Transcript Bonding - Schoolwires

Water Bonding
Water has unusual properties
Polar Covalent Bonding of Water:
Unequal sharing of electrons
(intramolecular forces)
OR
H
O
Means partially +
Means partially -
H
Hydrogen Bonds
hydrogen bond = is the
attractive force between
the hydrogen attached to
an electronegative atom
(tendency to attract
electrons) of another
molecule (usually O, N, F)
Hydrogen Bonding Dance (1 min)
• Youtube Polarity and Hydrogen Bonding
• (3:52)
Water Molecules
• Can bond to four other water molecules
• H+ end attracts the O-ends
Polarity of Water helps
H-bonds form
• Uneven sharing of electrons
• Between slightly (+) H atom to a
slightly (-) atom of a different
molecule
• H-bonding of water
• H- Bonding and polarity
Hydrogen Bonds between Water
Molecules
• Weaker than covalent and ionic
bonds
• Stronger than van der Waals
Cohesion
• Water is attracted
to other water
molecules
(similar polar
molecules)
• H-bonding
between water
molecules hold
them together
Like in
drops
Cohesion is why a waterfall, a
stream, a water drop forms
Adhesion
• Attraction of unlike
substances
• EX: water to the
sides of a glass
tube
• Drop to leaf
Strong
adhesion
to glass
Not so
much with
plastic
Adhesion or Cohesion?
Surface Tension
-the attraction of molecules
to each other (cohesion) on
a liquid's surface pull
inward (due to H-bonds) to
create a “film”
A screen showing surface
tension youtube
Water molecules
pull in all
direction not on
the surface
Surface tension
is responsible
for the shape of
water droplets
Surface Tension
allows a Penny
or Paper Clip to float
?Surface Tension and Capillary
Action?? - YouTube
H-bonds pull in
water to create
a “film”
Water Strider
• Jesus Christ Lizard (natl geo)
(1.25 mins)
• Can stand on
top of water
• Water Strider on Pond
Surface (44 secs)
See indentations of water
strider’s feet in water.
High Specific Heat
• = the amount of heat per
unit mass required to
raise the temperature by
one degree Celsius.
• The specific heat
of water is higher
than any other
common
substance. WHY?
• Have to break/form
those H-bonds.
Phases of Water
• Describe how the molecules change
(speed and spacing between
molecules) as the temperature
changes.
• Water Phase Change Animation (keep
clicking on the “increase heat”)
• Did the water molecules break apart or
did just the spacing between them
change?
Note the spacing between the
water molecules
Heat of fusion = needed to melt ice
(solid to liquid)
Heat of vaporization = needed to
evaporate to water vapor (liquid to gas)
• (note how long it takes to break the Hbonds)
Water has High Heat of
Vaporization
• Takes a high
temperature to
evaporate, or boil
water
• Need to break those
H-bonds
Water has High Heat of Fusion
(Amount of heat to go from solid to
liquid)
• Takes a low
temperature to freeze
water (loses at lot of
heat)
• Those H-bonds must
form
Look at the spacing and speed of
molecules in each phase
• Vision Learning (scroll down to Liquid Water
and H-bonding and to Ice and H-bonding)
What’s the difference between…
• Heat
• Temperature
• Total amount of
energy of the
atoms/molecules
• A number of
the average
speed of
molecules
Which has more heat…10 mL of 50o C water
or 100 mL of 50oC water?
•
• Going from water
vapor to liquid to solid
ice
• As heat is released the •
attraction between the
molecules
(intermolecular forces)
increases
SOLID ICE
Going from ice to
liquid water to water
vapor
As heat is taken in the
attraction between the
molecules
(intermolecular
forces) decreases
LIQUID WATER
WATER VAPOR
Evaporative Cooling
• The water of the surface of the skin
absorbs heat to change water from liquid
to gas. You feel cooler.
Water has High Specific Heat
• Takes a lot of heat to raise the
temperature of water 1oC(break the
H-bonds)
• This is why coastal areas have milder
climates.
Kelley’s Island
• Has the same weather as northern Ohio
except…
• “The still warm lake keeps us warmer in
the fall, but the still cool lake gives us cold
breezes in the spring.”
Water expands upon freezing
• If water worked like
other liquids, then
there would be no
such thing as an ice
berg, the ice cubes
in your soft drink
would sink to the
bottom of the glass,
and ponds would
freeze from the
bottom up!
Ice forms an Open lattice
• Below 4oC (H-bonds form)
• Ice floats
• H-bonds are
H-bonds
more stable
in the solid
form of water
Ice Expands and is Less Dense
than Liquid Water
4 oC
Liquid
Solid
Water is the “Universal Solvent”
• Means it can
dissolve a lot of
substances due to
its polarity
• Dissolving NaCl in
water movie
• dissolve animation
Water is the Universal Solvent
• What types of compounds are good
at dissolving?
