Properties of water Flashcards
substance that makes all life possible
water
All familiar organisms are made mostly of
water
water is the Only substance to exist in
all three states
Water’s unique behavior is related to its
structure and interaction of it’s molecules
water molecule shape
a wide V with two hydrogen atoms joined to the oxygen atom by single covalent bonds
properties of water come from the
attractions between oppositely charged atoms of different molecules
hydrogen bond
The hydrogen of one water is attracted to the oxygen of another
In the liquid form, hydrogen bonds are
fragile
why are hydrogen bonds fragile
They form, break and reform very frequently
which atom is is more electronegative in water
oxygen
what does it mean that oxygen has a higher electronegativity
electrons in the covalent bond spend time closer to it
The oxygen region has a partial
negative charge
the hydrogen region has a
partially positive charge
The overall charge of water is unevenly distributed because
unequal sharing of electrons
Four emergent properties of water
- Cohesive behavior
- Ability to moderate temps
- Expansion upon freezing
Versatility as a solvent
Cohesion of water molecules
the molecules stay close together because of the hydrogen bonding
cohesion contributes to what in plants
transport of water and dissolved nutrients against gravity
hydrogen bonds cause water molecules to do what in plants
water molecules in veins to tug on those farther down
Adhesion
the clinging of one substance to another
adhesion in plants
Adhesion of water by hydrogen bonds to molecules of the cell walls counters the downward pull of gravity
surface tension is related to
cohesion
surface tension
Measure of how difficult it is to stretch or break the surface of a liquid
water has a ______ surface tension
high
why does hydrogen have a high surface tension
hydrogen bonding between the molecules of the air and water below
how does water moderate air temps
by absorbing heat from warmer air and releasing stored heat to colder air
why is water an effective heat bank
can absorb or release a large amount of heat with only slight changes in own temp
why does a desert have huge temp changes
there is no water to moderate the temp
places closer to the ocean will have ____ temp fluctuations
less
When two objects of different temps are brought together, the
Thermal energy passes from the warmer object to the cooler one
when does the thermal energy stop passing from the warmer object to the cooler one
when they are the same temp
Molecules in cooler objects
Speed up at the expanse of the thermal energy of the warmer object
Kinetic energy:
The energy of motion
. Anything that moves has this energy
kinetic energy
The faster the movement the greater the
kinetic energy
Thermal energy
Kinetic energy associated with the random movement of atoms or molecules
thermal energy reflects
total kinetic energy
Temperature
The average kinetic energy of molecules in a body of matter
does volume matter for temp
nope
Heat
Thermal energy transferred from one body of matter to another
heat is measured in
Joules
1 cal
4.184 J
heat is also measured in
calories
calories
. Heat needed to raise the temp of 1 g of water by 1 degree Celsius
Water’s high specific heat has the ability to
stabilize temps
why can water stabilize temps
because of it’s relatively high specific heat capacity
Specific heat
- The amount of heat that must be absorbed or lost for 1 g of that substance to change temps by 1 degree Celsiu
Water has a specific heat of
4.18
Water changes it’s temp less than other liquids when it
absorbs or loses heat
water loses a _____ amount of water with each degree of change
large
The high specific heat of water can be traced to the
hydrogen bonds
To beak hydrogen bonds,
heat must be absorbed
when hydrogen bonds form they
release heat
before a water molecule can move faster
the heat goes towards disrupting the hydrogen bonds
When water temp drops slightly
releases large amount of energy in HEAT
what is the relevance of water’s specific heat capacity
Large body of water
a. Can absorb and store huge amounts of heat from the sun
b. Only warms up a few degrees
high specific heat capacity of water creates
a favorable environment for marine life
Evaporative cooling
Liquid evaporates and the surface left behind cools down (temp decreases)
the hottest molecules are the most likely
to become gas
evaporating cooling contributes
to the stability of temps in lakes and ponds
a mechanisms that prevents the organism from overheating
Molecules stay close together because
they are attracted to one another
Molecules must moving fast enough
overcome these attractions
VAPORIZATION or EVAPORATION
Depart the liquid phase and enter the air as gas
