Agenda
 Go
over Labs
 Review
 Water
Quiz: Practice Problems: Draw Models
Notes/PPT
 Bozeman
 Property:
Group
1
Yeast Inquiry Lab Reports

Title- specific to YOUR experiment

Research: in text citations, works cited sheet, paragraph form

Variables: How are they measured?

Independent/dependent variables- approved ahead of time= should not have
had any points off

Control vs. constant variables
 A scientific control is an experiment or observation designed to minimize the
effects of variables other than the single independent variable

Reason: scientific principles

Application: expand detail, cite sources
2
Structure and Properties of
Water
CP Biology
Ms. Albu
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4
Water in Space
Video
http://www.huffingtonpost.com/2013/04/22/washclothspace-iss-astronaut-chris-hadfieldvideo_n_3131531.html?utm_hp_ref=iss
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Structure: Water is a Polar Molecule
 Oxygen:
8 protons
-Pulls shared electrons
closer to oxygen
 Slightly
negative
charged oxygen and
slightly positive
hydrogen
6
Form Hydrogen bonds
hydrogen bond
between (+) and
(-) areas of
different water
molecules
Partial positive
attracted to
partial negative
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Hydrogen Bonds
 Polar
nature of water causes it to be attracted to
itself
 Causes
water to cling to itself and other
substances
 Weak
bond that is easily broken
http://programs.northlandcollege.edu/biology/Biology1111/animation
s/hydrogenbonds.html
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Water’s Properties

Cohesion

Adhesion

Capillarity

High specific heat (temperature moderation)

Solid water (ice) is less dense than liquid

Universal Solvent

Dissociation
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Cohesion
 Water
molecules stick
to each other
 Water
clings to polar
molecules through
hydrogen bonding
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Surface Tension
Cohesion is responsible for surface tension –
molecules on the surface hold onto each other
Water acts like a ‘skin’
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Adhesion
 waters
sticks to
other substances
 water
is adhesive to
any substance that it
can form hydrogen
bonds
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Cohesion
versus Adhesion
Hint: co means
together so cohesion
is water molecules
together
Hint: think
Bandaide adheres
cloth to skin
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Capillary Action
Hint: water through a straw
adhesion,
cohesion and
capillary action
Water molecules move
upward through
narrow tubes against
the force of gravity
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Temperature Moderation
Water heats and cools
slowly. Energy used to
break hydrogen bonds.
 Evaporation
of water from the leaves of
plants or the skin of animals removes
excess heat.
 Helps
maintain homeostasis because
temperature changes in the environment
dont affect temperature of water in the body.
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“Universal” Solvent
 Likes
dissolve likes
 Dissolves
other polar substances like sugars and
proteins
 Dissolves
ionic compounds like salt
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Water clings to polar molecules
causing them to be soluble in
water.
 Hydrophilic
– “water loving”
substance easily combines
with water
 Hydrophobic
– “water
hating”
repelled by water – nonpolar
molecules
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Solid water (ice) is less dense than liquid

Ice is less dense than water: each molecule of ice is hydrogen
bonded to four of its neighbors
Density = mass/volume
same mass
but a larger
volume
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Bodies of water don’t freeze
solid because ice floats
 water expands as it
solidifies
water freezes from the
top down
 organisms can still
live in the water
underneath the ice
during winter
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Dissociation of Water
 Oxygen
atom from one water molecule can remove
hydrogen atom from other water molecule
 H2O

H+ + OH-
 Dissociation
happens when water molecule is broken
apart into two ions of opposite charges
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Dissociation of Water
 H2O

H+
+
Hydrogen ion
OHhydroxide ion
The free H+ ion reacts with another water
H+ + H2O

H3O+
hydronium
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Dissociation of Water
scale measures hydrogen ion (H+)
concentration
 pH
Ranges from 0 to 14
 neutral = 7 (H+ = OH-)
 Below 7 = acid (more H+ than OH-)
 Above 7 = base (less H+ than OH-)
 Change of one pH unit is ten fold change
(gets 10x bigger/smaller)
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pH
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Acids
 Acids
dissociate in water to increase the
concentration of H+.
 Have
many H+ ions
 Sour taste
 HCl is hydrochloric acid or stomach acid
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Bases
combine with H+ ions when dissolved in water,
thus decreasing H+ concentration.
 Have many OH- (hydroxide) ions
 Bitter taste
 Laundry detergents
 Bases
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Buffers
- donating or removing H+ from solution to
neutralize acid or a base
 Offer protection from extreme pH levels
 Produced naturally by organisms:
 Organisms can’t tolerate much pH change
 Buffers maintain pH value of body fluids at
normal and safe level
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
Water transports molecules dissolved in it
 Blood, a water-based solution, transports molecules of
nutrients and wastes organisms
 Nutrients dissolved in water get transported through
plants
 Unicellular organisms that live in water absorb needed
dissolved substances
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