Unit 1 Section C

1
Unit 1 Section C

• Solubility

2
C.1-Solubility of Solids in Water

• Solubility is a measure of how much of a
  substance will dissolve in a given amount of
  water at a certain temperature.
• Different substances have different solubilities.

3
What is a saturated solution?

• A saturated solution has dissolved as much of the
  solute as it can. It cant dissolve any more,
  its full!

4
Does the solubility of a substance ever change?

• NO. No amount of stirring will increase the
  solubility of a substance (if the temperature
  remains constant)

5
What is a solubility curve?

• A graph that shows how solubility changes with a
  change in temperature.
• In general, a substance is more soluble at higher
  temperatures.

6

• Solubility curve for 3 compounds.

7
(No Transcript)
8
How is an unsaturated solution different than a
supersaturated solution?
9
What happens to a saturated solution if you
decrease the temperature?

• As the temperature drops, the solution will
  become supersaturated and crystals will begin to
  form.
• If you would increase the temp. the solution
  would become unsaturated and able to dissolve
  more solute.

10
What happens to a supersaturated solution if you
increase the temperature?

• As you increase the temperature, more solute will
  be able to dissolve and it will become saturated,
  and eventually unsaturated.

11
C.2 Use the solubility curve to answer
questions 1,2 and 3 p.56
12
C.4 Dissolving Ionic Compounds

• What is a polar molecule?
• A molecule in which the electrical charge is not
  evenly distributed. This creates a slightly ()
  end and a slightly () end.
• Water is polar.

13
A molecule of water.

• Oxygen is slightly negative
• The hydrogen atoms are slightly positive
• Why?
• The electrons are more concentrated at the O end.

14
Properties of polar molecules

• Are attracted to other polar molecules
• Are attracted to other electrically charged
  particles such as ions.
• Water will pull apart ionic compounds atom by
  atom and dissolve them.

15
Water dissolving an ionic compound.
16
What factors influence how well an ionic
substance will dissolve?

• The strength of the ionic bonds. Stronger are
  harder to dissolve.
• Properties of the solvent and solute both
  determine how well it will dissolve.

17
Use fig. 1.39 to answer the questions.

• 1. What force is holding the ionic crystal
  together?
• Why do the water molecules interact with the
  ions?
• How are dissolved Cl and Na ions different from
  each other?

18
V. Sec C.6 Ways to describe solutions

• Concentration is a measure of the amount of
  solute dissolved in the solvent
• Percent values gives the of solute in the
  solution. Ex. 5 NaCl means 5of the total mass
  of the solution is NaCl
• ppm or ppb parts per million (or billion) is
  used to express very small concentrations

19
B. What is a safe level of nitrates in drinking
water?

• Nitrate (NO3-) is an anion that gets in water
  from fertilizers.
• Max limit to be safe for drinking is 10 ppm

20
(No Transcript)
21
VI. Section C.7 Describing solution
concentrations

• Read sample problems 1 and 2 then complete
  questions 1 5 on page 64.

22

• 1. a. sucrose b. water
• 2. a. 8.5 b. 9.09
• 3. a.i 4.0ppm ii. 294 ppm
• b. 85000 ppm, 90900 ppm
• 4. a. 31 b. 15
• 5. Add 38 g of KNO3 to 100 g of 25 degree Celcius
  water.

23
VII. Section C.8 Inappropriate Heavy-Metal Ion
Concentrations

• 1. Read C.8 and complete the Reading Guide
  (handout)
• 2. Define
• Green Chemistry
• Heavy Metal Ions -

24
3. What are uses of lead?

• Making water pipes (not done any more)
• Pottery
• Automobile electrical storage batteries
• Solder
• Pesticides
• Paint
• Leaded gasoline (tetraethyl lead) not any more!

25
What are uses of mercury?

• Good electrical conductor light switches
• Thermometers
• Mercury-vapor street lamps
• Fluorescent bulbs
• Some paints
• Eliminate fungi, bacteria and agricultural pests
• Making felt hats (mad as a hatter!)

