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A Look at Water and Its Contaminants

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Title: A Look at Water and Its Contaminants


1
A Look at Water and Its Contaminants
2
Chemistry Concepts Covered
  • Physical Properties
  • Diff between evaporation and BP
  • Important Physical Properties of water
  • Density

3
Chemistry Concepts Covered
  • Chemical Properties
  • Types of Mixtures
  • Chemical Formulas/Symbols
  • Electrical Nature of Matter
  • Ions
  • How to Write Ionic compounds

4
Physical Properties of Water
  • 1. What are physical properties of water or any
    other substances?
  • those characteristics shared by all samples of a
    substance w/o changing the substance

5
Physical Properties of Water
  • 2. What is the rarest and most unusual substance
    in the universe? Why?
  • water, very little water has been found in the
    planets of the solar system
  • water has very unusual properties for chemicals
    of its size and composition

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Physical Properties of Water
  • 3. How much of the earths surface is covered by
    water?
  • 70-water is the most common liquid on earth
  • 4. Is water ever entirely pure?
  • No surface water has dissolved minerals in them,
    even distilled water has dissolved gases in them

9
Examples of Physical Properties
  • Color

10
Examples of Physical Properties
  • Is it a gas, liquid, or solid?

11
Examples of Physical Properties
  • taste
  • odor
  • length
  • volume
  • density

12
Physical Properties of Water
  • 5. What are the physical characteristics of
    water?
  • colorless, odorless, tasteless
  • 6. But wait, some water have a definite taste,
    what about that, huh?
  • it is the dissolved stuff in water that can give
    it taste, odor, or even color

13
Physical Properties of Water
  • 8. What is density?
  • How much stuff or mass is crammed in a particular
    amount or volume of matter
  • Mass per volume or Mass / volume or g / mL
  • 9. Give some examples of substances and their
    densities.

14
Density other examples
  • Substance Density(g/cc)
  • Oxygen gas .001331
  • Water 1.00
  • Ice .92
  • ethanol .79
  • Aluminum 2.70
  • Iron 7.87
  • Copper 8.96

15
Density
  • Two materials styrofoam and brick. Same
    volume. Same mass?

16
Density
  • On the microscopic level you can clearly see that
    the brick is more closely bunched together.
    There is more brick atoms per volume than
    styrofoam. We say brick is more dense than
    styrofoam.

17
Density
  • Density is defined as the mass of a substance per
    the volume of the substance
  • Mathematical formula D M/V where D Density,
    MMass(g), VVolume(mL or L)

18
Density
  • Ex. 1 A piece of lead has a mass of 22.7 g. It
    occupies a volume of 2.00 cc. What is the
    density of the lead?

19
Density
  • Ex.2 A piece of lead occupies a volume of 4.00
    cc. What is the mass of the lead?

20
Density
  • 3. A piece of lead has a mass of 302 g. What is
    the volume of the lead?

21
Density
  • Mercury the most dense liquid (13.55 g/cc)

Gold the most dense solid (19.32 g/cc)
22
Physical Properties of Water
  • 10. Rank the phases of matter in terms of most
    dense to least dense
  • most solids--gt most liquid--gt gas
  • 11. What is a good example of an exception to
    number 10?
  • water

23
Physical Properties of Water
  • 12. Why is it so important that water is more
    dense than ice?
  • lakes and ponds freeze at the surface and not at
    the bottom where it would disrupt the food cycle

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Ice is less dense than water
26
Physical Properties of Water
  • 13. How does the Density of water cause erosion
    in nature?
  • rainwater seeps into cracks then expanding as it
    freezes cracking the rock or road even further

27
Physical Properties of Water
  • 14. Why is the boiling point and freezing point
    of water important to the way we measure
    temperature in Science?
  • the Celsius scale is attuned to it, water freezes
    at 0 and boils at 100C

28
Physical Properties of Water
  • 15. What is the difference between boiling and
    evaporation?
  • in both, liquid is turning to gas
  • evaporation occurs at any temperature even 0C,
    boiling takes place only at around 100C
  • evaporation only occurs at the surface, boiling
    takes place under the surface

29
Physical Properties of Water
  • 16. Can we see steam?
  • No, you cannot see steam, you can only see water
    vapor when millions of water gas have stuck
    together to form a tiny droplet, like in clouds

30
Physical Properties of Water
  • 17. What is it about the BP of water that is
    important to life?
  • water has an unusually high BP allowing water to
    exist over a large temperature range
  • we are made of mostly water

31
Physical Properties of Water
  • 18. What is another important physical property
    of water critical to plants?
  • high surface tension-water sticks to itself very
    strongly
  • plants make use of this in order to allow them to
    draw water from their roots to their leaves

