Transcript Teacher Quality Grant - Panhandle Area Educational Consortium

Biology Partnership
(A Teacher Quality Grant)
Chemistry II:
Properties of Water and pH
Nancy Dow
Kathrine Alexander
Gulf Coast State College
Panhandle Area Educational Consortium
5230 West Highway 98
753 West Boulevard
Panama City, Florida 32401
Chipley, Florida 32428
850-769-1551
877-873-7232
www.gulfcoast.edu
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Pre-test
Breaks
Q & A boards
Asking questions
Our approach to the
standards & to this lesson
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Florida Next Generation Sunshine
State Standards
• SC.912.L.18.12 Discuss the special properties
of water that contribute to Earth’s suitability as
an environment for life; cohesive behavior,
ability to moderate temperature, expansion upon
freezing, and versatility as a solvent. (Moderate)
Benchmark Clarifications
–
–
Students will explain the properties of water at a conceptual level.
Students will explain how the properties make water essential for life on Earth.
Content Limits
 Items referring to the properties of water are limited to hydrogen bonding, polarity,
cohesive behavior, ability to moderate temperature, expansion upon freezing, and versatility
as a solvent.
 Items may address adhesion but will not assess adhesion
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Bell ringer
Time Warp water droplets
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5
THE PROPERTIES OF WATER :
Water has some very unique properties that make this
molecule unlike ANY other. And we are made up of about
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70% water!
Your body is made up of mostly of water.
Approximately 85% of your brain, 80% of
your blood and 70% of your muscle is water.
Every cell in your body needs water to live.
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Unique properties of Water
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Cover page
• Write the book title - PROPERTIES OF
WATER
• Sketch and color a water molecule
• In the Upper right corner, write your name
PAGE ONE (front side)
• Write the Page title, POLARITY, centered at the top of the
page.
• Draw and color (Oxygen-RED and Hydrogen- BLUE)
water molecules held together by hydrogen bonds
• Write, bullet, and answer these
questions:
– What is meant by polarity?
– Which end of the water molecule attracts most of the electrons
and acts negative?
– Which end acts positive?
– How do water molecules act like “little magnets”?
Water is a ‘Polar Covalent’ molecule(charges at opposite sides of molecule)
‘POLAR’ means an unequal distribution of the
charge.
H2O
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HYDROGEN BOND BETWEEN WATER MOLECULES
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A Drop in the Ocean Lab
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• We’ve heard that wax or oils repel water. But that isn’t
true. Water is so attracted to other water molecules that
anything between them is squeezed out of the way.
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States of Water
• Only substance to that exists free in nature in all
three states
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PROPERTIES OF WATER
• WATER IS THE ‘UNIVERSAL SOLVENT’---It dissolves other “polar”
molecules– a molecule that can attract a water molecule. “Like dissolves like”
“polar dissolves polar”
• WATER MOLECULES ARE COHESIVE AND ADHESIVE---Transport
of water in organisms – example: Trees
– Cohesion- a property of like molecules sticking together (water attracted to
other water molecules”
– Adhesion- the tendency of dissimilar particles to cling to one another
• WATER HAS A HIGH SURFACE TENSION----Water bugs walk on the
surface of water
• FROZEN WATER (ICE) IS LESS DENSE THAN LIQUID WATER SO
IT FLOATS---Keeps organisms alive in the bottom of a frozen lake
• WATER HAS THE ABILTIY TO MODERATE TEMPERATURE– water
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temperature effects coastal communities temperature
PAGE ONE (Backside)
• Write the Page title, UNIVERSAL SOLVENT, centered at
the top of the page.
• Draw and color a solution
including solvent and a solute
solution
• Write, bullet, and answer these questions:
–
–
–
–
–
What is a solvent?
Why is water called a universal solvent?
What is a solute?
Which type of molecules, polar or nonpolar, dissolves in water?
Are materials that dissolve in water hydrophobic or hydrophilic?
Universal Solvent
Since unlike charges attract, the negative end of water will be attracted to the
positive sodium ion. The positive end of water will be attracted to the negative
chloride ion.
Since water is always in motion, it will pull on the ionic compound and move the
ions away from each other. This dissolves the ionic compound.
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Many compounds dissolve in water.
• A solution is formed when one substance
dissolves in another.
– A solution is a homogeneous
mixture.
– Solvents dissolve other
substances.
– Solutes dissolve in a solvent.
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• “Like dissolves like.”
– Polar solvents dissolve polar solutes.
