Water Flashcards
How long did life evolve in water before spreading to land
3 billion years
What does hydrogen bonding organise water into
a higher level of structural order
water is “held together” by hydrogen bonds
Cohesion
What does cohesion allow water to do
travel up plants against gravity
How does water travel up plants
. Water evaporation from the leaf surface results in a tugging effect, like a chain, due to hydrogen bonding between water molecules
Hydrogen bonding to cell molecules
Adhesion
How does hydrogen bonding allow creatures to “walk on water”
Surface tension due to hydrogen bonding
between water molecules at the interface
between air and water
How does water moderate air temperature
absorbing heat from warm air and releasing stored heat to cooler air
Kinetic energy associated with the movement of atoms and molecules
Thermal energy
Calorie
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
Thermal energy flow
region of higher temperature to region of lower temperature
High specific heat
can absorb higher levels off heat relative to most other substances
What does water having a high specific heat mean
it will change its temperature LESS than other liquids when it absorbs or loses a given amount of heat
Why is waters high specific heat important to life
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
Why does water have a high specific heat
hydrogen bonding, extra heat has to be absorbed to break hydrogen bonds or heat is
released when hydrogen bonds form
Heat of vaporisation
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)
Why is a high heat of vaporisation important to moderation of climate
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.
Why is a high heat of vaporisation important to stability of temperature in lakes and ponds
Evaporative cooling of water contributes to the stability
of temperature in lakes and ponds allowing life to
flourish.
Why is a high heat of vaporisation important to terrestrial organisms
Prevents terrestrial organisms from overheating eg. evaporation of sweat from human skin; evaporation of water from plant leaves.
Why is liquid water more dense than ice
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
Why is ice floating important to life
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.
Hydration shell
The sphere of water molecules around each dissolved ion
Why is water the “solvent of life”
Polar compounds and ions are dissolved in biological fluids eg. blood, sap in plants and the cytoplasm of cells.
Concentration of H+ in pure water
10-7 M (one ten-millionth of a mole of hydrogen ions per L of water)
