Diffusion And Osmosis Experiments

Question 1

What can phenolphthalein be used to investigate

Answer 1

Diffusion in agar jelly

Question 2

How would you perform an experiment to investigate diffusion in agar jelly

Answer 2

• Make up some jelly with phenolphthalein and dilute sodium hydroxide
• The jelly will be pink
• Fill a beaker with dilute hydrochloric acid
• Using a scalpel, cut out a few jelly cubes and put them in the beaker
• If you leave the cubes they’ll turn colourless as the acid diffuses into the agar jelly and neutralises the sodium hydroxide

Question 3

How can you investigate the rate off diffusion using agar jelly

Answer 3

Use different sized cubes of agar jelly and time how long it takes for each cube to go colourless. The cube with the largest surface are all volume ratio will lose its colour quickest

Question 4

How can you investigate osmosis in living systems

Answer 4

• cut up a potato into identical cylinders and get beakers with different sugar solutions in
• one should be pure water, another should be a very concentrated sugar solution, and a few in between
• measure the length of each cylinder and leave them in the beakers for about 30 mins
• take them out and measure their lengths again
• if the cylinders have drawn in water by osmosis they will be longer
• If water has been drawn out they will be shorter

Question 5

What variable do you change when investigating osmosis in living systems

Answer 5

The concentration of the sugar solution. Everything else (volume of solution, time the experiment runs for, etc) must be kept the same

Question 6

How do you investigate osmosis in non living systems

Answer 6

• tie a piece of wire around one end of some Visking tubing and put a glass tube in the other end
• pour some sugar solution down the glass tube into the Visking tubing
• put the Visking tubing in a Beaker of pure water
• measure where the sugar solution comes up to the glass tube
• leave the tubing overnight
• then measure where the liquid is in the glass tube
• water should be drawn into the Visking tubing by osmosis and this will force liquid up the glass tube

Question 7

What is phenolphthalein

Answer 7

A pH indicator. It’s pink in alkaline solutions and colourless in acidic solutions