Osmosis Investigation

Osmosis Investigation

Introduction

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Mr. and Mrs. Brown own a fish and chip shop; they employ Lee for an

hour after school every day to prepare the chips, which are to be

fried during the evening. Lee peels the potatoes, cuts them into chips

and then places them in containers of salty water to prevent them from

drying up. There have been complaints that the chips are sometimes

soft and limp. Mr. Brown wants to sack Lee who he considers to be

slapdash and careless, but Mrs. Brown argues that sometimes the chips

are perfectly satisfactory so it can't be anything to do with Lee. She

also points out that when Lee is unable to work and his friend James

(a much more dependable character) stands in for him, the chips are

equally variable.

Preliminary Experiment

As evidence

Label 3 specimen tubes A B and C. Add your name to all 3. Using a

measuring cylinder, pour 20cm3 of water in tube A and 10cm3 in tube B.

Similarly, pour 20cm3 of 17% sucrose solution in tube C and 10cm3 in

tube B. Working on a white tile, cut 6 cylinders of potato tissue out

of a large potato using a cork borer. Work in the same direction. Cut

all 6 to exactly the same length, eg 50mm, 60mm etc. Trim the ends at

90 degrees. Place 2 cylinders into each specimen tube. Leave the

potato cylinders for 24 hours. Then using forceps, remove the

cylinders from the specimen tubes, dry on a paper towel and measure.

Note the new lengths and also note whether the tissue is firm or

flabby. Record results.

I will be using this preliminary experiment as a guide line to the

actual experiment.

Equipment required

Ø 10 specimen tubes - 5 for first experiment and 5 for the repeat

Ø Measuring cylinder - 25ml3

Ø Salt solution - 1M

Ø White tile or dissecting board

Ø 1 potato - 6 cylinders of potatoes cut from it (2 potatoes just in