26
(No Transcript)
27
(No Transcript)
28
Section C.9 Inappropriate pH Levels

• Define these terms
• pH-
• Alkaline
• Acid
• Base

29
B. How is a substance with a pH of 3 different
than a pH of 4? 9?

• A pH of 3 is acidic (0 6.9)
• A pH of 4 is also acidic, but not as strong (0 is
  strongest acid)
• A pH of 9 is basic ( 7.1 14)
• 7 is neutral

30
(No Transcript)
31
C D How do acid and bases behave in solution?

• Acids produce H ions when placed in water
• Stronger acids produce more ions
• Bases produce OH- ions in water
• Stronger bases produce more OH-

32
E. Name the acid or base found in the following

• Battery fluid
• Soft drinks
• Liquid soap
• cement

• Sulfuric acid
• Carbonic acid
• Potassium hydroxide
• Calcium hydroxide

33
F. What is the pH of the following?

• 1. ammonia
• 2. stomach acid
• 3. pure water
• 4. oranges

• 12 (basic)
• 1 (acidic)
• 7 neutral
• 3.5 (acidic)

34
G. How does a low pH effect freshwater fish?

• Water that is too acidic can impair fish egg
  development and reduce the number of offspring
• Also, low pH causes leaching of metal ions into
  the water which can make the water toxic to the
  fish.

35
H. How does a high pH effect freshwater fish?

• A high pH (above 9) makes the water better able
  to dissolve organic materials such as skin and
  scales
• This will kill the fish.

36
Section C.10 Inappropriate molecular substance
concentration?

• A. Define these terms
• Molecular substance
• Electronegativity -

37
B. How are molecules different than ionic
compounds?

• Molecules have covalent bonds and are made of
  nonmetals. ( No ions!)
• Molecules can be a solid, liquid or gas at room
  temperature.
• Ionic cmpds. Are made of a metal and nonmetal.
  Are made of ions.
• Ionic cmpds. Are solids at room temperature

38
C. What determines if a molecule is a solid,
liquid or gas at room temp?

• The strength of attraction between molecules of
  the same type.
• Not much attraction results in a gas
• Strong attraction results in a solid

39
D. What determines the solubility of a molecular
substance?

• This is determined by which force is stronger,
  the force between the molecules of the substance
  or the force between the molecules and water.

40
E. What part of a water molecule is more
electronegative? Explain.

• The oxygen attracts the electrons more so it is
  more electronegative.
• This creates a (-) charge at the O end and a ()
  charge near
• the H ends.

41
F. Explain what Like dissolves likes means.

• Polar substances dissolve in polar solvents
• Nonpolar dissolve in nonpolar solvent.
• Polar and nonpolar dont mix!!
• Oil water

42
Section C.12 Inappropriate dissolved Oxygen
levels?

• How does the solubility of a gas change as
  temperature changes?
• Gases become less soluble at warmer temperatures.
• Gases are not as soluble as ionic solids.
• Solubility depends on temperature and the nature
  of the gas and the gas pressure.

43
How does pressure affect the solubility of a gas?

• The greater the pressure on the solution the more
  soluble the gas is.
• What does it mean when a glass of pop goes
  flat?
• The CO2 is now at its new solubility at that
  temperature and pressure.

44
C.13 Temperature, Dissolved Oxygen and Life

• Different types of aquatic life have different
  needs in terms of DO (dissolved oxygen)
• In general, most fish need at least 4 ppm.
• Warmer water has lower levels of DO.
• Warmer water increases the fish demand for oxygen
  as well.
• Water that is too hot for too long will suffocate
  fish.

45
What are some causes of drastic changes in water
temperature?

• Industries that put warm water into a river.
• Power plants put warm water back.
• This decreases the DO levels in those areas.

46
Is too much oxygen a problem?

• Yes, it can be if it gets above 110 (is
  supersaturated)
• Can cause gas-bubble trauma in the fish.
• Gas bubbles form in the blood and tissues of the
  fish. The N bubbles block capillaries and will
  kill the fish.
• This can happen at the base of a dam.