– Nonpolar solvents dissolve nonpolar solutes.
– Polar substances and
nonpolar substances generally remain separate.
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Common Misconceptions
• Students often thinks that all solutes are solids
and all solvent as are liquids.
• Correcting the misconception
– Solutions can involve different states of matter
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PAGE TWO (Front side)
• Write the Page title, COHESION, centered at the top
of the page.
• Sketch and color the water droplet
• Write, bullet, and answer these questions:
– What is cohesion?
– Cohesion produces _____________ tension as the water
molecules hold tightly together.
– How do living things like insects use surface tension?
PAGE TWO (Backside)
• Write the Page title, ADHESION, centered at the top
of the page.
• Sketch and color the picture below.
• Adhesion pulls the liquid up the sides of the straw
(capillarity).
• Write, bullet, and answer these questions:
– Define adhesion.
– Adhesion produces an effect called ______________
action when you place a straw in a liquid
– Explain how adhesion and cohesion help plants move
materials.
• Hydrogen bonds are responsible for three
important properties of water.
 Cohesion - water
molecules “stick” to each other
 Adhesion - water
molecules “stick” to other
substances
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Cohesion
• Water’s tendency
to cling together
• Water in space
When the negative end of a water molecule attracts the
positive end of another water molecule, and the molecules
stick together, this is called cohesion.
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How water stacks up
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Adhesion
• Adhesion, or capillary action, is when water
molecules are attracted to other substances
with a negative or positive charges. This is
why water "climbs" up a piece of paper or a
straw above the surface level of the water.
This figure shows water adhesion
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WATER: STRONG COHESIVENESS
300 ft.
6-ft.-tall
man
Water
molecule
released
into the
atmosphere
Water
molecules
pulled
upward
Water
molecule
pulled into
root system
Because of the
cohesive properties of
water, trees such as the
giant sequoia are able
to transport water
molecules from the
soil to their leaves 300
ft. above.
As each water molecule
evaporates, it pulls
additional water up
through the tree
because of the “stickyness” of the hydrogen
bonds that link the
water molecules.
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Phloem and Xylem
-Phloem-Transport sugars and molecules created by the plant.
Transports food made during photosynthesis.
Xylem-System of tubes in a plant that transport water and dissolved
minerals. The xylem distributes the water throughout the plant.30
Surface Tension
• The cohesive forces between liquid molecules are
responsible for the phenomenon known as surface
tension.
• The molecules at the surface do not have other like
molecules on all sides of them and consequently
they cohere more strongly to those directly
associated with them on the surface.
• This forms a surface "film" that allows insects to
walk on water
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WATER: HIGH SURFACE TENSION
Pressure applied to water surface
Hydrogen
bond
“V”-shaped water molecules are held
together by hydrogen bonds. The bonds
are just strong enough to give water a
surface tension with net-like properties.
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Trouble on the Surface Lab
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LAST PAGE (Inside of back cover)
• Write the Page title, INSULATION, centered
at the top of the page.
• Sketch and color the ice crystal.
• Write, bullet, and answer these questions:
– When is water the densest?
– Explain why ice floats?
– How is a lake or river that freezes over helpful to
the organisms in the water?
WATER: LOWER DENSITY WHEN FROZEN
Water is densest at 4°C
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Expansion of water contributes to the fitness
of the environment for life:
• Prevents deep bodies of water from freezing
solid from the bottom up.
• Since ice is less dense, it forms on the surface
first. As water freezes it releases heat to the
water below and insulates it.
• Makes the transitions between seasons less
abrupt. As water freezes, hydrogen bonds
form releasing heat. As ice melts, hydrogen
bonds break absorbing heat.
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Thermal Expansion
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WATER: HIGH HEAT CAPACITY
1 Heat (energy) from the
sun disrupts some of the
hydrogen bonds between
water molecules.
2 New hydrogen bonds are
formed almost as quickly as
they are disrupted.
Disrupted bond
Newly formed bond
3 Because heat energy
from the sun is used up
breaking and re-forming
hydrogen bonds, the water
temperature doesn’t
increase by much.
4 Molecules that make up
sand, on the other hand,
don’t have so many
hydrogen bonds, so the
heat of the sun just
increases the temperature.
Sun

Sixty percent of your body is water. This helps
you to maintain a relatively constant body
temperature.
