Introduction

This is an investigation that will help you develop your understanding of osmosis and develop important experimental skills, such as obtaining, recording, and graphing results. Don’t forget to record your results in a results table with suitable headings and units placed at the top of the table.

Reading

Read page 24 and carry out the investigation following the instructions carefully.

Experimental Skills

Complete the Osmosis Practical investigating how the Concentration of Solution Affects Potato Pieces.

EXPERIMENT - Osmosis

Remember to review the Safety Guide. Complete the data table and draw a graph of your results. Answer the Conclusion and Discussion questions for this practical.

Skills

Representing osmosis data in a graph: 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 where net osmosis is zero and the water potentials are equal.

Tip: the word ‘extrapolate’ is a term used in graphing to describe the process by which the line of best fit (trend line) is extended beyond where the last point or co-ordinate has been plotted. It is in effect a way of predicting what may happen beyond the range covered by the results.

You will find that the videos in the links below help explain the investigation and how to graph your results.

Links

WATCH - Osmosis in Potato Strips - Bio Lab (YouTube)

WATCH - Osmosis - GCSE Science Required Practical (YouTube)

Review

Look at the diagrams on page 18 (Figure B2.03), page 20 (Figure B2.04) and page 21 (Figure B2.05). Refresh your memory, looking closely at the diagrams and noting the labels and the key features of each. Close the book and now try to draw and label each diagram from memory. When you have finished the first diagram, open the book, and see how much of your labelled diagram is correct, then continue for the next two diagrams, looking at the book only when you have finished drawing.

Spend a few minutes reviewing the definitions of the words in your key word file and or Quizlett App.

Make use of the activities that the Quizlett App can create.

Answer the questions on pages 27-29 and check your answers.