Water and the Fitness of the Environment Flashcards
How many percent does water make up in cells
?
70-95%
What is the function of the polarity of water?
- allows them to form hydrogen bonds with each other
- contributes to the various properties water exhibits
What are the properties of water?
- cohesive behaviour
- ability to moderate temperature
- expansion upon freezing
- versatility as a solvent
-> all contribute to earth’s suitability as an environment of life
What is surface tension?
measure of how difficult it is to stretch or break the surface of a liquid
What is adhesion?
the attraction between different substances’ the clinging of one substance to another
What are the functions of cohesion and adhesion in plants?
- Cohesion helps to transport of water and dissolved nutrients against gravity in plants
- adhesion helps to counter the downward pull of gravity (eg between water and plant cell walls)
Surface tension and water
- ST is related to cohesion
- water has a greater ST than most liquids
- at the interface between water and air, there is an ordered arrangement of water molecules, H-bonded to one another and the water below
- some animals can stand on water without breaking the surface
Water transport in plants
- cohesion due to h-bonds between water molecules helps hold together the column of water within cells
- adhesion of water to the cell wall by h-bonds helps to resist the downward pull of gravity
- evaporation from the leaves pulls water upward from the roots through water-conducting cells
What is the moderation of temperature of water?
Water moderates air temperature (thermoregulatory ability)
- absorbs heat warmer from air and releases the stored heat to cooler air
- can absorb or release a large amount of heat with only a slight change in its own temperature (heat bank)
What is kinetic energy?
= energy of motion
- atoms / molecules are constantly moving -> have kinetic energy
- the faster the movement, the more kinetic energy
What is the difference between Heat and Temperature?
Heat: total Kinetic energy
Temperature: average kinetic energy
What is thermal energy?
kinetic energy associated with random motion of atoms or molecules
What is heat?
= thermal energy
- a measure of the total amount of kinetic energy due to molecular motion in a body of matter
- heat depends in part on the matter’s volume
eg swimming pool has lower temp than a pot of boiling water, but because it has a bigger volume, it has more heat (thermal energy) than the pot
What is temperature?
- measures the intensity of heat in degrees, reflecting the average kinetic energy of molecules (regardless of volume )
- Celsius scale: measure of temperature in °C
What are the different units of heat?
- calorie (cal) = the amount of heat it takes to raise the temperature of 1g of water by 1°C
(same with releasing energy to lower temp) - kilocalorie (kcal)= 1000 cal , the quantity of heat required to raise the temp of 1 kilogramm of water by 1°C
- Joule
= energy unit that equals to 0.239 cal
1 J = 0.239 cal
1 cal = 4.184 J
What is the specific heat of a substance ?
= a measure of how well a substance resists changing temperature when it absorbs or releases heat
- the amount of heat that must be absorbed/lost for 1g of that substance to change its temperature by 1°C
What is the water’s specific heat?
- 1cal/g °C
- water has a high specific heat, which allows it to resist to changes in temperature
- because of H-bonds!
heat is absorbed when hydrogen bonds break
heat is released when h bonds form
-> much of the heat water absorbs is dissipated in breaking h bonds
Where can the specific heat of water be useful in nature?
oceans can moderate coastal climates
- the relatively cool ocean reduces coastal air temperature by absorbing heat
What is evaporative cooling?
Evaporation = vaporization : the transformation of a substance from liquid to gas
- heat of vaporisation= the quantity of heat a liquid must absorb for 1g of it to be converted to gas
- water has a high heat of vaporisation (due to h bonds)
- as a liquid evaporated, the surface of the liquid that remains behind cools down -> evaporation cooling
- sweating
What is the function of evaporative cooling of water?
- helps to stabilise the temperature in organisms and bodies of water
- due to high heat of vaporisation of water
- the hottest molecules escape as gas and leave the cooler molecules behind
- water is a great coolant
- contributes to the stability of temps in lakes and ponds
- mechanisn that prevents terrestrial organisms from overheating
Floating of ice
ice is less dense than liquid water
- h bonds are more organised in solid state -> less dense than liquid
- water has greatest density at 4°C
Why is it important that ice floates?
- important for the fitness of environment
- if ice sank, then eventually all lakes and ponds would freeze killing all life form
- life can exist under the frozen surfaces
- the rate at which glaciers and arctic sea ice are disappearing poses an extreme challenge to animals that depend on ice for their survival
What is a solution?
a liquid that is homogeneous mixtrue of two or more substancesW
