Session Two (1.2.2.): Osmosis

 Introduction

The next area to focus on is osmosis. Define osmosis and make sure that you understand that it is only related to water. It is essential that you refer to water potential, rather than to the importance of osmosis to living organisms, particularly in relation to plants.

You may be asked to apply the above knowledge to unfamiliar situations in exam questions. Remember to always state the direction of water movement in relation to water potential.

Reading

Read through and make notes on pages 20-24 of your coursebook.

 Links

Now work through the following resources:

WATCH – Transport in Cells: Diffusion and Osmosis (YouTube) Links to an external site. – you have watched this previously, but you may wish to review it.

WATCH – Osmosis (Twig) [Not available with sample course]

EXPLORE – Osmosis and Volume (Twig) - there are some very useful resources here, including experiments and videos. [Not available with sample course]

WATCH – Osmosis (YouTube) Links to an external site.

Experiment

Complete the Osmosis Practical: Download Osmosis Practical:

‘Investigating How the Concentration of Solution Affects Potato Pieces’. Remember to review the Safety Guide Download Safety Guide

first. Complete the data table and draw a graph of your results. What conclusions can you make about the potato's water potential from your graph?

Skills

You need to be able to graph data from osmosis experiments. These graphs are always line graphs. They have both positive and negative values. When drawing your line, ensure that you do not extrapolate beyond the plots. The value where the line intersects the axis is the value when net osmosis is zero and the water potentials are equal.

Activity

Answer the questions on pages 21 and 23.

Review

Complete the Questions on Osmosis on pages 27-29. Check your answers.