Task 1 - what’s the solution? Osmosis Task 1 - what’s the solution? Can you define what each of the following are and give an example? Click on the boxes to reveal the answers. a solute a solvent a solution definition definition definition the liquid into which the solute is poured and dissolved substance that is dissolved in a solvent is made when a solute is dissolved in a solvent example e.g. salt and sucrose example e.g. water and ethanol example e.g. salty water © www.teachitscience.co.uk 2015 23698

Osmosis Task 2 – plants and water Look at the two pictures. Describe the differences. Can you explain the differences? © www.teachitscience.co.uk 2015 23698

Osmosis Task 3 – model cell experiment Instructions Make two model cells by filling two lengths of Visking tubing (tie a knot in one end) with a dilute (weak) salt solution. Put one model cell into a boiling tube containing distilled water. Put the other model cell into another boiling tube containing a concentrated (strong) salt solution. Leave for 10 minutes. dilute salt solution dilute salt solution distilled water concentrated salt solution Predict what you think will happen. After 10 minutes look at the model cells and describe their appearance. Explain what has happened and why. © www.teachitscience.co.uk 2015 23698

net movement of water molecules Osmosis Task 4 – membranes and solutions water membrane sugar solution net movement of water molecules What can you say about the movement of the water and sugar molecules in a solution? Which particles can move through the membrane and why? Will the water molecules move both ways through the membrane? Which side has the highest concentration of water molecules? What will be the overall movement of water molecules? Click on the correct arrow. © www.teachitscience.co.uk 2015 23698

partially permeable membrane Osmosis Task 5 – partially permeable membranes What does partially mean? In part, not totally, slightly etc What does permeable mean? Allows liquids or gases to pass through it What is meant by a partially permeable membrane? A membrane that lets small molecules through but not large molecules Draw a diagram to show how a partially permeable membrane would allow water molecules through but not glucose molecules. Generally, small particles can pass through… …but large particles cannot. partially permeable membrane © www.teachitscience.co.uk 2015 23698

Osmosis Task 6 – what is osmosis? Copy out and complete the definition of osmosis. Click each box to reveal the answer. Osmosis is a special type of diffusion. Osmosis is the diffusion of water molecules … … from a region of high concentration of water molecules … … to a region of low concentration of water molecules … … across a partially permeable membrane. © www.teachitscience.co.uk 2015 23698

Osmosis Task 7 – osmosis and blood cells Look at the three pictures. Describe the appearance of the red blood cells in each. What do you think has caused the differences in the cells? Make a poster to explain the role of osmosis in pictures B and C. Make sure that you include one deliberate mistake on your poster. A C B Image source: http://commons.wikimedia.org/wiki/File:Osmotic_pressure_on_blood_cells_diagram.svg © www.teachitscience.co.uk 2015 23698

Osmosis Going further sugar solution water net movement There are as many water molecules on the right as there are on the left. What will be the net movement of water molecules by osmosis? Look at the diagram to see if you can explain why. Several of the water molecules are momentarily attracted to the sugar molecules and are not free to move. © www.teachitscience.co.uk 2015 23698

Osmosis Because there are more freely moving water molecules on net movement Sugar molecules can pass through the membrane but, being surrounded by a cloud of water molecules, they move more slowly. Because there are more freely moving water molecules on the left, more diffuse through the pores of the membrane from left to right than from right to left. © www.teachitscience.co.uk 2015 23698

Osmosis Task 8 – osmosis animation Design and make your own video to explain osmosis. © www.teachitscience.co.uk 2015 23698

Osmosis Teaching notes Task 3 - model cell The model cell makes a great starting point to stimulate discussion about movement of molecules in and out of cells. Equipment needed per group: 2 x boiling tubes and stand 2 x 15 cm lengths of Visking tubing cotton thread distilled water concentrated sugar or salt solution dilute sugar or salt solution Task 7 Students are asked to leave one deliberate mistake on their poster. When completed the posters are swapped with another group. Students then try to identify mistakes on the poster. Task 8 The students will need access to tablets to be able to make a video or animation of osmosis. Modelling dough would be ideal to use. As an alternative students could write and give a short presentation to the rest of the class. © www.teachitscience.co.uk 2015 23698