–Polar
–Ionic
–WHY?
–Opposite charges attract
–Remember: Likes dissolve likes:
Polar into polar/nonpolar into
nonpolar
Aqueous Solution
• Means a solution in which water
is the solvent
• Ag+(aq) + Cl-(aq) → AgCl(s)
• EXAMPLES: blood, Coke, Pepsi, urine,
Tea, coffee
Mixtures-Solutions-Suspensions
• Mixtures: 2 or more elements physically
mixed (NOT CHEMICALLY BONDED)
– A. Solutions: type of mixture with evenly
distributed ions throughout
– B. Suspensions: Mixture of water and
undissolved material keeping the small
materials suspended
Can you identify: MixturesSolutions-Suspensions?
Oil and
Water
Sand and Salt
Groups of Elements
What is the difference?
What’s the difference
between…
• Mixtures, solutions, suspensions,
and
COMPOUNDS?
COMPOUNDS ARE
CHEMICALLY JOINED…the
others are physically mixed.
SOLUTIONS
• When one substance dissolves
another substance.
• SOLVENT + SOLUTE =
SOLUTION
• Solvent=material doing the
dissolving (surrounding the ions)
• Solute=what is being dissolved
Salt Solution
Which is the
solvent?
Which is the
solute?
Water is solvent.
Salt is the solute.
Amphipathic
• Bipolar
• A molecule that is water-loving (polar)
at one end and water-hating (nonpolar, like oils) at the other end
How does detergent work?
Soap has a water-loving
(hydrophilic) and a water-hating
end (hydrophobic).
Soap (hydrophobic end) attaches
to the oil and also to the water
(hydrophilic end) to wash away
the oil. (animation, wait for it)
How Soap Works
Capillary Action
Capillary action – the narrower the
tube the higher the water rises
a. Adhesion - of water to tube
b. Cohesion-water to water (column of
water)
Meniscuswater
creeps up
the sides of
the glass
tube
Note size of tube diameter and
the height the liquid rises
Capillary Action
or Capillarity
• The thinner the straw
or tube the higher up
capillary action will
pull the water.
•
Flowers and Food Coloring
•
Water transport in xylem tubes youtube
•
surface tension and capillary action youtube
Transpiration
• Loss of water vapor from parts of plants,
especially in leaves
• ?Transpiration?? - YouTube
Explain how each of these allow
water to pull up a plant?
• Cohesion
• Adhesion
• Transpiration
?Transpiration?? - YouTube
• Can you explain what is going on in this
video?
• ?Flowers and Food Color Time Lapse?? YouTube
Capillarity in Plants
• Surface Tension and Capillarity You Tube
Video
• Water Transport in Plants
Solutions
• A SOLUTE is the substance to be
dissolved (sugar).
• The SOLVENT is the one doing the
dissolving (water).
What is the difference?
SALT SOLUTION
• Animation of Salt Dissolving in Water
• Dissolve Another Nice Animation
• When water is the solvent, the
solution is called an aqueous
solution.
FYI
• The solvent is defined as the
substance that exists in a greater
quantity than the solute(s) in the
solution.
• Generally polar or ionic compounds
will only dissolve in polar solvents.
Dissociation of Water
(breaks into its ions)
• Acids release H+ (hydronium)
• Bases release OH- (hydroxide)
Color Pencils and Handout
• Animations of Transfer of H+ ions
• Acid Strength Animations (contrast the H+
concentrations of HCl and HF)
ACIDS: release a hydrogen ion (H+) without
releasing a hydroxide ion
• BASES: produce hydroxide ion (OH-)
when they dissociate
ACID: increases H+
BASE: increases OH-
H+ + OH-
H2 O
• Why would water have a neutral pH even
though the water ions dissociate?
• Equal number of H+ and OH-
Hydronium Ion = H+
Hydroxide Ion = OH-
• Animations of Acids and Bases
•
pH
at pH 7.0, a solution is
neutral (H+ = OH-)
• * at lower pH (1-6), a solution
is acidic (H+ > OH-)
• * at higher pH (8-14), a
solution is basic (H+ < OH-)
• *
pH
• = the negative logarithm (base 10) of
the molar concentration of dissolved
hydronium ions (H3O+). SAY WHAT?
• a low pH indicates a high concentration of
hydronium ions (acidic)
• a high pH indicates a low concentration of
H+ ions (basic)
• Bozeman: Acids, Bases, and pH (13:13)
• This negative of the logarithm matches the
number of places behind the decimal
point.
• For example, 0.1 molar hydrochloric acid
should be near pH 1 and 0.0001 molar
HCl should be near pH 4 (the base 10
logarithms of 0.1 and 0.0001 being 10−1,
and 10−4, respectively).
