezing
  point of a solvent.

Solid (frozen) water
6
Identifying Main Ideas
- Understanding Solutions

• As you read the section What is a Solution?,
  write the main idea in a graphic. Then write
  three supporting details.

Main Idea
A solution is a well mixed mixture that contains
a solventand at least one solute.
Detail
Detail
Detail
Detail
The solvent is the substance present in the
largest amount.
A solute is a substance present in a smaller
amount than the solvent.
A solution has the same properties throughout.
A solution contains particles that are too small
to see.
7
Universal Solvent
- Understanding Solutions

• Click the Video button to watch a movie
  aboutuniversal solvent.

8
Calculating a Concentration
- Concentration and Solubility

• 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.

9
Calculating a Concentration
- Concentration and Solubility

• Practice Problem
• A solution contains 12 grams of solute dissolved
  in 36 grams of solution. What is the
  concentration of the solution?

• 33

10
Solubility
- Concentration and Solubility

• Solubility is a measure of how much solute can
  dissolve in a solvent at a given temperature.

11
Temperature and Solubility
- Concentration and Solubility

• The solubility of the compound potassium nitrate
  (KNO3) varies in water at different temperatures.

12
Temperature and Solubility
- Concentration and Solubility

• Reading Graphs
• At which temperature shown in the graph is KNO3
  least soluble in water?

• KNO3 is least soluble at 0ºC.

13
Temperature and Solubility
- Concentration and Solubility

• Reading Graphs
• Approximately what mass of KNO3 is needed to
  saturate a water solution at 40ºC?

• Approximately 65 g of KNO3 are needed to saturate
  a water solution at 40ºC.

14
Temperature and Solubility
- Concentration and Solubility

• Calculating
• About how much more soluble is KNO3 at 40ºC than
  at 20ºC?

• KNO3 is about twice as soluble at 40ºC as it is
  at 20ºC.

15
Temperature and Solubility
- Concentration and Solubility

• Interpreting Data
• Does solubility increase at the same rate with
  every 20ºC increase in temperature? Explain.

• No the curve shows that solubility increases
  more with each 20ºC increase in temperature.

16
Building Vocabulary
- Concentration and Solubility

• After you read the section, carefully note the
  definition of each Key Term. Also note other
  details in the paragraph that contains the
  definition. Use all this information to write a
  meaningful sentence using the Key Term.

Examples
Key Terms
An unsaturated solution can continue to dissolve
more solute.
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.
A supersaturated solution has more dissolved
solute than is predicted by its solubility at the
given temperature.
solubility
Solubility is a measure of how much solute can
dissolve in a solvent at a given temperature.
saturated solution
A saturated solution contains so much solute that
no more dissolves.
17
Properties of Acids and Bases
- Describing Acids and Bases

• Litmus is an example of an indicator, a compound
  that changes color when in contact with an acid
  or a base.

18
Uses of Acids and Bases
- Describing Acids and Bases

• Acids and bases have many uses around the home
  and in industry.

19
Asking Questions
- Describing Acids and Bases

• Before you read, preview the red headings. In a
  graphic organizer like the one below, ask a what
  question for each heading. As you read, write
  answers to your questions.

What is an acid?
An acid is a substance that tastes sour, reacts
with metals and carbonates, and turns blue litmus
paper red.
What is a base?
A base is a substance that tastes bitter, feels
slippery, and turns red litmus paper blue.
What are uses of acids and bases?
Uses of acids include cleaning products,
fertilizers, and car batteries uses of bases
include cleaning products, baking ingredients,
and cement manufacturing.
20
Acids and Bases in Solution
- Acids and Bases in Solution

• The table lists some commonly encountered acids
  and bases.

21
Strength of Acids and Bases
- Acids and Bases in Solution

• Strong acids and weak acids act differently in
  water. Hydrochloric acid is a strong acid. Acetic
  acid is a weak acid.

22
The pH Scale
- Acids and Bases in Solution

• A low pH tells you that the concentration of
  hydrogen ions is high. In contrast, a high pH
  tells you that the concentration of hydrogen ions
  is low.

23
Acid-Base Reactions
- Acids and Bases in Solution

• A reaction between an acid and a base is called
  neutralization. An acid-base mixture is not as
  acidic or basic as the individual starting
  solutions.

24
Acid-Base Reactions
- Acids and Bases in Solution

• Each salt listed in this table can be formed by
  the reaction between an acid and a base.

25
Previewing Visuals
- Acids and Bases in Solution

• When you preview, you look ahead at the material
  to be read. Preview Figure 21. Then write two
  questions that you have about the diagram in a
  graphic organizer like the one below. As you
  read, answer your questions.

Neutralization
Q. What is a neutral solution?
A. A neutral solution is one that has a pH close
to 7.
Q. What is neutralization?
A. Neutralization is a reaction between an acid
and a base.
26
pH
- Acids and Bases in Solution

• Click the Video button to watch a movie about pH.

27
What Is Digestion?
- Digestion and pH

• Chemical digestion breaks large molecules into
  smaller ones.

28
pH in the Digestive System
- Digestion and pH

• Foods are exposed to several changes in pH as
  they move through the digestive system.

29
Sequencing
- Digestion and pH

• Sequence is the order in which a series of events
  occurs. As you read, make a flowchart that shows
  the sequence of changes in pH as food moves
  through the digestive system.

pH During Digestion
At a pH near 7, enzymes in the mouth start to
break down carbohydrates.
At a pH near 2, stomach enzymes break down
proteins.
At a pH near 8, enzymes in the small intestine
complete the breakdown of carbohydrates, fats,
and proteins.
30
Graphic Organizer

Solutions
are made of
Solutes
Solvents
dissolve in
dissolve to form
such as
Water
Ions
Molecules
do not conduct
conduct
Electricity