1.6.3 The Properties of Water

Question 1

Although water as a whole is electrically neutral the sharing of the electrons is

Answer 1

uneven between the oxygen and hydrogen atoms

Question 2

The oxygen atom attracts the electrons more strongly than the hydrogen atoms, resulting in

Answer 2

a weak negatively charged region on the oxygen atom (δ-) and a weak positively charged region on the hydrogen atoms(δ+), this also results in the asymmetrical shape

Question 3

This separation of charge due to the electrons in the covalent bonds being unevenly shared is called

Answer 3

a dipole

Question 4

This separation of charge due to the electrons in the covalent bonds being unevenly shared is called a dipole, when

Answer 4

a molecule has one end that is negatively charged and one end that is positively charged it is also a polar molecule

Question 5

Water is a what molecule

Answer 5

polar

Question 6

The covalent bonds of water make it a polar molecule

Answer 6

Question 7

Hydrogen bonds form between

Answer 7

water molecules

Question 8

As a result of the polarity of water

Answer 8

hydrogen bonds form between the positive and negatively charged regions of adjacent water molecules

Question 9

ydrogen bonds are weak, when there are few, so they are constantly breaking and reforming, however when there are large numbers present they form a

Answer 9

strong structure

Question 10

Hydrogen bonds contribute to the many properties water molecules have that make them so important to living organisms (6)

Answer 10

• an excellent solvent – many substances can dissolve in water
• a relatively high specific heat capacity
• a relatively high latent heat of vaporisation
• water is less dense when a solid
• water has high surface tension and cohesion
• it acts as a reagent

Question 11

The polarity of water molecules allows hydrogen bonds to form between adjacent water molecules

Answer 11

Question 12

Water has many essential roles in living organisms due to its properties:

Answer 12

• the polarity of water molecules
• the presence and number of hydrogen bonds between water molecules

Question 13

As water is a polar molecule many ions (e.g. sodium chloride) and covalently bonded polar substances (e.g. glucose) will

Answer 13

dissolve in it

Question 14

covalently bonded polar substances (e.g. glucose) will dissolve water, this allows

Answer 14

chemical reactions to occur within cells (as the dissolved solutes are more chemically reactive when they are free to move about)

Question 15

covalently bonded polar substances (e.g. glucose) will dissolve water so, metabolites can be

Answer 15

transported efficiently (except non-polar molecules which are hydrophobic)

Question 16

Due to its polarity water is considered a universal solvent

Answer 16

Question 17

The specific heat capacity of a substance is

Answer 17

the amount of thermal energy required to raise the temperature of 1kg of that substance by 1°C

Question 18

Specific heat capacity is a measure of

Answer 18

the energy required to raise the temperature of 1 kg of a substance by 1oC

Question 19

Water has a high specific heat capacity of

Answer 19

4200 J / Kg oC meaning a relatively large amount of energy is required to raise its temperature

Question 20

The high specific heat capacity is due to

Answer 20

the many hydrogen bonds present in water (it takes a lot of thermal energy to break these bonds and a lot of energy to build them, thus the temperature of water does not fluctuate greatly)

Question 21

The advantage of water shc for living organisms is that it

Answer 21

• provides suitable habitats
• is able to maintain a constant temperature as water is able to absorb a lot of heat without big temperature fluctuations
• this is vital in maintaining temperatures that are optimal for enzyme activity

Question 22

Water in blood plasma is also vital in

Answer 22

transferring heat around the body, helping to maintain a fairly constant temperature

Question 23

Water in blood plasma is also vital in transferring heat around the body, helping to maintain a fairly constant temperature, as blood passes through more active (‘warmer’) regions of the body

Answer 23

heat energy is absorbed but the temperature remains fairly constant

Question 24

Water in tissue fluid also plays an important regulatory role in

Answer 24

maintaining a constant body temperature

Question 25

In order to change state (from liquid to gas) a large amount of thermal energy must be

Answer 25

absorbed by water to break the hydrogen bonds and evaporate

Question 26

In order to change state (from liquid to gas) a large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate, this is an advantage for living organisms as

Answer 26

only a little water is required to evaporate for the organism to lose a great amount of heat

Question 27

Only a little water is required to evaporate for the organism to lose a great amount of heat, this provides a

Answer 27

cooling effect for living organisms, for example the transpiration from leaves or evaporation of water in sweat on the skin

Question 28

Properties of Water & its Role in Living Organisms Table

Answer 28

Question 29

Hydrogen bonds between water molecules allows for strong

Answer 29

cohesion between water molecules

Question 30

Cohesion between water molecules allows columns of water to

Answer 30

move through the xylem of plants and through blood vessels in animals

Question 31

Cohesion enables

Answer 31

surface tension where a body of water meets the air, these hydrogen bonds occur between the top layer of water molecules to create a sort of film on the body of water (this is what allows insects such as pond skaters to float)

Question 32

Water is also able to hydrogen bond to other molecules, such as cellulose, which is known as

Answer 32

adhesion

Question 33

Adhesion also enables water to move up the xylem due to

Answer 33

transpiration