Properties of Water_1_.ppt

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					                p. 46
Properties of
Water Notes
    I. Structure
Ø   2 Hydrogen atoms + 1 Oxygen atom -> H2O


                        +
        +       +           -            -
            -       -
                             -   8+8n
                                        -    +                 +
                                             --           --
    2 Hydrogen atoms        --          --
                                             -    8+ 8n
                                                          -
                        1 Oxygen atom        --           --


                                              H 2O
2.polar – has charged areas
  (hydrogen side positive,
  oxygen side negative)




3.Opposite ends attract – water molecules
  try to stick together
II. Properties of Water
Ø       Capillary action – water molecules are
        attracted to each other & surrounding
        materials
        Examples:
    •     Meniscus
    •     Straws
    •     “Wick” away moisture
a)   Cohesion – like molecules stick
     together (ex: raindrops)

b)   Adhesion – unlike molecules stick
     together (ex: raindrops cling to a line)
2. Surface tension
• Tight surface of water
• Caused by polar molecules pulling on
  each other
3. Universal Solvent
• Water dissolves many substances
• Solution – mixture formed when one
  substance dissolves in another
• Solvent – substance that does the
  dissolving
    4. High Specific Heat
• Amount of heat needed to
  increase the temperature of a substance
  by 1oC
• High because water is polar
• Effects:
    •   Water takes longer to heat up or cool down
III. Changing State
Ø    States of Matter:
    a)   Solid – close molecules, rigid structure (ice)
    b)   Liquid – molecules move freely, take shape of
         container (water)
    c)   Gas – molecules move very freely,
         spread out (water vapor)
2.   Evaporation - Change from liquid to gas

                               Gas




3.   Condensation – Change from gas to liquid
4.   Freezing – Change from liquid to solid

                                Solid




5.   Melting – Change from solid to liquid
Comprehension Check
1) A water molecule is made up of

a.two hydrogen atoms bonded to an oxygen
  atom.
b.two hydrogen atoms bonded together.
c.two oxygen atoms bonded to a hydrogen
  atom.
d.two oxygen atoms bonded together.
2) Because water consists of polar
molecules,

a.most of it is found at the North and South
  Poles.
b.water molecules tend to stick together.
c.it falls as sleet or snow when temperatures
  are cold.
d.it can be attracted using a magnet.
3) Tightness across the surface of
water that is caused by polar
molecules pulling on each other is
called

a.surface tension.
b.capillary action.
c.condensation.
d.polar action.
4) Water is often called the universal solvent
because


a.it can cling to the fibers of paper and cloth.
b.it dissolves so many substances.
c.it exists in all three states on Earth.
d.its frozen form floats on its liquid form.
 5) Water is the only substance on
 Earth that

a.commonly exists in all of its different
  states.
b.freezes at very low temperatures.
c.boils at very high temperatures.
d.exists in the liquid state.
   6) The process by which a gas
   changes into a liquid is called

a.evaporation.
b.condensation.
c.melting.
d.freezing.
    Experiment with Water Properties
Ø   Pick a water property to                    Available Materials
    experiment with. Observe your           •    Dropper
    property in action.                     •    Water
Ø   What happens normally?                  •    Penny
Ø   Is there any way to affect what         •    Soap
    happens?                                •    Salt
Ø   Write a paragraph about what            •    Graduated cylinder
    you observed.                           •    Straw
                          Properties        •    Food coloring
                    •   Capillary action    •    Pepper
                    •   Adhesion            •    String
                    •   Cohesion            •    Paper towels
                    •   Surface tension     •    Wax paper
                    •   Universal solvent   •    ?? (Ask if I have it)
Example Experiments with Water Properties

•   Follow that String (p. 49)
•   How many drops of water fit on the side of a
    penny? (p. 51)
•   What effect does soap have on the surface
    tension of water?
•   Can you prevent a meniscus from forming on a
    graduated cylinder?
•   How many coins can you fit into a full glass of
    water?
•   Will a pin float on top of water?
                                         References
Ø   http://learn.sdstate.edu/Deb_Pravecek/Chem106L/Chem106L/estimating_between_graduations.htm
Ø   http://www.madsci.org/posts/archives/feb98/887637827.Ch.r.html
Ø   http://www.southwest.com.au/~jfuller/liquids/hydrometers.htm
Ø   http://www.newton.dep.anl.gov/askasci/chem00/chem00060.htm
Ø   http://www.tappi.org/paperu/fun_science/towelAbsorb.htm
Ø   http://www.pbase.com/minoltaman/image/31683275
Ø   http://www.howard.k12.md.us/res/rm/chris/Raindrop.gif
Ø   http://discover.edventures.com/functions/termlib.php?action=&termid=259&alpha=s&searchString=
    http://discover.edventures.com/functions/termlib.php?action=&termid=259&alpha=s&searchString=
Ø   http://fizyka.phys.put.poznan.pl/~pieransk/Physics%20Around%20Us/Surface%20tension.jpg
Ø   http://discover.edventures.com/images/termlib/s/specific_heat/support.gif
Ø   http://www.conwaycorp.com/water/services/experiments.html

				
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Lingjuan Ma Lingjuan Ma
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