Question

Know what is moving and which direction it is moving in the pink cube/vinegar experiment. Describe if this is osmosis or diffusion.

Answer 1

• Diffusion can be demonstrated in agar cubes using with pH indicator and soaking treated cubes in vinegar .
• All cells require the transport of materials across the plasma membrane into and out of the cell.
• As an acid, vinegar has a large number of hydrogen ions.
• This hydrogen ions of vinegar diffuse fully into the cube.
• Remove cube from vinegar and place them on white paper
• When the hydrogen ions come into contact with the pH indicator, the solution changes colour from pink to colourless.
• Calculate volume of cube which is occupied by vinegar .

Here hydrogen ions in vinegar is moving towards the cube from high gradient to low gradient .

Diffusion

• Diffusion occurs when molecules in an area of higher concentration move to an area of lower concentration.
• As hydrogen ions from the vinegar move into the agar cube, the color of the cube changes allowing us how far they have diffused.
• Random molecular motion will cause individual molecules and ions to continue moving back and forth between the cube and the vinegar solution
• The overall concentrations will remain in equilibrium