Water 2.2 30'

Water and its importance for living organisms 

In this section you will learn everything about the water, about its composition, polarity, hydrogen bonds and what makes water so unique in terms of its physical properties. You will also have the chance to look at how solubility of a substance determines the method of transportation in the blood. 


Key words 

Learn and test your biological vocabulary for 2.2 Water using these flashards.

Clean sweep - quick revision through the whole topic 

These slides summarise the essential understanding and skills in this topic. 
They contain short explanations in text and images - good revision for all students.

Read the slides and look up any words or details you find difficult to understand.

Video tutorial

A short video tutorial is planned here.

Revision summary list for 2.2 Water 

  • Hydrogen bonds form between polar water molecules.
  • This force give water special properties, e.g. cohesiveness, adhesiveness, thermal
    and solvent properties.
  • Glucose, amino acids and salts are hydrophilic while cholesterol and fats are hydrophobic.
  • Compare the thermal properties of water with those of methane and explain how this affects its use a as a coolant in sweat.
  • Compare the solubility of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in water and link this to the way they are transported.
  • Explain benefits of water properties to living organisms (Transparency and density not required.)
  • Evaluate how significant hydrogen bonding is in the properties of water

Revision mindmaps

These diagram summaries cover the main sections of topic 2.2 Water
Study them and draw your own list or concept map from memory.

Review questions

This is a self marking quiz containing questions covering the topic outlined above.
Try the questions to check your understanding.

1

The diagram below shows dotted lines between a group of water molecules.
What do these dotted lines represent?

Hydrogen bonds form between polar water molecules. Between the O and the H of an adjacent molecule.

2

Which properties of water molecules could be said to result from hydrogen bonding?

Hydrogen bonding gives water special properties, e.g. high cohesiveness, high adhesiveness, high specific heat capacity, and excellent solvent properties.

Transparency is a property of water, but it is not caused by hydrogen bonding.

3

Some medicines are designed to dissolve in a glass of water.

What is the term used to describe polar molecules which are easily soluble in water?

Glucose, amino acids and salts are hydrophilic while cholesterol and other fats are hydrophobic.

4

What is the difference between oxygen molecules (carried in red blood cells) and glucose molecules (carried in blood plasma) which can explain why they are transported in different ways in the blood?

Compare the high solubility of glucose, amino acids, and sodium chloride in water and link this to the way they are transported in blood. Oxygen is slightly soluble in water.
Compare the low solubility fats in water an link this to the fact they are not transported in blood very well.

5

Which properety of water helps to keep lakes at relatively stable temperatures?

Explain benefits of water properties to living organisms (Transparency and density not required.)

Because water has a high specific heat capacity, it takes a lot of energy to make it change temperatue, and this is what cools the skin in sweating.

6

The diagram below shows some molecules of water, methane and oxygen.

For what reason are the boiling points of methane and oxygen so much lower than the boiling point of water?

Hydrogen bonding is really important in the properties of water. By holding the water molecules together more strongly the hydrogen bonds cause water to have a higher m.p. and b.p than methand. C-H bonds in methane (CH4) are evenly aranged around the molecule so it is not polar so there is no hydrogen bonding in methane, and also in oxygen, the O-O bond is not polar.

7

Which of the following moleculels are readily soluble in water?

Water has important solvent properties.
Polar molecules and ionic salts dissolve readily in water and this helps them to be transported in the blood.

Total Score:

Revision fun for the Water topic.

Everyone needs a bit of fun while they revise. Try this Water topic wordshoot revision game.
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