Lab 3: Diffusion and Osmosis 

Materials

• Part I: Brownian Movement
• Suspended charcoal solution/India ink particles to represent large molecules 
• Part II: Diffusion of Molecules in Various States
• Perfume 
• Timer for measuring how many seconds it takes for perfume to travel
• Ruler for measuring how far perfume travels in feet
• Agar plate for boring holes
• Agar
• IKI for agar plate
• Methylene blue for agar plate
• Part IIIA: Role of Membranes in Diffusion
• Thistle tube apparatus for observing diffusion
• Different concentrations of water using salt 
• Dialysis tubes
• Part IIIB: Effects of Temperature on Diffusion
• Dialysis tubes 
• Hot water bath
• Cold water bath 
• Bags 
• Pen for labeling
• Weight measurer 

Exercises

• Part I: Brownian Movement
• Discuss questions such as:
• "Are molecules constantly moving?"
• "How can we determine whether they are moving or staying still?"
• Use suspended charcoal solution to represent large molecules 
• Observe movement of molecules under microscope
• Part II: Diffusion of Molecules in Various States
• Observe diffusion of gas within a gas
• Measure (in seconds) how long it takes perfume to travel in the atmosphere of the room (in feet)
• Calculate to mph
• Test how long it takes for observer to smell perfume from across the room
• Observe diffusion of a liquid in a solid
• Put two holes in agar plate
• Drop IKI in one hole, and Methylene blue into the other 
• Let liquids dissolve into agar until end of lab period
• Compare distances traveled into agar by each liquid 
• Part IIIA: Role of Membranes in Diffusion
• Subject living cells to different concentrations of water
• Examine the results not he turgor pressure inside the cell
• Part IIIB: Effects of Temperature on Diffusion
• Set up dialysis tubes in hot water and cold water bath at each table 
• Label