four , hydrogen
Each water molecule is joined to _____ other water molecules by ____ bonds
polar
The unequal sharing of electrons within a water molecule makes the water molecule _____.
electronegativity
The tendency of an atom to pull electrons toward itself is referred to as its _____.
evaporation
What process exerts the pull on water molecules that is relayed from leaf to root via cohesion?
1 calorie
The amount of energy that must be absorbed or lost to raise or lower the temperature of 1 g of liquid water by 1°C _____.
high specific heat
Because organisms are made primarily of water, they resist rapid temperature changes. This useful quality is based on water’s _____
an aqueous solution
Sodas typically contain sugar, flavorings, coloring agents, and carbon dioxide dissolved in water. The best term to describe this mixture would be _____.
increases the hydrogen ion concentration of an aqueous solution
An acid is a substance that _____.
A buffer resists change in pH by accepting hydrogen ions when acids are added to the solution and donating hydrogen ions when bases are added.
Select the statement that best describes a buffer.
can form between H and N.
Hydrogen bonds
(a) forces between atoms with partial charges.
(b) weaker than covalent bonds.
(c) important because they are numerous.
(b) weaker than covalent bonds.
(c) important because they are numerous.
Polar attractions are …
hydrogen
The partial negative charge at one end of a water molecule is attracted to the partial positive charge of another water molecule. What is this attraction called
the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus
The partial negative charge in a molecule of water occurs because _____.
compounds that have polar covalent bonds
Water molecules can form hydrogen bonds with _____.
non polar substances that repel water
Hydrophobic substances such as vegetable oil are _____.
hydrogen ions is equal to the concentration of hydroxide ions
In a neutral solution the concentration of _____.
water’s high surface tension
Which property of water allows a water strider to walk on water?
adhesion of water molecules to other kinds of molecules
Which property of water allows a paper towel to pick up a puddle of water?
the concentration of hydrogen ions in solution X is 1000 times as great as the concentration of hydrogen ions in solution Y
Consider two solutions: solution X has a pH of 4; solution Y has a pH of 7. From this information, we can reasonably conclude that _____.
They consist of weak acids and weak bases
Which statement is true of pH buffers?
Amino acid side chains have many carboxyl and amino groups
Which answer helps to explain why all living cells need pH buffers?
A- reacts with H+ to become HA.
A buffer consists of undissociated acid (HA) and the ion made by dissociating the acid (A-). How does this system buffer a solution against decreases in pH?
about half of the buffer molecules are dissociated.
Buffers work best when …
It’s the same reaction running backward or forward
How does the way a buffer stabilizes pH during addition of acid differ from the way the same buffer stabilizes pH during addition of base?
have a weak acid or a weak base half ionized in water.
To make a buffer, you need to …
absorption by the oceans of carbon dioxide generated by burning fossil fuels
What is the main reason that the oceans are becoming more acidic?
20 million metric tons
ow much carbon dioxide from the atmosphere is absorbed by the oceans on a daily basis?
carbon dioxide reacts with seawater, forming carbonic acid
What is the chemical reaction responsible for the oceans becoming more acidic?
Oyster larvae cannot grow shells in acidified ocean waters
How are oyster larvae affected by ocean acidification?
1. Corals and coral reefs are not able to form their hard skeletons
2. Clams, mussels, lobsters, and shrimp are not able to form strong enough shells.
2. Clams, mussels, lobsters, and shrimp are not able to form strong enough shells.
Which of the following are consequences of ocean acidification? Select all that apply.
shellfish
Because of ocean acidification, the price of which of the following foods is most likely to increase?
Stable hydrogen bonds keep water molecules of ice farther apart than water molecules of liquid water
Why does ice float in liquid water?
A raft spider can walk across the surface of a small pond.
Which of the following effects can occur because of the high surface tension of water?
The ocean near Portland moderates the temperature.
