water & life (3) Flashcards
_… allows water molecules to form hydrogen bonds with each other
Polarity
The oxygen region of the h20 molecule has a … charge
partially negative
The hydrogen regions of the h2O molecule have a — charge
partial positive
A water molecule is a ___ molecule in which opposite ends of the molecule have ___ charges
polar
opposite
oxygen is __more/less__ electronegative than hydrogen
the polar covalent bonds spend more time near the… than the…
more
oxygen, hydrogen
Water molecule:
shaped like a ____
with its (number)… atom(s) and (number) ___ atom(s)
joined by _______ bonds
h2O
v
2 hydrogen, 1 oxygen
single polar covalent
four emergent properties of water that contribute to
Earth’s suitability for life
cohesive behavior
ability to moderate temperature
expansion upon freezing
versatility as a solvent
cohesion
collectively, hydrogen bunds hold water molecules together
Surface tension
a measure of how difficult it is to stretch or break the surface of a liquid
cohesion creates low or high surface tension
high
Adhesion
an attraction between different substances
ex. between water and plant cell walls
Helps counter downward pull ofgravity
cohesion contributes to
the transport of water and dissolved nutrients against gravity in plants
Holds water together while adhesion does its job
Kinetic energy
the energy of motion
water… heat to/from warm air and
absorbs
from
Releases stored heat to cooler air
Thermal energy
The kinetic energy associated w/ random motion of atoms or molecules
Temperature
represents the average kinetic energy of the molecules in a body of matter
heat
thermal energy in transfer from 1 body of matter to another
a calorie
is the amount of heat required to raise the temperature of 1 g of water by 1°C
amount of heat released from 1g of water by 1°C
“calories” on food packages is actually ___
Kilocalories
Joule is
another unit of energy
1J = ___ calories
0.239
1 cal= ___ J
4.184
specific heat of a substance is…
the amount of heat that must be absorbed or lost for 1g of that substance to change its temp by 1°c
1 cal/(g./°C)
water resists changing its temp bc
of its high specific heat
Water’s high specific heat can be traced to
hydrogen bonding
heat is absorbed whe(in water)
hydrogen bonds break
heat is released when
hydrogen bonds form
how is the air temp moderated in Coastal areas
a large body of water gathers heat during the day & summer, while only changing a few degrees, releasing it during the winter and night as the water cools
solution
a liquid that is a completely homogeneous mixture of substances
solvent
the dissolving agent of a solution
solute
the substance that is dissolved
aqueous solution
one in which water is the solvent
Why is water an effective solvent
it readily forms hydrogen bonds w/ charged and polar covalent molecules
a hydration shell
each dissolved ion (na and cl from NaCl) is surrounded by a sphere of water molecules
Hydrophilic substance
One that has an affinity for water
Hydrophobic substance
One that does not have an affinity for water
Lol molecules are hydrophobic because they have relatively more _____ bonds
Nonpolar
The major ingredients of cell membranes
Hydrophobic molecules
We use _____ to calculate the number of solute molecules in an aqueous solution
Mass
Molecular mass
The sum of all masses of all atoms in a molecule
1mol = _____x ____ molecules
6.02x 10^23
The number of molecules are usually measured un
Moles
1 mole = __ g
1
Molarity
The number of moles of solute per liter of solution
Hydrogen ion (H+)
The proton when a hydrogen atom leaves it’s electron behind and is transferred as a proton
Hydroxide ion (OH-)
The molecule that lost the (H+) proton
Hydronium ion (H3O+)
The molecule that gained the (H+) proton
Often represented as H+
pH scale
Describes whether a solution is acidic or basic
At equilibrium, the concentration of H+ and OH- is
10^-7 M (@ 25°C)
Acid
A substance that increases the H+ concentration of a solution
Base
A substance that reduced the H+ concentration of a solution
Hydrochloric acid
Strong acid
Sodium hydroxide
Strong base
Ammonia
Weak base
Carbonic acid
Weak acid
pH of acid solutions
Less than 7
pH of base solutions
Greater than 7
pH range for most biological fluids
6-8
The internal pH of most living cells is close to
7
The pH of human blood is close to
7.4
A person can not survive more than a few minutes if the pH of their blood
drops to 7 or rises to 7.8
Buffers
substances that minimize changes in concentrations of H+ and OH-
resists changes in ple when either are added to a solution.
Buffers typically consist of— that…
a weak acid and its corresponding base
accept & donate hydrogen ions to balance the pH.
carbonic acid (H3CO3)
formed when CO2 reacts with water in blood plasma
one importqant buffer in human blood and other biological solutions
how carbonic acid acts as a buffer
dissociates to yield bicarbonate ion (HCO3-) and a hydrogen ion (H+)
chemicla equilibrium between carbonic acid and bicarbonate acts as a pH regulator
the equilibrium shifts left or right as other metabolic processes add or remove h+ from the solution
