Chapter 3: Water Flashcards
The polarity of water molecules results in:
hydrogen bonding (polar covalent bonding)
The _____ of water molecules results in hydrogen bonding
polarity
T/F Hydrogen bonds are 1/10th as strong as covalent bonds
False. Hydrogen bonds are 1/20th as strong as covalent bonds
Are covalent bonds stronger than hydrogen bonds?
yes
What is the cohesion attraction at the water surface?
a. Surface tension
T/F Covalent bonds are stronger than hydrogen bonds
True
Cohesion:
______ tension
Water from roots can reach leaves
surface
Clinging of one substance to another
adhesion
Water molecules stay close to each other as a result of hydrogen bonding to hold the substance together
Cohesion
This is how water from roots can reach leaves
cohesion
A measure of how well molecules stick to each other or group together. Caused by the attractive forces between like molecules.
Cohesion
1 calorie is the amount of ___ ____ needed to raise the temp. of 1 g of water by 1 degree celsius
heat energy
The specific heat of fusion is the heat energy needed to take ____ from 0 degrees C to 0 degrees _____
ice, water
A water spider can raise along the surface of the water. What force is at work that allows him to do it?
Surface tension (caused by cohesion - hydrogen bonding)
The amount of heat that must be ABSORBED or LOST for 1 g of that substance to change its temperature by 1 degree celsius
specific heat of a substance
Surface tension is caused by:
cohesian
Water from the roots of a tree can reach the leaves. What is this caused by?
Cohesion
The specific heat of water
1 cal / 1 g / 0 c
Specific heat of alcohol
0.6 cal / 1 g / 0 c
Coastal regions have more mild climates than inland regions do.
True
Coastal areas have milder climates than inland regions. What factor majorly causes this phenomena?
High specific heat of water
If organisms are made of a liquid with a higher specific heat….
they are more able to resist changes in their own temperatures than if they were made of a liquid with a lower specific heat
The transformation from a liquid to a gas
Evaporation
The quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gas phase:
Heat of vaporization
Regarding heat of vaporization, the quantity of heat that a liquid must absorb causes how much of the liquid to be converted from the liquid to the gas
1 g
T/F as a liquid evaporates, the surface of the liquid that remains behind cools down
true
1 g of water at 25°C needs 580 cal of heat, much higher than _______
alcohol (so water has a higher heat of vaporization - more resistant to changes in temperature and less evaporative)
What, as mentioned in the lecture, contributed to the stability of lake temperatures?
evaporative cooling
You are a scientist who is studying a freshwater lake in Oregon. You notice that the lake consistently has a temperature of approx. 55 degrees C. What is this most likely due to?
Evaporative cooling
________ of water from the leaves of a plant helps the tissues in the leaves from becoming too warm in the sunlight
evaporation
Evaporation of sweat from the human skin has what effect?
Dissipates body heat
T/F Evaporation does not prevent terrestrial organisms from overheating
False
Why is ice less dense than liquid water?
Stable hydrogen bonding occurs between hydrogen atoms in ice (where as in water, the bonds are breaking and reforming)
Ice is less dense than water due to _______ _______
hydrogen bonding
T/F Ice is more dense than liquid water due to hydrogen bonding
False
Ice floats on top of water because of….
hydrogen bonding (stable hydrogen bonding between hydrogen elements in ice)
At 0 C, water molecules become locked into a ____ ____. Each water molecule is hydrogen-bonded to ____ partners
crystalline lattice, four partners
T/F Each water molecule in ice is hydrogen-bonded to four partners
True
Liquid water is always at a state of dynamic adjustment, so it doesn’t have a chance to be locked into a ____ ____
crystalline lattice
With ice, below 4 degrees celsius, the amount of heat energy is minimal and the weaker partial charges even out and create a ____ lattice: less dense
crystalline
At _______ Water behaves like other liquids, expanding as
it warms and contracting as it cools
4 degrees celsius
At _______ Water molecules become locked into a crystalline lattice, each water molecule hydrogen-bonded to four partners
0 degrees celsius
When ice is warmed to 4 degrees celsius, what do you expect to happen?
Water behaves like other liquids. It will expand when warmed and constrict when cooled.
