Based on the method by which they
get food, organisms are classified as
autotrophs or heterotrophs. Which
organism listed below is correctly
paired with its metabolism?
Orchids were studied to determine if
the amount of humidity affected the
flowering of these plants. Which of
these was the independent variable
in this study?
A The percentage of humidity
B The amount watered
C The length of time required for flowering
D The number of flowers on each plant
An experiment was designed to determine the
effects of cool temperatures on the germination
of piñon pine seeds. Which of these variables
was LEAST important to control in this
A The brand name of the refrigerator used to
produce the cool temperatures
B The number of seeds used in each group
C The amount of time that the seeds were
exposed to cool temperatures
D The temperature range used to define cool
PROPERTIES OF WATER
The most abundant compound in living things.
Expands as it freezes.
Ice is less dense than liquid water so it floats in
water. Think about importance- polar bears
Other Useful Info on Water
The 2 to 1 ratio of hydrogen to water
remains the same, no matter what
Polar nature of water allows it to be the
The low density of water in its solid state
(ice) allows for organisms to survive cold
What characteristic of water remains the
same no matter what is dissolved in it?
A. The ratio of hydrogen to oxygen
B. The ability to refract light
C. The hydroxide ion concentration
D The freezing temperature
Fish survive through severe winters because of the
property of water that allows water to —
A. form chemical bonds as it freezes, raising the
water temperature below the ice
B. increase in density while it freezes, dissolving
more oxygen from the air
C. expand when it freezes, creating a floating and
insulating layer of ice
D. precipitate vital nutrients when it freezes,
increasing the food supply
If the properties of water were to change so that the
solid form was denser than the liquid form, organisms
living in a cold pond environment would be less likely
to survive because water would no longer —
A. dissolve enough oxygen from the air
B. produce solutions containing vital nutrients
C. remain neutral, instead becoming highly acidic
D. produce a floating insulating layer of ice
Polar Molecule – A covalently bonded
molecule where the e- are shared unequally
causing the two ends to be oppositely charged.
Weak attractions between polar ends of
different water molecules (H+ and O-)
***Think of each water molecule being a tiny
magnet that attracts other water molecules
and/or other different molecules
Causes cohesion and adhesion.
NOT A “BOND”
COHESION vs. ADHESION
Cohesion – attraction
between one molecule of
water to other molecules of
n i.e. water droplets – “beads up”
Adhesion – attraction between
molecules of different
n i.e. capillary action – H2O
attracted to glass or tissue
(meniscus and plants)
n Water droplets sticking to the side
of a car window
Cohesion, Adhesion or Both?
Examining the pictures, explain which
water property or properties is occurring.
The unique properties of water
enable life to exist on Earth. Which
of these is a property of pure water?
A. Its solid form is more dense than its
B. It has a low heat absorption capacity.
C. It is slightly more acidic than air.
D. It dissolves many substances.
Which factor makes water an effective
A. The presence of molecular oxygen
B. Its lack of covalent bonds
C. The polar nature of its molecules
D. Its abundance on Earth’s surface
Two or more elements or compounds that
are physically mixed
NOT chemically mixed!!!!!
n i.e. salt/pepper, iced tea
Water can form 2 types of mixtures:
A mixture in which molecules are evenly
n Solute – substance being dissolved
n Solvent – substance doing the dissolving.
A mixture in which materials are NOT dissolved
in water and separate or settle out.
n i.e. blood, salad dressing, snow globe
Two clear solutions are placed in
separate beakers. The first solution has
a pH of 4, and the pH of the second
solution is unknown. If the two solutions
are mixed and the resulting pH is 5, the
second solution must have –
A Fewer suspended solids
B A lower temperature
C More dissolved salt (NaCl) particles
D A higher concentration of OH- ions