Ch 10 Section 5

Question 1

water is the most abundant

Answer 1

liquid

Question 2

oceans, rivers, and lakes cover about

Answer 2

75% of earth’s surface

Question 3

water is an essential component of all organisms: 70% to 90% of the mass of living things is

Answer 3

water

Question 4

the chemical reactions of most life processes takes place in water, and water is frequently a

Answer 4

reactant or product in such reactions

Question 5

water molecules consist of two atoms of hydrogen and one atom of

Answer 5

oxygen united by polar-covalent bonds

Question 6

water molecule shape:

Answer 6

bent

Question 7

the angle between the two hydrogen-oxygen bonds is about

Answer 7

105 degrees

Question 8

this is close to the angle expected for … of the oxygen-atom orbitals

Answer 8

sp3 hybridization

Question 9

the molecules in solid/ liquid wate rare linked by

Answer 9

hydrogen bonding

Question 10

the number of linked molecules decreases with increasing temperature because increases in kinetic energy make

Answer 10

hydrogen bond formation difficult

Question 11

nevertheless, there are usually from … to … molecules per…

Answer 11

4 to 8; group in liquid water

Question 12

if it were not for these molecular groups, water would be a

Answer 12

gas at room temperature

Question 13

nonpolar molecules, such as methane, that are similar in size and mass to water molecules do not

Answer 13

undergo hydrogen bonding. they are gases at room temp

Question 14

ice consists of water molecules in the

Answer 14

hexagonal arrangement

Question 15

the empty spaces between molecules in this pattern account for the relatively

Answer 15

low density of ice

Question 16

as ice is heated, the increased energy of the molecules causes them to

Answer 16

move and vibrate more vigorously

Question 17

when the melting pt is reached, the energy of the molecules is so great that the

Answer 17

rigid open structure of the ice crystals breaks down, and ice turns into liquid water

Question 18

hydrogen bonds between molecules of liquid water at 0 degrees celsius are …. and more …. than those between molecules of ice at the

Answer 18

fewer; disordered; same temperature

Question 19

because the rigid open structure of ice has broken down, water molecules can

Answer 19

crowd closer together

Question 20

liquid water is

Answer 20

denser than ice

Question 21

as the liquid water is warmed from 0 degrees celsius, the water molecules

Answer 21

crowd still closer together

Question 22

water molecules are as tightly packed as possible at

Answer 22

3.98 degrees celsius

Question 23

at temperatures above 3.98 degrees celsius, the increasing kinetic energy of the water molecules causes them to

Answer 23

overcome molecular attractions

Question 24

the molecules move farther apart as the temperature continues to

Answer 24

rise

Question 25

as the temperature approaches the boiling point, groups of liquid water molecules absorb enough energy to

Answer 25

break up into separate molecules

Question 26

because of hydrogen bonding between water molecules, a high kinetic energy is needed, causing water’s boiling point to be

Answer 26

relatively high (100 degrees celsius) compared to other liquids that have similar molar masses

Question 27

at room temperature, pure liquid water is

Answer 27

transparent, odorless, tasteless, and almost colorless

Question 28

any observable odor or tase is caused by

Answer 28

impurities, such as dissolved minerals, liquids, or gases

Question 29

water freezes and ice melts at

Answer 29

0 degrees celsius at a pressure of 1 atm

Question 30

molar enthalpy of fusion of ice is

Answer 30

6.009 kJ/mol

Question 31

the molar enthalpy of fusion of ice is relatively larged compared with the molar enthalpy of fusion of

Answer 31

other solids

Question 32

water has the unusual property of …. in volume as it freezes, because its molecules form an..

Answer 32

expanding; open rigid structure

Question 33

ice at 0 degrees celsius has a density of only about …. wile liquid water at 0 degrees celsius has a density of

Answer 33

.917 g/ cm3 ; .99984 g/ cm3

Question 34

this lower density explains why ice floats in

Answer 34

liquid water

Question 35

the insulating effect of floating ice is particularly important int he case of

Answer 35

large bodies of water

Question 36

iv ice were more dense than liquid water, it would sink to the bottom of

Answer 36

lakes and ponds, where it would be less likely to melt completely

Question 37

the water of such bodies of water in temperature climates would eventually

Answer 37

freeze solid, killing nearly all the living things in it

Question 38

at 100 degrees celsius (boiling point at 1 atm) water’s molar enthalpy of vaporization is

Answer 38

40.79 kJ/ mol

Question 39

both the boiling pt and the molar enthalpy of vaporization of water are quite high compared with those of

Answer 39

nonpolar substances of comparable molecular mass, such as methane

Question 40

the values are high because of the strong hydrogen bonding that must be overcome for

Answer 40

boiling to occur

Question 41

the high molar enthalpy of vaporization makes water useful for

Answer 41

household steam-heating systems

Question 42

the steam (vaporized water) stores a great deal of

Answer 42

energy as heat

Question 43

when steam condenses in radiators, great quantities of

Answer 43

energy are released