The cities of Portland, Oregon, and Minneapolis, Minnesota, are at about the same latitude, but Minneapolis has much hotter summers and much colder winters than Portland. Why?
has a heat of vaporization higher than that of most other substances
Liquid water
A lake heats up more slowly than the air around it.
Which of the following can be attributed to water’s high specific heat?
water molecules to form hydrogen bonds with each other
Polarity allows what
Cohesion
attraction between molecules of the same substance, transport of water and dissolved nutrients against gravity in plants
Adhesion
Attraction between molecules of the different substance helps counter the downward pull of gravity
surface tension
Cohesion of water molecules along a surface produces what
1. cohesion and adhesion
2. ability to moderate temperature
3. Expansion upon freezing
4. Versatility as a solvent
2. ability to moderate temperature
3. Expansion upon freezing
4. Versatility as a solvent
Four ways water properties contribute to life environment
High specific heat of water
What is temperature stability
temperature
Water can absorb or release a large amount of heat with only a s light change in its own…
acids
increase hydrogen concentration
bases
decreases hydrogen concentration
Buffers
pull from each one making it neutral
yes
Is ice less dense than water?
Solution
mixture of 2 ore more substances (ex: solute dissolved in a solvent)
Solute
substance that is dissolved in a solvent
Solvent
the substance in which a solute is dissolved
Soluble
molecules are hydrophilic
Insoluble
molecules are hydrophobic
acids
Proton donors
hydration shell
sphere of water molecules around each dissolved ion
true
True or false: Polar attractions are weaker than covalent bonds
Bases
Proton acceptors
acidic
less than 7
neutral
7
basic
more than 7
buffers
weak acids and bases
true
True or False:
bases will give off O ions to make it more basic, H ions to make it more acidic
bases will give off O ions to make it more basic, H ions to make it more acidic
Polar covalent bonds
Oxygen is more electronegative than hydrogen, so the electrons of the covalent bonds spend more time closer to oxygen
Polar molecule
overall charge is unevenly distributed
Kinetic energy
Anything that moves
Thermal energy
kinetic energy of motion with random movement of atoms or molecules is…
Temperature
this represents average K.E. of molecules in a body of matter
Hydrophilic
any substance that has an affinity of water is said to be hydrophilic
Hydrophobic
Nonionic/nonpolar (cannot form hydrogen bonds)
vegetable oil
An example of Hydrophobic is
Molecular Mass
sum of the mass of all the atoms in a molecule
a mingling of molecules and/or ions
Dissolving is best described as ..
(a) hydrogen atoms
(b) oxygen atoms
(b) oxygen atoms
Water is a source of ______________ for chemical reactions in cells
hydrogen bonds between surface water molecules resist being stretched.
Water has surface tension because …
A water molecule can make 4 hydrogen bonds
Which of the following helps most to explain why water has a high specific heat?
1. Molecules collide with varied angles and speeds.
2. Hydrogen bonds are relatively weak.
2. Hydrogen bonds are relatively weak.
Which factor is important in making it possible to cool yourself by sweating? Think carefully!
it takes energy to break hydrogen bonds
Though you add heat, the temperature of boiling water remains constant because …
(a) Water molecules make hydrogen bonds at definite angles.
(b) Cold molecules move less than warm molecule
(b) Cold molecules move less than warm molecule
Which statement helps to explain why ice is less dense than liquid water?
aquatic life to exist at the North Pole
The open spaces in water’s crystal structure make it possible for …
Polar molecules attract one another.
Why doesn’t oil mix with water?
(a)It results from hydrogen bonding.
(b) It helps to pull water through plants.
(c) It involves both cohesion and adhesion.
(b) It helps to pull water through plants.
(c) It involves both cohesion and adhesion.
Which statement is true of water’s tensile strength?
Polar groups attract one another.
Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface?
Seawater will become more acidic, and carbonate concentrations will decrease.
Increased atmospheric CO2 concentrations might have what effect on seawater?
