Water and the Fitness of the Environment

Question 1

How many percent does water make up in cells
?

Answer 1

70-95%

Question 2

What is the function of the polarity of water?

Answer 2

• allows them to form hydrogen bonds with each other
• contributes to the various properties water exhibits

Question 3

What are the properties of water?

Answer 3

• cohesive behaviour
• ability to moderate temperature
• expansion upon freezing
• versatility as a solvent

-> all contribute to earth’s suitability as an environment of life

Question 5

What is surface tension?

Answer 5

measure of how difficult it is to stretch or break the surface of a liquid

Question 6

What is adhesion?

Answer 6

the attraction between different substances’ the clinging of one substance to another

Question 7

What are the functions of cohesion and adhesion in plants?

Answer 7

• 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)

Question 8

Surface tension and water

Answer 8

• 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

Question 9

Water transport in plants

Answer 9

• 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

Question 10

What is the moderation of temperature of water?

Answer 10

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)

Question 11

What is kinetic energy?

Answer 11

= energy of motion

• atoms / molecules are constantly moving -> have kinetic energy
• the faster the movement, the more kinetic energy

Question 12

What is the difference between Heat and Temperature?

Answer 12

Heat: total Kinetic energy
Temperature: average kinetic energy

Question 13

What is thermal energy?

Answer 13

kinetic energy associated with random motion of atoms or molecules

Question 14

What is heat?

Answer 14

= 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

Question 15

What is temperature?

Answer 15

• measures the intensity of heat in degrees, reflecting the average kinetic energy of molecules (regardless of volume )
• Celsius scale: measure of temperature in °C

Question 16

What are the different units of heat?

Answer 16

• 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

Question 17

What is the specific heat of a substance ?

Answer 17

= 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

Question 18

What is the water’s specific heat?

Answer 18

• 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

Question 19

Where can the specific heat of water be useful in nature?

Answer 19

oceans can moderate coastal climates
- the relatively cool ocean reduces coastal air temperature by absorbing heat

Question 20

What is evaporative cooling?

Answer 20

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

Question 21

What is the function of evaporative cooling of water?

Answer 21

• 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

Question 22

Floating of ice

Answer 22

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

Question 23

Why is it important that ice floates?

Answer 23

• 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

Question 24

What is a solution?

Answer 24

a liquid that is homogeneous mixtrue of two or more substancesW

Question 25

What is a solvent?

Answer 25

the dissolving agent of a solution

Question 26

What is a solute?

Answer 26

the substance that is dissolved

Question 27

What is an aqueous solution?

Answer 27

a solution where water is the solvent

Question 28

What is a hydration shell£?

Answer 28

when an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules

• negative oxygen regions are attracted to the cations
• positive h-atoms cling to anions

Question 29

What is a colloid?

Answer 29

a stable suspension of fine particles suspended in a liquid

Question 30

what is molarity?

Answer 30

the number of moles of solute per liter in a solution

Question 31

What is an hydroxide ion ?

Answer 31

OH-
molecule that lose H+

Question 32

What is a hydronium ion?

Answer 32

H3O+
molecule that gained H+

Question 33

What is an acid?

Answer 33

any substance that increases the H+ concentration of a solution
by releasing H+ or accepting OH-

Question 34

What is a base?

Answer 34

any substance that reduces the hydrogen ion concentration of a solution
by accepting H+ or releasing OH-

Question 35

What is a buffer?

Answer 35

substances that minimize changes in the concentrations of hydroxide and hydronium ions in a solution
- consists of acid-base-pair that reversibly combine with hydrogen ions
- in the body: weak acids and base
- in blood: carbonic acid H2CO3 and bicarbonate ions HCO3-

Question 36

What is the phosphate buffer system

Answer 36

• internal fluid of cells
• dihydrogen phosphate ions H2PO4- (acid) and hydrogen phosphate ions HPO4 2- (base)

Question 37

What is Acidification of Ocean water?

Answer 37

• atmospheric CO2 from human activities and its fate in the ocean
• CO2 is the main product of fossil fuel combustion
• 25% of human generated CO2 is absorbed by the ocean
• CO2 dissolved in seawater forms carbonic acid -> ocean acidification