2.2 : Water

Question 1

what effect does the uneven distribution of charges in a water molecule cause?

Answer 1

water is a polar (hydrophilic) –> so there is an unequal distribution of charges –> oxygen is more electronegative and has a higher attractive force to electrons than hydrogen –> meaning electrons are pulled towards the oxygen.

Question 2

where are the hydrogen bonds formed?

Answer 2

the positively charged hydrogen atom of one molecule are attracted to negatively charged oxygen atom of a near-by water molecule –> bind by hydrogen bonds.

Question 3

what is dipolarity of water and what does this allow the molecule to form?

Answer 3

• dipolarity : dipolarity of a water molecule enables it to form polar associations with other charged molecules (polar or ionic)
• allows it to form polar associations with other charged molecules.

Question 4

what are the thermal, cohesive/adhesive, solvent properties of water?

Answer 4

• thermal : water absorbs heat before changing state (involved breaking of hydrogen bonds)
• cohesive /adhesive : water binds to other molecules (cohesion) and charged substances (adhesion)
• solvent : water dissolves polar & ionic substances (by forming polar associations –> causing materials to draw apart)

Question 5

what is cohesion?

Answer 5

ability of like molecules to bind together.

Question 6

what is adhesion?

Answer 6

ability of dissimilar molecules to bind together / force by which individual molecules bind to surrounding materials and surfaces.

Question 7

how are metabolites transported in the blood?

glucose, amino acids, cholesterol, fats, oxygen, sodium chloride

Answer 7

• glucose : highly soluble - dissolves in blood plasma.
• amino acids : soluble in water - dissolves in blood plasma.
• cholesterol : insoluble (hydrophobic - lipid) –> transported in particles –> low-density lipoproteins (bad) & high-density lipoproteins (good)
• fats (lipids) : insoluble –> absorbed into gut (into lacteals) as droplets –> emulsified by bile salts –> transported around body (water soluble phospholipids)
• oxygen : low solubility in plasma –> combines with haemoglobin in red blood cells.
• sodium chloride : highly soluble –> transported as sodium and chloride ions dissolved in plasma.

Question 8

how can we access water when there is a lack of water supply?

Answer 8

Desalination process –> removes dissolved salts from sea / brackish (has more salinity than fresh but less than sea water) water