At 0 celsius, hydrogen bonds keep molecules at “arm’s length,” far enough apart to make ice about ______ less dense than liquid water at 4 degrees celsius.
10% less dense
T/F Floating ice insulates the liquid water below, preventing it from freezing and allowing life to exist under the frozen surface
True
A dissolving agent
solvent
Substance that is dissolved
solute
Liquid that is a completely homogenous mixture of two or more substances
Solution
Sphere of water around each dissolved ion
hydration shell
T/F A solution MUST be homogenous for it to be a true solution
True
2 types of molecules that are water-soluble
ionic or non-ionic polar molecules
Solvent
a dissolving agent
Solute
substance that is dissolved
Solution
a liquid that is completely homogenous mixture of two or more substances
Hydration shell
sphere of water molecules around each dissolved ion
These molecules are water-soluble:
ionic or non-ionic polar molecules
Has an affinity for water
hydrophilic substances
hydrophilic substances have a….
affinity for water
What substances have an affinity for water?
hydrophilic substances
A mixture of suspended molecules
colloid
A colloid is ____ but has very big molecules such as cellulose (cotton)
hydrophilic
Is a colloid a stable or unstable suspension of fine particles in a liquid?
A colloid is a stable suspension of fine particles in a liquid
T/F a colloid is made up of molecules or compounds
molecules
Nonionic and non-polar substances
hydrophobic
What two types of substances are likely to by hydrophobic
nonionic and non-polar substances
Cell membrane components are what type of substances (mentioned in lecture)
hydrophobic (outside) and hydrophilic (inside)
Oil is a _____ or _____ substance. This explains why you see two layers in salad dressing.
Hydrophobic
Cell membrane components are hydrophobic. For example. The inside of the cell membrane contains the ______ tails but the lipid ____ are facing out towards the exterior water
hydrophilic, hydrophobic heads (water does not free flow in and out of cells)
Define molecular weight.
____ g/mol
the number of atoms or molecules in one mole of a substance
6.023x 10^23 atoms/molecules
the concentration of a solution expressed as the number of moles of solute (m) per liter of solution (L)
molarity (m/L)
You have 1 mole of of hydrogen atoms. How many atoms do you have?
6.023x10^23
molarity is the number of moles of solute dissolved per liter of solution (m/L) . Molality is then the number of moles of solute per kilogram of the SOLVENT, NOT solution! (mol solute / kg solvent)
Molality units:
mol solute / kg solvent
T/F Molality deals with mass and molarity deals with volume
True
Molality:
moles of solute / kg solvent
A substance that increases the hydrogen ion in a solution
acid
Name on strong acid (disassociation reaction) mentioned in lecture
HCL - H+ and Cl-
The higher the _____, the lower the PH number
acidity
Ph of 8 means the solution has _____ hydrogen ions in solution than in a solution with a PH of 12
less
The specific disassociation reaction of a weak acid (mentioned in lab)
H2C03 -> HCO3- + H+
What is the basic difference between strong and weak acids:
partial vs. complete disassociation
Know the logarithmic laws:
PH = - log [H+]
pOH = - log [OH-}
A pH unit represents a ____ difference in H+ and OH- concentrations
tenfold
A _____ is a substance that minimizes the changes int he concentrations of hydrogen ions
buffer
Strong alkali vs. Weak alkali
NaOH —-> Na+ and OH-
NH3 + H+ —–> NH4+
Draw out the reaction which the PP mentioned as part of the buffer concept
H2CO3 ⇔ HCO3- + H+
Addition of a buffer (acid): if pH rises, the reaction will proceed to the….
right
Addition of a buffer (base): if pH drops, the reaction will proceed to the…
left
A substance that reduces the hydrogen ion in solution
base
H2C03 —> HCO3- + H+ is an example of a…
weak acid
Know the PH scale
….
List two threats to water quality on earth
a. acid precipitation (rain, snow pH < 5.2)
b. CO2 in the air (greenhouse effect)
In acid precipitation, rain, snows or fog have a pH ____ than what?
less than 5.2
The green house effect is due to what non-polar compound in the atmosphere
CO2 (linear)
