1.2 Properties of Water

Question 1

Describe water molecules:

Answer 1

• it is a polar molecule: there is an uneven distribution of charge
• the oxygen side is slightly negative
• the hydrogen side is slightly positive
• this makes it a dipolar molecule

Question 2

Describe hydrogen bonding in water:

Answer 2

the slightly negative oxygen attracts the slightly positive hydrogens to form hydrogen bonds

Question 3

Descibe the solvent properties of water:

Answer 3

• many substances, including ionic substances, can dissolve in water
• this is due to its dipole nature
• the postive ions are attracted to the negative O, and the negative ions are attracted to the postive Hs
• this means the ions are totally surrounded by water molecules - they are hydrated

Question 4

Why are the solvent properties of water important?

Answer 4

• many biological reactions take place in solution
• dissolved substances can be transported around the body through blood

Question 5

What are the cohesive properties of water? Why are they important?

Answer 5

• there is cohesion between water molecules because there dipole nature means they are attracted to one another
• this helps water flow, making it good for transporting substances

Question 6

Describe the importance of water’s high specific heat capacity:

Answer 6

• water has a high specific heat capacity
• this is because a large amount of energy is required to break the relatively strong hydrogen bonds
• this means that water warms and cools down slowly
• this allows organisms to maintain a stable temperature
• this also allows aquatic organisms to live in a stable environment

Question 7

What is specific heat capacity (in terms of water)?

Answer 7

the amount of energy in joules required to raise the temperature of 1g or 1cm3 of water by 1°C