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
