Unit 2 Flashcards
polar molecule
a molecule that’s overall charge is unevenly distributed
polarity of molecules
oxygen part is slightly negative, hydrogens are slightly positive
- allows water particles to be held together by hydrogen bonds
- high surface tension
Properties of Water
- Polar
- Cohesion of Water Molecules
- Moderation of Temperature
- high specific heat
- high heat of vaporization
- Ice less dense than liquid
Cohesion
linking together of molecules of the same substance by hydrogen bonds
Cohesion of Water Molecules
- along with adhesion allows water to be transported against gravity in plant
- great surface tension
Surface tension
a measure of how difficult it is to sketch or break the surface of a liquid
Heat
a measure of the matter’s total kinetic energy due to motions of its molecules
-depends on volume
Temperature
measure of heat intensity that represents the average kinetic energy of molecules
calorie
the amount of heat it takes to raise the temp of 1g of water 1 degree Celsius .
specific heat
the amount of heat that must be absorbed or lost for 1g of that substance to change 1 degree Celsius
Water’s high specific heat
- water’s temp will change less when it absorbs or loses heat
- high because hydrogen bonds are first formed or broken by energy before the kinetic energy of the molecules are affected
- keeps temp fluctuations on land and water within limits that permit life
- allows organisms (who are made up mostly of water) to resist changes in their own temp
Heat of Vaporization
the quantity of heat a liquid must absorb for 1g of it to be converted from liquid to gas
-water high level: helps moderate Earth’s climate
evaporative cooling
as a liquid evaporates, the surface of remaining liquid cools (hottest molecules evaporate)
- contributes to stable temps in lakes and ponds
- prevents terrestrial organisms from overheating (evaporation from leaves, sweat)
Floating of Ice on Liquid water
- one of few substances that are less dense as a solid than a liquid
- ice molecules each hydrogen bonded to 4 neighbors in spacious crystal
- ice insulates liquid water below, preventing it from freezing and allowing life to exist under the surface
- provides solid habitat for some animals
aqueous solution
a solution in which water is the solvent
hydration shell
water molecules surround dissolved ions forming a sphere
hydrophilic
any substance that has an affinity for water
colloid
a stable suspension of fine particles in a liquid
hydrophobic
substances that are non-ionic and non polar and seem to repel water
molecular mass
sum of the masses of all atoms in a molecule
mole
equal to the molecular mass, the amount of a substance that contains 6.02x10^23 molecules
molarity
the number of moles of solute per liter of solution
hydrogen ion
H+ a single proton with charge of 1+
hydroxide ion
OH- charge of -1
hydronium ion
H3O+ represents by H+
acid
a substance that increases the hydrogen ion concentration of a solution
acidic solution
a solution that has more H+ than OH-
base
a substance that reduces the hydrogen ion concentration of a solution
basic solution
more OH- than H+
The PH scale
-at room temperature 25 C:
- [H+][OH-]= 10^-14
pH= -log[H+}
- less than 7 equals acid 7= neutral greater than 7 basic
Buffers
a substance that minimizes changes in the concentrations of H+ and OH- in a solution
- accepts excess H+ or donates H= when developed from a solution
- carbonic acid (H2CO2) is one found in blood
- often acid base pairs
ocean acidification
occurs when CO2 dissolves in seawater, reacts and forms carbonic acid, lower pH
-limits calcification (which is important for coral reefs)
acid precipitation
refers to rain, snow, or fog with a pH lower than 5.2
carbon
has 4 valence electrons and shares these electrons to get 8 valence electrons
- when 4 single bonds are formed the molecule forms a tetrahedral shape
- two carbons that have a double bond form a flat rectangular shape
organic molecules
made up mostly of carbon, hydrogen, oxygen, and nitrogen
Carbon skeletons can vary in;
length, branching, double bond position, presence of rings
hydrocarbons
organic molecules consisting of only carbon and hydrogen
- major components of petroleum
- many of cells organic molecules have regions of hydrocarbons, ex. fat molecules tails
- relatively nonpolar, often behave hydrophobically
- can undergo reactions that release large amounts of energy
Isomers
compounds that have the same number of atoms of the same elements but different structures and thus different properties
structural isomers
differ in the covalent arrangements of their atoms and the location of double bonds
cis-trans isomers
carbons have covalent bonds to the same atoms but these atoms differ in their spatial arrangement due to the inflexibility of double bonds
- cis isomer; both x atoms on the same side of the double axis
- trans isomer; x’s on opposite sides
Enantiomers
isomers that are mirror images of each other and that differ in shape due to the presence of an asymmetric carbon
-can cause drugs to have different effects
asymmetric carbon
a carbon that is attached to four different atoms.
