Practical: Investigating the Rate of Diffusion

Question 1

Investigating the rate of diffusion using visking tubing

Answer 1

Visking tubing is a non-living partially permeable membrane made from cellulose

Small pores, prevent starch and sucrose from leaving but allow smaller molecules like glucose in by DIFFUSION.

Add starch and glucose to visking tubing and place in a test tube, use benedicts test for glucose and iodine test for starch.

The aim is to see what substances have diffused out and what haven’t.

Question 2

Investigating how SA:V Ratio affects the rate of diffusion using agar

Answer 2

• Agar cubes
• Time diffusion of ions through different sized cubes
• Cubes placed in boiling tube containing HCL

Either measure :
- Time taken for acid to COMPLETELTY change colour of indicator in agar blocks
- Distance travelled into block by acid (shown by change in colour by indicator) in a GIVEN TIME PERIOD

Plot graph for both