32
II. Mixtures and Solutions
  • 19. What is a mixture?
  • two or more substances that are combined but each
    retain their own properties
  • 20. What is a heterogeneous mixture?
  • mixture that is not completely uniform
    throughout, has layers
  • salt and pepper muddy water oil and water

33
II. Mixtures and Solutions
  • 21. What is a homogeneous mixture?
  • mixture that has the same consistency or uniform
    throughout
  • salt water air drinking water
  • 22. What is another name for a homogeneous
    mixture?
  • solution

34
II. Mixtures and Solutions
  • 23. What are the two parts of a solution called
    and what are they?
  • solute-the stuff that gets dissolved or
    dispersed(salt in salt water)
  • solvent-the stuff that does the dissolving or
    dispersing(water in salt water)

35
II. Mixtures and Solutions
  • 24. Water mixtures are classified according to
    the size of the particles dispersed in the water.
    What are the three classes called and what
    distinguishes one from the others?
  • Suspension-very large, easily seen particles.
    will disperse when mixed but eventually settle
    out (ex. muddy water)

36
II. Mixtures and Solutions
  • Colloid-very tiny particles that cannot be seen
    that make water look cloudy ex. Milk
  • Solution-particles are so small and so evenly
    distributed that they appear to be clear ex.
    salt water drinking water

37
Whole milk 1000x
38
Whole milk 400x
39
Non Fat milk 400x
40
II. Mixtures and Solutions
  • 25. How can you tell colloid from a solution?
  • Called the Tyndall Effect

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44
Molecular View of Water
  • 26. What is water made up of?
  • atoms of 2 different elements-Oxygen and Hydrogen

45
Molecular View of Water
  • 27. What is the difference between an element
    and a compound?
  • elements are made up of the same type of atom
    (Copper Iron Oxygen gas)
  • compounds are made up of two or more different
    atoms(carbon dioxide CO2 water H2O drinking
    alcohol C5H7OH, ammonia NH3, Table salt, NaCl)

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47
Molecular View of Water
  • 28. About how many elements are found in nature?
  • 90
  • 29. About how many compounds are there?
  • over 8 million
  • 30. What holds atoms in a compound together?
  • chemical bonds

48
Molecular View of Water
  • 31. What do we call the smallest unit of a type
    of compound?
  • a molecule

49
Molecular View of Water
  • 32. What are chemical reactions?
  • involves the breaking and forming of chemical
    bonds causing atoms to become rearranged into new
    compounds, usually the new things that form have
    radically different properties from the compounds
    that formed it

50
Molecular View of Water
  • 33. What are chemical properties?
  • the properties of a substance that describe how
    it reacts with other substances
  • oxygen reacts with iron to form rust
  • hydrogen and oxygen gas will react explosively to
    form water
  • sodium metal and chlorine gas will react with
    great heat to form table salt

51
Examples of Chemical Properties
  • How a chemical reacts with another chemical is a
    chemical property

52
Examples of Chemical Properties
How a chemical reacts with another chemical is a
chemical property
53
Examples of Chemical Properties
  • Reaction with water to produce new substances

54
Examples of Chemical Properties
  • How a substance reacts in the presence of heat

55
Chemical vs Physical Changes
  • all reactions in chemistry are either physical or
    chemical changes
  • by understanding what kind of change occurred we
    can better understand the reaction

56
Chemical vs Physical Changes
  • Physical changes involved a change in odor, size,
    color, phase but not a change in what the
    substance is.
  • Chemical changes always results in the
    production of a new substance. What the
    substance once was, it no longer is...

57
Chemical Changes
  • Chemical changes always results in the production
    of a new material

58
Chemical v Physical Changes?
  • Clearly the components do not react with one
    another they are dispersed one in another and can
    be easily separated Physical Change

59
Chemical v Physical Changes?
  • Production of new materials Chemical Change!

60
Chemical v Physical Changes?
  • What is produced now has a new mass therefore it
    has added something from the air to its chemical
    makeup. A new substance Chemical

61
Symbols and Formulas
  • 34. What are chemical symbols?
  • letter used to represent the elements
  • C Carbon H Hydrogen NaSodium

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63
Symbols and Formulas
  • 35. What are chemical formulas?
  • if symbols are the letters of the chemistry
    alphabet, chemical formulas are the words
  • formulas tells us two things
  • 1. the elements involved in the compound
  • 2. how many atoms of each element are in the
    compound using a subscript

