The concentration of the sap inside potato cells.

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Michael McMillan

0.O

Science Investigation (biology 1)

Introduction

We are doing a science investigation on finding out the concentration of the sap inside potato cells.

Variables

* The weight of the potato piece

* The size of the potato piece

* The concentration of the sugar solution after

* The room temperature

The variable that I am testing is the concentration of the potato piece, before and after the experiment.

Pre-test

I decided to do a pre-test so I could get an idea on what concentrations I could use for the investigation. I did one concentration, which was 0.75 molars. This concentration turned out to be far too high.

When I did the pre-test I cut a piece of potato with a cork borer and then cut them into three slices each at 1cm long. We decided on three slices so we could have a more accurate result. I then weighed each piece and they all weighed 0.30grams. I recorded my results

I accurately measured the concentration of the sugar solution, which was 0.75 molars. I got the concentration by putting 15mls of sugar solution and 5mls of water this made it so that there was 75% sugar solution in the beaker, which is 0.75 molars. I placed the three potato slices into the solution and left it over night. The next day I weighed it and I found that each slice had gained weight. They each weighed 0.39 grams. I then recorded my results and the differences between the starting weight and the finishing weight. The result increased far too much so I decided that I didn't need the sugar solution to be so high. To improve my pre-test I could have done another concentration, high was

Prediction

I predict at 0.10molars it will increase weight more than all the others where as 0.50molars I think will decrease the most. I think it will stay the same about 0.20-0.30molars because they are the two concentrations that aren't too high or too low. 0.50 is far too high and I know that it will decrease weight far too much.

I think the potato slice will be firmer because the water in the beaker surrounding the potato slice will pass through the cells. The cell wall is freely permeable and will allow most molecules to pass through it. The semi-permeable membrane has pores, which are big enough to let most particles through for instance water particles. When the water particles go into the cell it will make it heavier and will weigh more.
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Scientific reason for my prediction

In nature water concentrations will always try and balance by osmosis. This is how a plants roots absorb water from the soil. The root cells have a higher concentration than the damp soil, so the water is drawn in.

In my experiment the potato has a low water concentration and therefore it will draw water out of the weaker sugar solutions. It will also lose water to the stronger sugar solutions. The movement of water to or from the potato will stop when the water concentrations have equalised.

Plan
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