Water and Life Flashcards
Water chemical formula
H₂O
Water is a neutral molecule
(True or False)
True
Polar Molecule
A molecule in which the charges are unevenly distributed;
(Charges written parentheses (+) or (-) to show that the charges are weaker than ions) polar molecules attract each other because of their slight negative and positive charge
Why are water molecules considered polar molecules?
Water molecules are considered polar molecules because they consist of one oxygen atom (that has a stronger pull because it has more protons in the nucleus) and two hydrogen atoms (which have a weaker pull because it has less protons in its nucleus) This causes the oxygen molecule to get more electrons than the hydrogen atoms in the covalent bond, causing the oxygen molecule to have a slightly negative charge and the hydrogen molecules to have a slightly positive charge.
Hydrogen Bonding
Attraction of water molecules because of the slightly negative and positive charges of a water molecule; not as strong as covalent or ionic bonds (temporary)
What are the most common atoms involved in hydrogen bonding?
Oxygen, nitrogen, and fluorine
Cohesion
attraction between molecules of the same substance –> always through hydrogen bonds; creates a surface tension which allows some insects to walk on water
(Ex:water molecules)
Adhesion
attraction between molecules of different substances
(Ex: water molecules and glass molecules)
Capillary Action
One of the forces that draws water out of the roots of a plant and up into its stems and leaves. This is a combination of cohesion (which holds the water molecules together) and adhesion (which causes the water to rise)
Heat Capacity
the amount of heat energy required to increase an object’s temperature by 1 degree
Heat Capacity of Water
Water has a high temperature because it is highly cohesive.
Mixture
a material composed of two or more elements or compounds that are physically mixed together, but not chemically combined.
Types of mixtures
Solutions and Suspensions
Solution
a mixture in which all components are evenly distributed
(Ex: salt dissolving in warm water)
Suspension
mixtures of water and non dissolved material
(Ex: our blood is mostly water and suspended cells)
Solute
the substance that is dissolved
Solvent
the substance in which the solute dissolves
ph Scale
system used to indicate the concentration of H+ (hydrogen) ions in a solution. This system ranges from 0-14; below 7 the ph is acidic, at 7 the ph is neutral, above 7 the pH is basic.
the pH scale is logarithmic meaning each step represents a factor of 10 difference
Base
(aka proton acceptors) a compound that produces OH- (hydroxide) ions in a solution; pH above 7
Why are bases known as proton acceptors?
Bases are known as proton acceptors because they attract H+ ions to create water.
(look at example in notebook)
Buffer
weak acids or bases that can react with strong acids or bases to prevent sharp, sudden change in pH and maintain a specific pH –> extremely important for maintaining homeostasis because enzymes can only operate under certain conditions
Acid aka
proton donors
Why are acids considered proton donors?
Acids are considered proton donors because they give off H+ ions. These hydrogen ions are considered protons because to become an ion they need to get rid of the one electron in there valence shell.
One Universal Solvent
water
What can water dissolve/Why is it known as a universal solvent?
ionic compounds, other polar molecules
How does water dissolve compounds?
water molecules are attracted to positive/negative charge of other molecules (because of its bent shape) and pulls them apart, forming new compounds
What does water expand upon freezing?
Because when water drops in temperature, the hydrogen bonds push the H20 molecules farther apart from each other increasing the intermolecular space becuase there is air locked in by the crystal lattice structure, making it less dense than the water
Why is the heat capacity of water important
because if it was low, all the water in living organisms would evaporate on a hot day –> so it aids in regulating body temp
Do weak acids have a high amount of H+ or low
Low H+
Do strong acids have a high amount of H+ or low
High H+
Do weak acids have a high or low pH
high
Do weak acids have a low or high pH
low
pH equation
pH = -log[H+]
Why did the pH equation work
the pH equation works bc you are given molar concentration of H+ [H+] and since pH is logarithmic (to the 10th) doing -log cancels it
Acid definition
any compound that has H+
Acid
compounds that are acidic are corrosive and break down other compounds
pH range of acid
less than 7
Acid taste
sour
Bases make what type of solution
alkaline
Base taste + texture
bitter + slippery
Ionic bond
transfer of electrons; formed between anions and cations
Anion
negative ion
Cation
positive ion
Covalent bond
share electrons
single covalent bond
one pair of electron is shared
double covalent bond
two pairs of electrons are shared
Van der Waals forces
quick temporary forces where all electrons move to one side; the other side is positively charged, and a negatively charged is attracted to the positively charged side
Hydrogen Bond
weak chemical bonds that form when a H atom that is covalently bonded to an electronegtative atom is also attracted to another electronegative atom
When are H bonds strong
when there are alot of them –> like kindergarteners!
