biology properties of water

rowlands test 11/17

oxygen 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,

# of protons has to = # of electrons

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