2.2 Water

Question 1

What is water made up of?

Answer 1

two hydrogen atoms covalently bonded to an oxygen atom (molecular formula = H2O)

Question 2

Why is water described as polar?

Answer 2

it has a slight charge difference across the different poles of the molecule
- the oxygen atom is slightly negative (δ–) while the hydrogen atoms are slightly positive (δ+)

Question 3

Hydrogen bonding

Answer 3

when a δ+ hydrogen atom is attracted to a δ– fluorine, oxygen or nitrogen atom of another molecule, it forms a hydrogen bond

Question 4

What are some properties of water?

Answer 4

cohesive property
adhesive property
thermal property
solvent proverty

Question 5

Cohesive property

Answer 5

water molecules stick to each other, due to hydrogen bonding

Question 6

Cohesive property application

Answer 6

transportation of water in plants - water is sucked through xylem vessels at low pressure

Question 7

Adhesive property

Answer 7

water will form intermolecular associations with polar and charged molecules

Question 8

Adhesive property application

Answer 8

in leaves, water adheres to cellulose molecules in cell walls to prevent evaporation

Question 9

Thermal property

Answer 9

high specific heat capacity - hydrogen bonding restrict motion of water molecules and so a lot of energy is needed to break the bonds
high latent heat of vaporisation - a lot of heat is needed for a molecule to become a vapour molecule
high boiling point

Question 10

Thermal property application

Answer 10

the evaporation of water as sweat is a fundamental mechanism employed by humans as a means of cooling down

Question 11

Solvent property

Answer 11

the polar nature of water molecule means that it forms shells around charged and polar molecules preventing them from clumping together and keeping them in solution

Question 12

Solvent property application

Answer 12

water soluble substances will usually be able to travel freely in the blood plasma, whereas water insoluble substances cannot

Question 13

What is the importance of the density of water?

Answer 13

water is less dense as a solid than as a liquid, so ice can float on water - prevent oceans from freezing, and acts as habitats for many species

Question 14

What is the importance of the transparency of water?

Answer 14

aquatic plants can undergo photosynthesis

Question 15

What processes does the water cycle include?

Answer 15

evaporation
transpiration
condensation
precipitation
infiltration
runoff
subsurface flow

Question 16

What is the importance of solubility in water?

Answer 16

transport of sodium chloride, amino acids, glucose, oxygen, fats molecules and cholesterol in blood