64
Examples
  • CO carbon monoxide
  • C12H22O11 sugar
  • CaCl2 Deicing salt
  • KNO3 gunpowder

65
Symbols and Formulas
  • 36. What are chemical equations?
  • the chemical sentences
  • they describe what things are reacting and what
    they are becoming
  • chemical formulas are used
  • 2H2 O2 --gt 2H2O

66
Symbols and Formulas
  • 37. What do we call what is used up in a
    reaction?
  • reactants
  • 38. What do we call what is produced in a
    reaction?
  • products

67
Symbols and Formulas
  • 39. What is the molecular structure?
  • it describes not only what a compound is made of
    but what it looks like as well

68
Water
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  • 40. What are the diatomic molecules?
  • Elements that exist in nature as couplets, never
    as single atoms
  • There are 7 of them
  • Just remember Br HONClIF

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75
Electrical Nature of Matter
  • 41. What are some examples of the electrical
    nature of matter?
  • static cling shocking yourself on a door knob
  • 42. Summarize the electrical properties
  • positive particles(protons) are attracted to
    negative particles(electrons)
  • positive particles repel each other
  • negative particles repel each other

76
Electrical Nature of Matter
  • 43. How do these properties help explain
    bonding?
  • bonding occurs when the electrons of one atom
    becomes attracted to the protons of another and
    they get stuck together, this glue is called a
    chemical bond
  • 44. Are all atoms equally attractive to the
    electrons of other atoms?
  • No some are more attractive than others

77
Electrical Nature of Matter
  • 45. What are polar molecules?
  • molecules that have an uneven distribution of
    electron due to
  • 1. unequal sharing of electrons because one atom
    is slightly more attractive than the other
  • 2. the shape

78
Electrical Nature of Matter
  • 46. How is it that water is known as a polar
    molecule?
  • Oxygen is very attractive, it will attract the
    electrons of hydrogen to it. Because it does
    this it is kind of negative. The Hydrogen part
    is very positive because it has very little
    control over its electrons.

79
Electrical Nature of Matter
  • 47. How do these properties affect water?
  • it gives water ability to stick to each other
    really strongly
  • water becomes like a little magnet
  • 48. What happens when one really ugly atom and
    one really pretty atom come in contact with each
    other?
  • the outer electron of the ugly atom will take off
    and be absorbed the pretty one

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Electrical Nature of Matter
  • 49. What are ions?
  • what atoms are called when they lose or gain
    electrons
  • 50. What are the two types of ions?
  • positive ions or cation-the atoms that loses the
    negative electron
  • negative ions or anion-the atom that gains an
    extra electron

82
Electrical Nature of Matter
  • 51. What are the ions that make up NaCl?
  • one Na ion and one Cl- ion

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  • 52. What does it mean to be a 1 ion? Give an
    example.
  • You have lost 1 e- so you have one more positive
    than negative
  • 53. What does it mean to be a -1 ion? Give an
    example.
  • You have gained 1 e- so you have more negative
    than positive

87
  • 54. What does it mean to be a 2 ion? Give an
    example. What does it mean to be a -2 ion? Give
    an example.
  • You have lost 2 e- so now you have 2 more
    positives than negatives.
  • You have gained 2 e- so now you have 2 more
    negatives than positives

88
  • 55. What is the most important rule to remember
    when dealing with ions?
  • You do not gain protons(positives) you only gain
    e-(negatives)

89
Ions and Ionic Compounds
  • 56. How are ionic compounds named?
  • the first name comes from the positive ion
  • the second name is the altered name of the
    negative ion -ide is added as the new ending
  • 57. What is the name for the following
  • a. NaCl b. MgCl2
  • c. LiS d. Al2O3

90
Ions and Ionic Compounds
  • 58. How do you write chemical formulas?
  • 1. Place the positive ion symbol first with
    correct charge(check PT for that)
  • 2. Place the negative ion symbol second with the
    correct charge(check PT for that)
  • 3. If you see a Roman Numeral-that tells you
    what the charge HAS to be, ignore what the PT
    tells you
  • 4. Use criss cross method

91
Lab 2 Water Testing
  • 1. How do chemist know when a certain impurity
    exists in water?
  • They perform confirming test to prove that it is
    there or not
  • 2. What is a typical confirming test?
  • A chemist will add a chemical to water that will
    only react with the impurity and with nothing
    else. It will then form a precipitate

92
  • 3. What is a precipitate?
  • A solid that is formed when a positive and
    negative ion meet for the first time and fall in
    love, usually associated with a color change
  • 4. These tests are called qualitative, why?
  • We are only concerned with figuring out what it
    is not how much we have(quantitative)

