Osmosis Concept 1. Water molecules are always moving about 2. Net movement of WATER MOLECULES (Solvent) from a solution of [higher] of water to one with [lower] of water 3. Movement of WATER MOLCULES must be through a PARTIALLY PERMEABLE MEMBRANE
Water Potential ‘High’ Water Potential Instead of using the word concentration for water… We use WATER POTENTIAL - Water potential is the measure of tendency for water to move from one place to another - Water moves from High Water Potential to Low Water Potential ‘Low’ Water Potential
Osmosis Concept (revised) 1. Net movement of WATER MOLECULES (Solvent) from a solution of higher concentration of water to one with lower concentration of water 2. Movement of WATER MOLCULES must be through a PARITALLY PERMEABLE MEMBRANE water potential water potential
Container A (Concentrated Solute Solution) 20% Water Concentration 80% Solute Concentration Container B (Diluted Solute Solution) 66.6% Water Concentration 33.33% Solute Concentration Remember Diffusion? Net Movement of particles down a concentration gradient from an area of higher concentration to an area of lower concentration! Legend Water molecule Partially Permeable Membrane Solute molecule
It’s about the Word Play A B 80% sucrose 20% water 20% sucrose 80% water Net Concentrated Solution (Sucrose for example) Low Water Potential Low concentration of Solvent High concentration of Solute Hypertonic compared to B Dilute Solution High Water Potential High Concentration of Solvent Low Concentration of Solute Hypotonic compared to A
POE Spot the errors! Semi-Permeable Membrane A 10% sucrose solution B 20% sucrose solution “Osmosis taking place via the uni-direction movement of water molecules from A to B” Solution A is hypertonic solution Solution B is hypotonic solution
Spot the errors! Semi-Permeable Membrane A 10% sucrose solution “Osmosis taking place via the uni-direction movement of water molecules from A to B” A 10% sucrose solution B 20% sucrose solution Solution A is hypertonic Solution B is hypotonic V V
Misconceptions 1. Semi-permeable membrane (Partially) 2. This is a hypertonic solution (need to be relative to something) 3. Molecules only move from high water potential to low water potential (It’s the net movement, molecules do not stop moving anyway)
TECHNIQUE TO OVERCOME MISCONCEPTION(DEMONSTRATION)
2 20 drops of vanilla
QUESTION: Will you be able to smell the vanilla that is inside the balloon? Why or why not? PURPOSE:
Can the students apply the concept of permeability?
Dostudents believe that a balloon can be semi-permeable?
Do they believethat its semi-permeability will allow them to smell the vanilla through the balloon?
QUESTION: If freshener is sprayed in the front of the classroom, will the students in the back be able to smell it? PURPOSE:
Do the students believe that molecules are constantly in motion?
Do students believe that molecules want to spread out?
Are students aware of the movement of molecules from a high to low concentration?
Tick ( / ) for the picture related to osmosis process and tick ( X ) for the picture related to diffusion process. Tick ( / ) for the picture related to osmosis process and tick ( X ) for the picture related to diffusion process Picture quiz
ATP ENERGY Water ATP energy Gas Molecules Ink drop in solution Blood cell Isotonic drink Colour gas Liquid molecules Grape jus Fish in hypotonic
Movement of substance Tonicity Movement of molecules Semi-permeable membrane Syrup drink SEMI-PERMEABLE MEMBRANE Perfume No semi-permeable membrane Solid molecules