[2.4] water

Question 1

what makes water a polar molecule?

Answer 1

• shared postive hydrogen atoms are pulled towards the negative oxygen atom
• the other side of each hydrogen atom is left with a slightly positive charge
• the oxygen atom is left with a slightly negative charge

Question 2

what gives water its properties that makes it vital for living organisms?

Answer 2

• hydrogen bonding gives water some of its useful properties
• hydrogen bond is the attraction between the slightly negatively charged oxygen atoms and the slightly positively charged hydrogen atoms of other water molecules

Question 3

what are the 5 most important properties of water?

Answer 3

1. metabolite
2. good solvent
3. large latent heat of vaporisation
4. high specific heat capacity
5. cohesion

Question 4

what are some other important properties of water? [4]

Answer 4

• it is transparent
• extremely high surface tension
• high adhesive properties
• density

Question 5

what is the importance of water being a metabolite?

Answer 5

water is involved in many reactions, such as photosynthesis, hydrolysis and condensation reactions

Question 6

what makes water a good solvent?

Answer 6

• the fact that water is polar makes it a good solvent
• the slight positive charge on hydrogen atoms will attract any negative ions in the solute
• the slight negative charge on the oxygen atoms of water will attract any positive ions in the solute

Question 7

what is the importance of water being a good solvent?

Answer 7

• many essential polar substances can dissolve in water
• allows them to be transported easily around animals and plants, in blood or xylem, to cells where they are needed

Question 8

what does (water) having a large latent heat of vaporisation mean?

Answer 8

• this means a lot of energy is required to convert water in its liquid state to a gaseous state
• this is due to the hydrogen bonds
• a lot of energy is needed to break the hydrogen bonds between water molecules to turn it into a gas

Question 9

what is the importance of water having a large latent heat of vaporisation for humans?

Answer 9

• this means that water provides a significant cooling effect
• when humans sweat they release water onto their skin
• large amounts of heat energy from the skin is transferred to the water to evaporate it, and therefore removing a lot of heat and cooling the organism

Question 10

what does (water) having a high specific heat capacity mean?

Answer 10

• this means a lot of energy is required to raise the temperature of water
• this is because some of the heat energy is used to break the hydrogen bonds between the water molecules

Question 11

what is the importance of water having a high specific heat capacity?

Answer 11

• this means the temperature of water remains relatively stable, even if the surrounding temperature fluctuates significantly
  > internal temperatures of plants and animals should remain relatively constant despite the outside temperature due to the fact that a large proportion of the organism is water
• enzymes do not denature
• provides a stable environment for aquatic organisms

Question 12

what is the importance of water being cohesive?

Answer 12

• due to water molecules sticking together, when water moves up the xylem in plants due to transpiration it is a continuous column of water
  > easier to draw up a column rather than individual molecules
• provides surface tension to water
  > enables small invertebrates to move and live on the surface, providing them with a habitat away from predators within water

Question 13

what is cohesion?

Answer 13

the tendency for water molecules to stick together (due to hydrogen bonding)

Question 14

what is adhesion?

Answer 14

the tendency for water to stick to other things