even at the low temps, the speediest molecules can
escape into the air
Heat of vaporization
- Quantity of heat a liquid must absorb for 1 g to be converted from liquid to gas
water has a ____ heat of vaporization compared to other liquids
high
heat of vaporization is an emergent property from
strength of hydrogen bonds
what must be broken before the molecule can exit liquid stage into the water vapor
the hydrogen bonds
Water is one of the few substances that is ____ dense as a solid than a liquid
less
what does water do when it solidifies
expands
what causes this expansion as water turns solid
the hydrogen bonds
when water is at a temp above 4 degree Celsius
Water is like any other liquid
Temps from 4 degree Celsius to 0 degree Celsius
Water begins to freeze as more and more of it’s molecules are moving too slowly to break hydrogen bonds
At 0 degree Celsius
Molecules become locked together in a crystalline lattice
Hydrogen bonds keep the molecules _____ apart than at 4 degree Celsius
farther
When ice absorbs enough heat for the temp to rise above 0 degree Celsius
Hydrogen bonds between molecules are shattered
At 4 degree Celsius water has reached
its greatest density
floating ice on water allows the liquid below to be
insulated and stops it from freezing
how is Global warming affecting ice
a. Ice has formed later in the year and melts earlier
b. It covers a smaller area
why is Water a very versatile solvent
polarity of water molecules
A compound does not need to be _____ to dissolve in water
ionic
how do non-ionic molecules dissolve in water
water molecules surround each of the solute molecules and form hydrogen bonds with them
Large molecules like proteins can dissolve in water if
they have polar regions on their surface
Solution
- A liquid that is a completely homogeneous mixture of two or more substances
Solvent
Dissolving agent of a solution
Solute
- Substance that is dissolved
Aqueous solution
The solute is dissolved in water
Hydration shell
The sphere of water molecules that surround a dissolved ion and prevent those ions from rejoining together
Working inward, water will eventually do what to the ions
dissolve them all
Hydrophilic
- Any substance that has an affinity (liking) for water
can something be hydrophilic without dissolving in water
yes, think of a cotton towel
Hydrophobic
- Substances that are non-ionic and non-polar (can’t form hydrogen bonds)
Molecular mass
Sum of the mass of all atoms in a molecule
Mole (mol)
6.02 x 10^23
6.02 x 10^23 daltons in
1 gram
Moles of one substance equals the same number
MOLECULES as a mole of another substance
Molarity
Number of moles of solute per liter of solution
a hydrogen atom can shift between
two water molecules during a hydrogen bond
Hydrogen ion (H+)
A single proton with a charge of 1+
H+ does NOT exist on
its own in an aqueous solution
h+ Always associated with a water molecule in the form
H3O
Hydroxide ion (OH-)
The water molecule that lost a proton
Dissociation of water importance
H+ and OH- are very reactive and concentration changes can affect a cell’s proteins
in pure water, H+ and OH- are
equal in concentration
Acids
donate H+ ions when dissolved in water
Substance that increases the hydrogen ion concentration of a solution
acid
An acidic solution has more
H+ to OH-
Base
- Reduces the hydrogen ion concentration of a solution
Some bases reduce H+ concentrations directly by accepting Hydrogen ions
Ammonia
Other bases reduce H+ concentration indirectly by dissociating to form hydroxide ions
Sodium hydroxide
Basic solutions
Have a higher concentration of OH- than H+
Neutral solutions
Solutions that have equal H+ and OH-
Strong Base and acids
Compounds that dissolve completely when mixed with water
what is not a reversable reaction when used
Strong Base and acids
The reaction is reversible when using
Weak acid or base
The PH scale
Compresses the range of H+ and OH- concentrations by logarithms
each jump in the PH scale is a jump in
ten
EXAMPLE
Ph of 3 to PH of 6
It is a thousand times more acidic (10 x 10 x 10)
PH formula
PH = -log [H+]
Ph _____ as H+ concentrations increase
declines
Neutral solutions formula
-log 10-7 = -(-7) = 7
PH above 7
Basic solutions
PH of less than 7
Acidic solution
An acid not only adds hydrogen ions to a solution but it also
removes hydroxide ions
A base increases OH- concentrations but also
reduced H+ concentrations by the formation of water
Buffers
substance that minimizes changes in concentrations of H+ and OH- in a solution
buffers must be
weak acids and its corresponding base
how do buffers work
- Buffers accept hydrogen ions from the solution when they are in excess
- Donate hydrogen ions to the solution when there aren’t enough
