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Flashcards in Chapter 3 Deck (67):
1

How much of Earth's surface is covered in water?

3/4s

2

What is water's molecular shape and why?

wide V, because oxygen is more electronegative than hydrogen, causing polar covalent bonds = polar molecule

3

charges of oxygen and hydrogen?

oxygen= slightly neg
hydrogens = slightly pos

4

properties of water due to:

attractions --> hydrogen bonds

5

____ _____ bonds in water molecules result in hydrogen bonding.

polar covalent

6

four key properties of water

cohesive behavior
ability to moderate temperature
expansion upon freezing
versatility as a solvent

7

cohesion

collective hydrogen bonds that hold substance together
contributes to transport of water and dissolved nutrients against gravity in plants (eg. hydrogen bonds cause water molecules leaving veins of leaf to tug on molecules further down)

8

adhesion

clinging of one substance to another
helps counter downward pull of gravity of water to molecules of cell walls

9

surface tension

measure of how difficult i tis to stretch/break the surface of a liquid
hydrogen-bonds between water molecules give it a high surface tension

10

How does water moderate temperature?

It absorbs heat from warmer air and releases stored heat to colder air
Can absorb relatively large amount of heat with only a slight change to its own temp

11

kinetic energy

energy of motion
faster a molecule = greater KE

12

thermal energy

related to temperature; KE associated w/ random movement of atoms/molecules

13

temperature

measure of energy that represents the average KE of the molecules in a body of matter, regardless of volume

14

total thermal energy

depends on matters' volume

15

when two objects w/ different temperatures are brought together:

thermal energy passes form waker to cooler object until the two are the same temperature

16

heat

thermal energy in transfer from one body of matter to another

17

calorie (cal)

unit of heat; amount of heat it takes to raise the temperature of 1 g of water by 1 C.

18

kilocalorie (kcal)

1k calories; quantity of heat required to raise temperature of 1 kg of water by 1 C

19

joule (J)

0.239 cal; 4.184 J = 1 cal

20

specific heat

amount of heat the trust be absorbed/lost for 1 g of that substance to change its temperature by 1 C

21

water's specific heat

1 cal/g x C

22

Why is water's specific heat so high?

hydrogen bonds must be broken 1st before water molecules can begin moving faster

23

Why is water's specific heat so important?

large body of water can absorb/store huge amount of heat while warming only a few degrees
at night/winter, gradually cooling air can warm the air; moderates temperatures in coastal areas
stabilizes ocean temperatures, creating favorable enviro
keeps temperature fluctuations within limits that permit life

24

evaporation/vaporization

transformation from liquid to gas

25

heat of vaporization

quantity of heat a liquid must absorb for 1 g to be converted from liquid to gas

26

water's heat of vaporization and benefits

580 cal of heat needed
results from strength of hydrogen bonds
helps moderate Earth's climate (moist air forms air)
accounts for severity of steam burns

27

evaporative cooling and benefits

surface of liquid that remains behind after evaporation cools down
occurs b/c hottest molecules (greatest KE) most likely to leave as gas
contributes to stability of temperatures in lakes and ponds
provides mechanism against overheating (eg. sweating, etc)

28

Water is less dense as a solid because:

of hydrogen bonding
hydrogen bonds cause it to freeze in a crystalline lattice, keep molecules far enough apart to make ice 10% less dense than liquid water

29

Water's greatest density is at:

4 C and begins to expand as molecules move faster

30

benefits of lower density of ice

stability of enviro for life
if ice sank, all ponds, lakes, oceans freeze solid
insulates the water below
provides solid habitats

31

global warming has caused:

raise in temperature, which affects seasonal balance, causing ice to melt

32

solution

liquid that's completely homogenous and is a mix of 2+ substances

33

solvent

dissolving agent of a solution

34

solute

dissolved substance

35

aqueous solution

solute is dissolve in water (solvent)

36

hydration shell

sphere of water molecules around each dissolved ion

37

Water is a versatile solvent because:

it's polar

38

Water can dissolve:

ionic compounds, nonionic polar molecules, proteins

39

hydrophilic

water loving

40

Can molecules be hydrophilic and not dissolve?

Yes (eg. cotton, which is made of cellulose; molecules are so large they don't dissolve)

41

hydrophobic

nonionic, nonpolar, don't form H bonds, repel water (eg. veggie oil)

42

molecular mass

sum of the masses of all the atoms in a molecule

43

mol

exact number of objects; 6.022 x 10^23 (aka Avogadro's number)

44

A mol of one substance has:

exactly the same number of molecules as a mol of any other substance
(eg. if substance A has 342 daltons and substance B has 10 daltons, then 342 g of A will have same # of molecules as 10 g of B)

45

molarity

number of moles of solute per liter of solution

46

Mars is known for:

having ice under its surface, water vapor exists in the atmosphere and forms frost

47

__ and ___ conditions affect living conditions.

acidic, basic

48

hydrogen ion

(H+) transferred between 2 water molecules

49

hydroxide ion

water molecule that's lost a proton (OH-), neg charge

50

hydronium ion

water molecule w/ additional proton (H3O+)

51

Can H+ exist on its own?

No

52

At the equilibrium point of the hydrogen reaction:

the concentration of water molecules greatly exceeds the concentrations of H+ and OH-

53

OH- and H+ are:

very reactive

54

changes in OH- and H+ concentrations:

can affect a cell's proteins and other complex molecules

55

acid

substance that increases the hydrogen ion concentration of a solution (eg. HCl)
removes hydroxide ions b/c of tendency for H+ to combine with OH-, forming water

56

base

reduces the hydrogen ion concentration of a solution (eg. NH3)
accept hydrogen ions or disassociate to form hydroxide ions (combine w/ hydrogen ions to form water)
increases OH- concentration, but also reduces H+ concentration by formation of water

57

neutral solution

OH and H concentrations are equal

58

weak acids and strong bases

disassociate completely when mixed with water, as single arrows

59

weak acids

acids that reversible release and accept back hydrogen ions (eg. carbonic acid)

60

product of [H+][OH-]

10^-14, in any aqueous solution at 25C

61

pH

negative log of the hydrogen ion concentration
pH = -log[H+]
pH declines as H+ concentration increases
pH less than 7= acidic; pH more than 7 = basic, pH = 7 is neutral
each pH unit represents tenfold difference in H+ and OH- concentrations

62

Does a slight change in pH have any affect on living cells?

Yes; b/c chem processes of cell are very sensitive to concentrations of hydrogen and hydroxide ions

63

buffer

substance that minimizes changes in concentrations of H+ and OH- in a solution
does so by accepting hydrogen ions from the solution when they're in excess and donating hydrogen ions when they've been depleted
most solutions contain weak acid and its corresponding base, which combine reversibly w/ hydrogen ions
acid-base pairs

64

carbonic acid

H2CO3, formed when CO2 reacts w/ water in blood plasma
dissociates to yield bicarbonate ion (HCO3-) and hydrogen ion (H+)
chem equilibrium between carbonic acid and bicarbonate acts as pH regulator

65

burning of fossil fuels

adds CO2 to air, may harm marine ecosystems

66

ocean acidification

when CO2 dissolves in seawater, forms carbonic acid, lowers ocean pH
cause carbonate ion concentration decr. by 40% by 2100 --> bad c/ carbonate ions needed for calcification (build shells and corals)

67

calcification rate in a coral reef

predict that acidification will lower concent. of dissolved carbonate ions