• What would be the pH of 0.0000001 M H+
or 10-7?
• pH7
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
pH
[H+]
[OH-]
[H+] X [OH-]
0
1
2
3
4
5
6
7
8
9
10
11
12
13
1 X 10-0
1 X 10-1
1 X 10-2
1 X 10-3
1 X 10-4
1 X 10-5
1 X 10-6
1 X 10-7
1 X 10-8
1 X 10-9
1 X 10-10
1 X 10-11
1 X 10-12
1 X 10-13
1 X 10-14
1 X 10-13
1 X 10-12
1 X 10-11
1 X 10-10
1 X 10-9
1 X 10-8
1 X 10-7
1 X 10-6
1 X 10-5
1 X 10-4
1 X 10-3
1 X 10-2
1 X 10-1
1 X 10-14
1 X 10-14
1 X 10-14
1 X 10-14
1 X 10-14
1 X 10-14
1 X 10-14
1 X 10-14
1 X 10-14
1 X 10-14
1 X 10-14
1 X 10-14
1 X 10-14
1 X 10-14
• 14
1 X 10-14
1 X 10-0
1X
10-14
acid
neutral
base
pH = -log[H+]
• At equilibrium, the concentration of H+ is
1.00 × 10-7, so we can calculate the pH of
water at equilibrium as:
• pH = -log[H+]
• = -log[1.00 × 10-7]
• So pH = 7.00
pOH = -log[OH-]
• NEUTRAL
• pH+ + pOH- = 14.00 at 25°C
What is H+ when
OH - = 1 x 10 – 9 M?
• pH + pOH = 14.
(pH is the negative log of the
concentration of H+ ions, while pOH- is the
negative log of the concentration of OHions.)
If the concentration of OH- is 10-9 = pH 9
Subtract that from 14 to get the pH =
14 – 9 = pH5
Two Ways to Contrast Acids and
Bases
• acid: generates [H+] in solution
base: generates [OH-] in solution
• acid: anything that donates a [H+] (proton
donor)
base: anything that accepts a [H+] (proton
acceptor)
• Good Activities on pH understanding (The find
the answers areas)
How much more?
• For every pH level lower there are 10
X’s more H+ ions
• So…… pH 2 has how many more H+ ions
than pH 3?
• 10
• So…pH 2 has how many more H+ ions
than pH 4?
• 100
• Quia - The pH Scale
Buffer
• A substance that
resists a change in
pH when small
quantities of acid or
base are added
• (they are in the pH
solutions for the
duckweed)
• When acids or bases are added to pure
water, they immediately produce H3O+ or
OH- ions that decrease or increase the
pH, respectively.
• Buffer systems resist large pH changes
because added acids or bases are
neutralized by the existing HA/A(acid/base) system (equilibrium).
Where are buffers important?
• Keeping pH in the blood constant (normal
blood pH is 7.4)
Homeostasis: regulation of the internal
environment and to maintain a stable,
constant condition
• The body is very
sensitive to its pH
level, so strong
mechanisms
exist to maintain
it.
• Discovery Health
"Homeostasis"
Kidneys regulating homeostasis
• The body needs to have the consistent
and proper amount of water, salt, and acid
in the blood. The kidney keeps these
things constant.
• If there is too much water, the kidney puts
more water in the urine. If there is not
enough water, the kidney puts less water
in the urine.
Where are buffers important?
• Pharmaceuticals
• Industry (cleaners, cosmetics, aquarium)
• Working with enzymes
Get Extended Response
Assignment
• Choose two ways the body maintains
homeostasis.
DUE:______________
WORTH:_________
Homeostasis Analogy
Work in Groups to Fill in Chart
Fishbowl
Water
Glass Bowl
Air Pump
Filters
Heater
Feeder
Human Body Function
Fishbowl Model
of homeostasis
Fishbowl
Human body
Function
Water
Body fluid
Internal environment
Glass bowl
Skin
Barrier (internal vs. external)
Fish
Cells
Stay alive
Air pump
Lungs
Keep O2 level constant (high)
Filter
Kidneys
Keep nitrogen wastes constant (low)
Heater
Muscles
Keep temperature constant (high)
Feeder
Digestive system
Keep nutrient levels contant (high)
Everything working together
Relatively constant conditions
pH Problems
• Acid Precipitation: burning of fossil fuels
(coal, oil, gas) alter pH
• Sulfur and nitrogen dioxides add to water
and make sulfuric acid and nitric acid.
• Map of US area acid precipitation pH
pH Problems
• Ocean acidification = CO2
dissolved in water lowers pH (more acidic)
to make carbonic acid
• CO2 + H2O
H2CO3
• Reduces carbonate ions
to make shells, coral,
and skeletons.
Properties of Water Lab
Overall Review
• Bozeman Properties of Water (10
minutes)