2.4 - Water

Question 1

4 points

Water as a transport medium

Answer 1

• water can stick together (cohesion)
• water can stick to other materials (adhesion) - helps flow through organisms
• allows for transport of water through the xylem
• has a high surface tension which supports small organisms like pond skaters

Question 2

Water as a metabolite (3):

Answer 2

can be involved in many reactions like:
1. hydrolysis
2. condensation
3. photosynthesis

Question 3

environment for organisms, property of water and what benefit is there?

Water as a habitat

Answer 3

• provides a stable environment for organisms, resists sudden temperature changes
• water freezes to form ice - bonds are held further away, makes it less dense than water
• insulates the layer and organisms below can move and survive

Question 4

Water as a cooling mechanism

Answer 4

• a lot of energy is required to evaporate water
• organisms can use this as a method of cooling without using too much water - takes energy away from the surface

Question 5

Water as a buffer

Answer 5

• has a high specific heat capacity
• contains a lot of hydrogen bonds between water molecules so a lot of energy is absorbed before breaking
• resists to rapid changes in temperature

Question 6

Water as a solvent

Answer 6

• water is polar so negative oxygens are attracted to the positive ions - slightly positive hydrogens are attracted to the negative ions
• each ion is surrounded by water molecules and the compound dissolves

Question 7

Roles of water (6):

Answer 7

1. solvent - many substances dissolve in water
2. temperature control - can buffer sudden changes
3. cooling mechanism through evaporation
4. habitat - survive and reproduce in water
5. metabolite - chemical reactions requiring water
6. transport - organisms use water to move substances

Question 8

How do water molecules form hydrogen bonds?

Answer 8

• each water molecule consists of a partially negative oxygen and a partially positive hydrogen end
• hydrogen attracts towards the oxygen and forms a hydrogen bond

Question 9

How is water a dipolar molecule?

Answer 9

• shared electrons pull towards the oxygen molecule - gives it a slight negative charge
• hydrogens are left with a positive charge