Water

Question 1

How long did life evolve in water before spreading to land

Answer 1

3 billion years

Question 2

What does hydrogen bonding organise water into

Answer 2

a higher level of structural order

Question 3

water is “held together” by hydrogen bonds

Answer 3

Cohesion

Question 4

What does cohesion allow water to do

Answer 4

travel up plants against gravity

Question 5

How does water travel up plants

Answer 5

. Water evaporation from the leaf surface results in a tugging effect, like a chain, due to hydrogen bonding between water molecules

Question 6

Hydrogen bonding to cell molecules

Answer 6

Adhesion

Question 7

How does hydrogen bonding allow creatures to “walk on water”

Answer 7

Surface tension due to hydrogen bonding
between water molecules at the interface
between air and water

Question 8

How does water moderate air temperature

Answer 8

absorbing heat from warm air and releasing stored heat to cooler air

Question 9

Kinetic energy associated with the movement of atoms and molecules

Answer 9

Thermal energy

Question 10

Calorie

Answer 10

Thermal energy transfer from one body to another is called HEAT measured as a CALORIE – the amount of heat it takes to raise the temperature of 1 g of water by 1°C

Question 11

Thermal energy flow

Answer 11

region of higher temperature to region of lower temperature

Question 12

High specific heat

Answer 12

can absorb higher levels off heat relative to most other substances

Question 13

What does water having a high specific heat mean

Answer 13

it will change its temperature LESS than other liquids when it absorbs or loses a given amount of heat

Question 14

Why is waters high specific heat important to life

Answer 14

The water that covers most of the Earth keeps temperature fluctuations on land and in water within limits that permit life,
Living organisms are made primarily of water so they are better able to resist changes in their own temperature

Question 15

Why does water have a high specific heat

Answer 15

hydrogen bonding, extra heat has to be absorbed to break hydrogen bonds or heat is
released when hydrogen bonds form

Question 16

Heat of vaporisation

Answer 16

is the amount of heat a liquid must absorb for 1 g to be converted into a gas (water is high due to hydrogen bonding)

Question 17

Why is a high heat of vaporisation important to moderation of climate

Answer 17

Huge amount of solar
heat absorbed by tropical seas is consumed by evaporation.
The moist air then travels polewards, cools and releases
heat as it condenses forming RAIN.

Question 18

Why is a high heat of vaporisation important to stability of temperature in lakes and ponds

Answer 18

Evaporative cooling of water contributes to the stability
of temperature in lakes and ponds allowing life to
flourish.

Question 19

Why is a high heat of vaporisation important to terrestrial organisms

Answer 19

Prevents terrestrial organisms from overheating eg. evaporation of sweat from human skin; evaporation of water from plant leaves.

Question 20

Why is liquid water more dense than ice

Answer 20

As the temperature of water drops from 4°C to 0°C more of its molecules are moving too slowly to break hydrogen bonds.
At 0°C the molecules are locked in crystalline lattice each water molecule H-bonded to 4 others.
This creates uniform ‘spaces’ between the water molecules making ice less dense than water = FLOATS

Question 21

Why is ice floating important to life

Answer 21

If ice sank then eventually all ponds, lakes and oceans would freeze. Life on Earth as we know it would be impossible. In summer only the surface would thaw. Now, when an ocean cools in winter the floating ice INSULATES the liquid water below preventing it from freezing and allowing life to exist underneath eg. krill.

Solid habitat for many forms of life.

Question 22

Hydration shell

Answer 22

The sphere of water molecules around each dissolved ion

Question 23

Why is water the “solvent of life”

Answer 23

Polar compounds and ions are dissolved in biological fluids eg. blood, sap in plants and the cytoplasm of cells.

Question 24

Concentration of H+ in pure water

Answer 24

10-7 M (one ten-millionth of a mole of hydrogen ions per L of water)

Question 25

Constant product of H+ and OH-

Answer 25

10-14

Question 26

Ocean acidification

Answer 26

25% of CO2 is absorbed by the oceans which reactis with water to forn carbonic acid. this dissociates into H+ & HCO3 and the H+ combines with carbonate ions forming more HCO3

Question 27

Effects of ocean acidification

Answer 27

Less CO32- is available for calcification – the formation of calcium carbonate – by marine organisms eg. coral, shellfish. Prediction that the carbonate concentration could decrease by 40% by 2100