93
  • 5. What four ion impurities will we be testing
    ORHS water for?
  • Iron III(Fe3), Calcium(Ca2), Chloride(Cl-), and
    Sulfate(SO4-2)
  • 6. Why is it important to call Iron, Iron III?
  • Iron comes in two forms, Fe2 and Fe3

94
  • 7. You are going to perform the confirming tests
    on four different water samples? Why three?
    Which are they?
  • A. Reference this solution will have the ion
    in question, it helps you to know what to look
    for
  • B. Control Pure water, will not have it
  • C. ORHS water maybe,maybe not
  • D. Creek water

95
  • 8. Would you expect the ion to be present in
    large amounts in the ORHS water?
  • No it should be in small amounts.
  • 9. Should there be a difference between the
    Reference and a positive ORHS test?
  • Yes, the ORHS test should be fainter

96
  • 10. When you perform the test, why should you
    use the toothpick that will be provided?
  • To thoroughly mix the two chemicals
  • 11. Should you use the toothpick on the next
    test?
  • No it would contaminate the next sample, clean
    the toothpick

97
  • 12. You will be using a 24 well plate, what is
    it?
  • A plastic tray for holding small amounts of
    chemicals, take a look

98
  • 13. Since we will be using these trays and the
    color change may be faint, how can we make it
    easier to see the color change?
  • Hold a white sheet paper under the plate
  • Use the table top if you expecting to see a white
    precipitate

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Ions and Ionic Compounds
  • 59. Write the chemical formulas for the
    following
  • a. Barium oxide b. Potassium fluoride
  • c. Aluminum oxide d. Strontium chloride
  • 60. What are Polyatomic Ions?
  • groups of atoms that together form an ion

101
Ions and Ionic Compounds
  • 61. How do you write chemical formulas with
    polyatomic ions?
  • the same as regular formulas except that you
    place parenthesis around the entire polyatomic
    ion when you have more than one of them
  • 62. Where do you find polyatomic ions and their
    charges?
  • on your ChemOut

102
Ions and Ionic Compounds
  • 63. Write the chemical formulas for the
    following
  • a. Barium sulfate b. Magnesium hydroxide
  • c. Aluminum sulfite d. Sodium peroxide
  • 64. How do you write chemical names involving
    polyatomic ions?
  • DO NOT CHANGE THE NAME TO -IDE ending, just
    write the PI name as is

103
Dissolving Ionic Compounds
  • 65. What is a good way of picturing what
    dissolving is like?
  • like a tug of war
  • 66. What causes an ionic solid substance to
    dissolve?
  • if the forces that attract the ions to water is
    stronger than the force that attracts the ions to
    each other

104
Dissolving Ionic Compounds
  • 67. Why is water an exceptional dissolver of
    ionic solids?
  • water is a VERY polar substance, its oxygen part
    is very negative while its hydrogen parts are
    very positive
  • 68. Illustrate how water dissolves NaCl

105
  1. Sodium chromate
  2. Copper II hydroxide
  3. Iron III chloride
  4. Barium phosphite
  5. FeCl3
  6. NaOH
  7. Sr(NO3)2
  8. CuF2

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Pure and Impure Water
  • 69. Does any community in the world receive pure
    water from their treatment plant?
  • No
  • 70. Why is it useless to insist on pure water?
  • the cost of purifying would be too high
  • it would still be impossible because as long as
    it is in contact with the atmosphere, gases such
    as oxygen, nitrogen, and carbon dioxide will
    dissolve in it

108
Pure and Impure Water
  • 71. Why would it be best to not purify water?
  • some gases and minerals give water a pleasing
    taste
  • some dissolved substances are good for humans
  • small amounts of chlorine containing compounds
    kills bacteria

109
Pure and Impure Water
  • 72. What are some harmful substances that can be
    found in water and what do they do?
  • High concentrations of
  • Iron bad taste and deposits on pipes and
    fixtures
  • Sulfur bad odor
  • Mercury(Hg), Lead(Pb), Cadmium(Cd) and
    Arsenic(As) can dissolve and be deadly even in
    low concentrations

110
Pure and Impure Water
  • 73. What are some other sources of harmful water
    contaminants?
  • pesticides and commercial and industrial waste
    products

111
b
  • One of the most important jobs of a scientists is
    knowing what questions to ask
  • It helps focus your thinking
  • Large problems can be focused into smaller
    problems that can be solved
  • To solve the mystery, we need to eliminate some
    possibilities and zero in on promising ones

112
  • Scientists try to disprove all but one of the
    possibilities in order to conclude what is the
    answer
  • Remember that there had been a similar fish kill
    in the Snake River, its cause was water related
  • Next Chapter, we will look a several kinds of
    water soluble substances and how they could have
    affected the fish
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