Surface Tension
measure of how difficult it is stretch or break the surface of a liquid
What is the importance of expansion upon freezing of water
when liquid gets cold and loses kinetic energy, the molecules usually come closer together; however, water does the opposite so that solid is les dense than liquid which allows marine life to live under ice
Why is the heat capacity of water so high
water is super cohesive so heat energy needs to break multiple hydrogen bonds before the heat spreads. (water needs to absorb more heat before it rises in temperature)
Kinetic Energy
energy of motion
more kinetic energy = faster or slower
faster
Thermal Energy
kinetic energy associated with random movement of atoms and molecules, taking volume into account
Temperature
average kinetic energy of the molecules in something that has matter regardless of volume
Relationship between thermal energy and volume
direct
Relationship between thermal and kinetic energy
direct
Relationship between kinetic energy and volume
no relationship
describe what happens in terms of thermal energy when a cold thing touches a hot thing
the thermal energy from the hot thing is absorbed by the cold thing until there is equilibrium
Heat
thermal energy transfer from one mass to another
Calorie
the amount of heat it takes to raise 1g of water by 1 degree celsius and the amt of heat released when 1g of water cools by 1 degree celsius
Kilocalorie
1000 cal is the amt of heat needed to raise 1kg of water by 1 degree celsius because of kilo
Joule
unit of energy
Specific Heat Capacity importance
1) regulate earth temp
2) survival of organisms
How does water help regulate the earths temp
it refulates coastal temps bc it can make air warmer at night and absorb heat when its too sunny
How does high specific heat capacity regulate body temp
bc humans are 75% of water so if it was low we would js evaporate and die
Vaporization
water -> gas (water vapor)
Vaporization aka
evaporation
Vaporization only happens at hot temps true or false
false it occurs at any temperature its js that at hotter temps the molecules are faster and the process is js faster
heat of vaporization
quantity of heat a liquid must absorb for 1g of it to be converted from liquid -> gas
What is the cause of the high heat of vaporization of water
the strongness of the multitude of hydrogen bonds bc they all need to break before l -> g
Does water have a high or low heat of vaporization
high
Why is waters high heat of vaporization important
1) moderate earth climate
How does the high heat of vaporization moderate earths climate
release heat at night, absorb in morning
Why is the high heat of vaporization bad for earth
causes burns from steam bc the liquid is even hotter when it condenses because energy is released bc g -> l is an exothermic reaction
Evaporative Cooling
when a liquid evaporates the liquid that is left behind doesn’t evaporate and instead it cools down
what is the cause of evaporative cooling
the molecules with the most KE (hot and fast) will evaporate and the warmer/slower ones will stay and then slow down when the high KE leaves
Why is evaporative cooling good
1) moderate water bodies temp
2) regulate bodies temp
How does evaporative cooling moderate water bodies temp
the top (surface) is hot bc sun and then when it evaporates the rest of the ocean slows down so that the whole ocean doesn’t poof into thin air
How does evaporative cooling regulate body temp
the hot sweat leaves the colder sweat behind so less KE so it cools u down bc it js gets colder
Why do people feel hotter when its humid
bc the hotter sweat cant leave bc the air is already filled with vapor
Hydration shell
the sphere of water molecules surrounding each dissolved ion of a solute
Why do ionic and molecular compounds dissolve in water
bc there can be polar regions and HYDROGEN bonds can pull stuff apart by the polar water molecules
Why does water dissolve salt and not the other way around
literally js bc theres more water -.-
Hydrophilic
like water
Hydrophobic
hate water
Example of hydrophilic thing
cotton
Examples of hydrophobic things
not polar or ionic and cant form H bonds
oil
Molecular Mass
sum of masses of all atos in a molecule
Avagadros number
6.02 x 10^23 formula units
Molarity
the # of moles of soluter per liter of solution
Molarity sumbol
mol
Molarity forumla
M = n/V
Aqueous solution
solution in which the solute is dissolved in water
Dissociate
pull apart to create ions
Acid Base Reaction
H2O + H2O ⇌ H3O+ OH-
Hydroxide ion is a base or acid
base
hydronium ion is acid or base
acid
H30+ = what ion
H+
In pure water the concentrations of hydroxide and hydronium are
equal
What is important about reversible reactions
they are at dynamic equilibrium which means there are equal concentrations and they move back and forth at a constant rate
Acid = proton ___
donor
Base = proton ____
acceptor
Acid
substances that add H+ to an aqueous solution by dissociating themselves
What makes strong acid strong
it dissociates completely in water
What makes a weak base weak
it does not completely dissociate in water
Base
substances that reduced the concentration of H+ by excepting H+ or dissociating OH-
Neutral Solution
solution where the concentration of H+ = OH-
What makes a neutral solution
strong acid and base
what makes a not neutral solution
weak acid and weak base
Not neutral solution
solytion where the concentrations of H+ do not equal OH-
In any aqueous solution at 25 degrees celsius, the product of H+ and OH- concentrations is constant at what
10^-14
pH scale
measure of H3O+ ions that compresses the range of H+ and OH- into logarithms
pH equation
ph= -log[H+]
Strong acid = ____ H+ = ____ pH
high low
Every step in the ph Scale is a factor of what
10
weak acid = ____ H+ = ____ pH
low high
If x< 7 is it an acid or a base
acid
If x> 7 is it an acid or a base
base
If x= 7 is it an acid or a base
neither its neutral
What are things that have a neutral pH
water
as you go up things get _____ acidic
more
as you go down things get more ___
basic
What substances are usually buffers
conjugate bases
How do buffers work
they accept or donate H+ when needed
Ocean acidification
when the pH of the ocean lowers
when CO2 dissolves in water and forms carbonic acid
Cause of ocean acidification
burning fossil fuels
Ocean acidification makes the ocean more
acidic
What particular ecosystem is ocean acidification detrimental for
coral reefs because they need carbonate to calcify –> this affects diversity in the ocean bc coral is super important
Ocean Acidification (chemically)
CO2 is absorbed by the ocean and it reacts with hydrogen to form carbonic acid
The carbonic acid decomposes into Hydrogen and bicarbonate
the hydrogen reacts with the carbonate and forms bicarbonate ion, so the carbonate ion decreases because there’s more hydrogen
How many bonds can a water molecule make
4
What kind of bonds are in adhesion
can be any doesnt just have to be hydrogen
