2 Water as a vehicle for life Flashcards
hydrogen bonding
attraction between H atom in a polar covalent bond and another electronegative atom
Oxygen
stronger attraction for electrons (more electronegative-pulls electrons toward it)
solution
liquid that is a homogenous (of the same) mixture of substances
solute
dissolving agent of a solvent and a substance which is dissolved
aqueous solution
water is the solvent (each ion is surrounded by a hydration shell)
hydration shell
the sphere of water molecules around each dissolved ion
Cations
- positive ions
- oxygen closet
anions
- negative ions
- hydrogen closet
Water as a solvent can dissolve many types of solutes:
- Ionic molecules
- compounds made of non-ionic polar molecules
- large polar molecules (ex. proteins) if they have ionic and polar regions
hydrophilic substance
has an affinity for water (relatively polar bonds)
hydrophobic substance
does not have an affinity for water (relatively non-polar bonds)
H-bonding in ice is more ordered than in liquid water because…
- ice is less dense than water
- ice is solid and has a larger volume
freezing point depression
presence of solutes decreases the freezing point of a solvent (seawater)
Hydrogen bonds are constantly…
breaking and reforming
What can high concentrations of solutes in some organisms do in cold climates?
can prevent body fluids from freezing
Glycerol concentration in smelt blood (plasma)….
increases as temperature decreases
liquid water
hydrogen bonds break and reform
ice
hydrogen bonds are stable
are cohesion and adhesion important in water transport in plants?
Yes
Cohesion
sticking together (the hydrogen bonds hold the substance together)
Adhesion
the clinging of one surface to another
adhesion of water by hydrogen bonds to the molecules of cell walls helps counter the downward pull of gravity
as a result of hydrogen bonding what do water molecules do?
they stay close to each other
surface tension
how hard it is to break the surface of a liquid
Surface tension is high in water due to..
its cohesive behaviour. At the interface b/t water and air is an ordered arrangement of water molecules, hydrogen-bonded to on another and to the water below. this gives water an unusually high surface tension, making it behave as though coated with and invisible film. (water above the rim of a glass)
does water has a high specific heat?
Yes
What is the amount of heat to change temperature?
1 gram, raised by 1 degree celsius
Calorie
the amount of heat it takes to raise the temperature of 1 g of water by 1 degree celsius
specific heat of a substance is defined as..
the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 degree celsius (cal/g/degrees c)
To change the temperature of something what do we apply?
heat
temperature
the intensity of heat
thermal energy
amount of kinetic energy due to molecular motion
what happens because of the high specific heat of water relative to other materials…
water will change its temperature less than other liquids when it absorbs of loses a given amount of heat (pot heating before the water inside)
Heat of vaporization
quantity of heat of liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state (large quantity of heat must be absorbed)
What happens as liquid evaporates?
remaining surface cools
Evaporative cooling helps stabilize temperature in organisms and bodies of water…
ex. a dogs tongue
Ocean absorbs heat from warmer air and releases stored heat to cooler air (only slight change in water temp.)
water has a high…
specific heat and heat vaporization relative to most other liquids
how much heat is need to evaporate 1g of water at 25 degrees Celsius?
2427 Joules (double is need for alcohol or ammonia)
What bond must be broken before the molecules can make their exodus from the liquid?
hydrogen bonds
H2O molecules dissociate the same rate at which…
they are being reformed
When is there fewer fluctuation?
when there is a body of water near by
acid
donates a proton to a solution, increases H+ concentration of a solution (gives)
Base
accepts a proton from the solution, decreases H+ concentration of a solution (receives/accepts)
Neutral solution
equal number of protons and hydroxide ions
acidic solution
has more H+ than OH-
Hydrogen leaves its electron behind…
therefore transferred as a proton (H+ ion)
molecules that lost H-1 becomes OH-
basic solution
has more OH- than H+
[H+][OH-]=10^-14
in any aqueous solution at 25 degrees C, the product of the H+ and OH- concentrations is constant at 10^-14
p=-log[H+] (log base 10)
pH of a solution is defined as the negative logarithm (base 10) of the hydrogen ion concentration
What would a neutral solution be using the pH scale?
7
pH declines as…
H+ concentration increases
most biological fluids are… (pH)
within the range of pH6-8 (human stomach is the exception with about a pH2)
Changes in pH can drastically affect….
the chemistry of a cell
Buffers
minimize changes in concentration of H+ and OH- in a solution
(acid-base pair that reversibly combines with H+ (it does so by accepting hydrogen ions from the solution when they are in excess and donating hydrogen ions to the solution when they have been depleted.
Most buffer solutions contain a weak acid and its corresponding base, which combine reversibly with hydrogen ions.)
buffering in biological systems: EX
CO2->H2O
H2CO3
HCO3-
acts as buffers in your blood
pH rises
less H+ in solution
pH falls
more H+ in solutions
When air pollutants mix with water in atmosphere what happens?
decreases pH
can fall at some distance
Ocean water quality is at risk because..
when CO2 dissolves in seawater it reacts with water to form carbonic acid, which lowers ocean pH, a process known as ocean acidification, coral reefs are avery sensitive therefore this causes a decrease in the ability of corals to form calcified reefs)
