Biology Coursework

Problem

A cook wishes to prepare chips for a meal the following day. How does the cook keep the chips so that they will stay fresh.

Experiment 1

Background

Potatoes have selectively permeable membranes (cell membranes ) that lets water move from cell to cell by osmosis

Plan

I am investigating what you should keep chips in to keep them fresh. I will try to keep the chips the same weight and I will put them in the same amount of liquid solution.

Hypothesis

I think the chips should be kept in pure water because if kept in salty water all the water would leave the potato so it would just be salt in it so it would rot.

Apparatus

Potato, corer, balance, scalpel, boiling tubes, water, salt solution, tile.

Method

6 chips of potato were cut about the same size and weight , 3 were put in to boiling tubes full of water and 3 were put into a boiling tube of 1 molar salt solution. They were left for a few days.

Results:

liquid Beginning weight End weight % change

Salt solution 5.6g 6.01g +43%

water 5.6g 5.4g -28%

Experiment 2

Hypothesis

Because of experiment 1's results, we decided to try solutions between water and 1 molar salt solution. We decided to have 3 test tubes of 2.5 ml water to 7.5 ml 1 molar salt solution and 3 test tubes of 7.5 ml water to 7.5 ml 1 molar salt solution

Method

We did the same as in experiment 1 but put the potato in the solutions talked about in the hypothesis.

Results:

start weight Ml of water Ml of salt sol End weight % change

2.10g 2.5 ml 7.5 ml 1.6g - 4.2

2.10g 2.5 ml 7.5 ml 1.7g - 3.7

2.10g 2.5 ml 7.5 ml 1.8g - 3.0

2.40g 7.5 ml 2.5 ml 1.8g - 4.2

2.80g 7.5 ml 2.5 ml 2.2g - 3.0

2.60g 7.5 ml 2.5 ml 1.8g - 6.2

Conclusion

Doing the...