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Other unique properties of water
 High boiling point - 100 oC
 Low freezing point- 0 oC
 Viscosity increases as its temperature is lowered
 A relatively high density to support animals with no
or delicate skeletal systems
 Latent heat of evaporation – highest of all substances
 Latent heat of fusion- highest except ammonia
 Transparency – relatively great
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Why is water so important to
living organisms?
• Water acts as a solvent to provide a liquid
environment for biochemical reactions.
• Water is also a transporter of nutrients, waste products, blood, and
materials within cell
• Water dissolves polar compounds and does not dissolve nonpolar
compounds. This is important for both biochemical reactions and crucial
hydrophilic/hydrophobic interactions in protein folding.
• Water is an important reactant in certain biochemical reactions such as
electrolysis reactions and the first step of the photosynthetic electron
transport chain.
• Water has a high specific heat capacity to facilitate better maintenance of
internal temperature and the usage of evaporation to cool down.
Follow up
• Q/A Board
• Problem solving issues in class
• Additional activities
• Properties of Water Lab H.O.T.
• Water Tutorial
• Wonder of Water 6.5 Cloze
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Florida Next Generation Sunshine
State Standards
SC.912.P.8.11 Relate acidity and basicity to
hydronium ion and hydroxyl concentration and pH.
• No specific Biology standard for pH but need to
understand because it is referred to in the enzymes
standard as well as in reference to aquatic systems
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Bell Ringer
• Acid Bases and pH- flipped classroom
• Acid and base rap
• Acid and base Music video
Acids and bases
•
The pH is a measure of how acidic or basic a solution is.
• A scale with values ranging from below 0 to above 14 is
used to measure pH.
More acidic
Neutral
More basic
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Acids and bases
• Substances with a pH below 7 are acidic. An acid is any
substance that forms hydrogen ions (H+) in water.
stomach acid pH between 1 and 3
more acidic
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• A neutral solution has a pH of 7.
pure water pH 7
Acids and bases
• Substances with a pH above 7 are basic.
• A base is any substance that forms hydroxide
ions (OH-) in water.
bile pH between 8 and 9
more basic
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• It is a logarithmic scale, based on powers
of 10, so that 1 pH unit change equals a 10
fold change in H+ ion concentration! A pH
of 6 is ten times more acidic than a pH of
7.
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pH scale is logarithmic – using powers of ten
THE pH SCALE
H+ ion
ACIDS
0
1
2
Battery acid
3
4
5
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Bases are fluids that have a greater proportion
of OH– ions to H+ ions.
• OH– ions bind with H+ ions, neutralizing acids.
• Strong bases are caustic to your skin.
• Bases can be found in many household cleaners.
• Bases are generally bitter in taste and soapy.
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Water
Beer
Soda
OH– ion
BASES
Acids are fluids that have a greater
proportion of H+ ions to OH– ions.
• H+ ions are very reactive.
• Strong acids are corrosive to metals.
• Acids break down food in your digestive
tract.
• Acids are generally sour in taste.
Free
H+
Water
9
10
Baking soda
Coffee
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12
13
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Bleach
Ammonia
Blood

Soda, with a pH of about 3.0, is
100,000 times more acidic than a
glass of water, with a pH of 8.0!49
Free
OH-
pH SCALE
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ACIDS AND BASES
Acids=Free Hydrogens
Bases=Free Hydroxides
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pH value
times acidity or alkalinity exceeds that of pure water (7.0)
Acidic 0
10,000,000
1
1,000,000
2
100,000
3
10,000
4
1,000
5
100
6
10
Neutral 7
1
8
10
9
100
10
1,000
11
10,000
12
100,000
13
1,000,000
Alkaline 14
10,000,000
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How does pH affect life?
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How does pH affect enzymes?
• A change in pH disrupts an enzyme's shape
and structure.
• In general enzyme have a pH optimum.
However the optimum is not the same
for each enzyme.
• Different enzymes might have very
different pH optima
•Green- enzyme pepsin which degrades
proteins (protease) in the stomach
•Red- enzyme carbonic anhydrase that works in
the neutral pH of your cytosol.
Buffers: A Mechanism to prevent pH changes—to keep the pH within
normal limits because they take up excess hydrogen ions (Examples:
Tums or Rolaids are buffers for stomach acidity).--- Our body has buffer
systems (Homeostatic mechanisms)---Example: Buffers to keep our blood
pH at 7.3 - 7.4
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Acid Base Lab
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Cabbage juice indicator
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Follow up
• Q/A Board
• Problem solving issues in class
• Additional activities
• pH Factor -interactive
• Interactive pH scale
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Post Test
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