Studied by 17 peopleoxygen and hydrogen atoms
both are neutral
oxygen atoms have
8 protons, 8 electrons, and 8 neutrons
hydrogen atoms have
1 proton and 2 electrons
covalent bond
area of sharing, very strong bond in which atoms share electrons
covalent bond
negative ends attracted to positive ends
what makes h2o polar?
oxygen has more protons, so it will pull electrons towards itself
polar
a molecule having electrical poles (positive and negative ends)
nonpolar
a molecule that does not have positive and negative ends
where do hydrogen bonds exist?
between water molecules
hydrogen bonds
formed between the slightly (-) charge of the oxygen and the slightly (+) charge of the nearby hydrogen
when are hydrogen bonds weak?
when there are few
when are hydrogen bonds strong?
when there are many
what are the properties of water?
cohesion, adhesion, capillary action, specific heat, high heat of vaporization, water less dense as solid
cohesion
attraction between particles of the same substance (why water is attracted to itself)
cohesion occurs because of
water molecules forming hydrogen bonds with nearby water molecules
adhesion
attraction between two different substances
adhesion with water
water will make hydrogen bonds with other polar molecules (sugar) as well as with ions (salt)
capillary action
water molecules will "tow" each other along when in a thin glass tube
capillary action
is due to two forces-- adhesion (water molecules form hydrogen bonds to stick to the glass) and cohesion (water molecules form hydrogen bonds to each other to move up the capillary tube)
specific heat
amount of heat needed to raise 1 gram of a substance 1 degree celsius
specific heat with water
water resists temperature change both in heating and in cooling
specific heat with water
water can absorb or release large amounts of heat energy with little change in actual temperature
metal has a ____ specific heat
low
water has a ____ specific heat
high
high heat of vaporization
amount of energy to convert 1 gram of a substance from a liquid to a gas
water high heat of vaporization
in order for water to evaporate, hydrogen bonds must be broken (takes a lot of heat to do this). as water evaporates, it removes a lot of heat with it (why you cool down when you sweat)
water is less dense as a solid because
more molecules are in volumes of water than in the same volume of ice
water is less dense as a solid because
when frozen water forms, there is a crystal-lattice whereby molecules are set at fixed distances. there is a space of nothing inbetween molecules
suspension
don't dissolve but separate into tiny pieces (ex. milk blood)
solution
mixture of 2 or substances in which the molecules of the substances are evenly distributed
solutes
substance being dissolved
solvent
substance into which solute is being dissolved
what is the "universal solvent"?
water
ionic bond
strong attraction between positive/negative ions (salt)
what is an ion?
an atom that has gained (-) or lost (+) electrons
water is _____
polar
how does water dissolve salt?
water uses its (-) oxygen end to surround the (+) ions and its (+) hydrogen ends to surround the (-) ions
how does water dissolve salt?
it neutralizes the Na and Cl so molecules break off from salt crystals and dissolve
the pH scale
indicates the concentration of H+ ions
the pH scale
ranges from 0-14
on the pH scale, 7 is
neutral (# of H+ = # of OH-)
on the pH scale, 0-7 is
acidic (# of H+ > # of OH-)
on the pH scale, 7-14 is
basic (# of H+ < # of OH-)
each pH unit represents a factor of ___x change in concentration
10
strong acids have a pH of
1-3 (they produce lots of H+ ions)
the H+ ions formed in acids and the OH- ions formed in bases can cause
chemical reactions that may interfere with a cell's normal functioning (can lead to cell death)
stomach acid contains
hydrochloric acid (pH of 1-2) that causes chemical reactions with bacteria in food to kill them
buffers
weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH
buffers
produced naturally by the body to maintain homeostasis
how many hydrogen atoms are in a molecule of water?
2
how many oxygen atoms are in a molecule of water?
1
what holds the hydrogen atoms to the oxygen atom?
covalent bond
where is the majority of negative charge on the water molecule?
around the oxygen atom
what kind of charge would the oxygen atom have compared to the hydrogen atoms?
negative
what kind of charge would the hydrogen atoms have compared to the oxygen?
positive
how do nonpolar substances like fats, oils, and waxes interact with water?
they don't interact
hydrogen bonds can bond to
anything polar
atomic # is
number of protons in an atom
for an atom to be neutral,
first shell around an atom can hold ___ protons
2
second shell around an atom can hold ____ protons
8
third shell around an atom can hold ____ protons
8
H+
hydrogen atom
OH-
hydroxide atom
Note 
Flashcard (58)