How is osmosis affected by the concentration of salt that we use?

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Biology Coursework

Introduction

We are carrying out an investigation to see how the concentration of water will affect osmosis within a potato core. We were given a choice whether to decrease the water concentration with a salt or sugar solution, we thought; it was easier to work with salt solution though as the sugar solution became sticky when we decreased the water solution. I will use two sets of results to see how an increase in salt solution affects osmosis.

Strategy

We will use potatoes to show that osmosis is occurring, we have to use the same potatoes as water density’s may change as will other things if you vary between potatoes, we will place a 4cm long core of potato (from the same potato) into different concentration of salt in water. Before the potato is placed in the solution, the weight and length will be recorded. It is highly important that we use the same length potato as the surface area would affect the osmosis. This is important as it increases the reliability and accuracy as the only variable is still the salt concentration. We will have 6 different measurements of salt concentration, In Ml: 0 salt/ 100 DW, 20 salt/ 80DW, 40 salt/ 80 DW, 60 salt/ 40 DW, 80 Salt/ 20 DW and 100 salt/ 0 DW, we will make the solution of salt and water in 100ml but after it is mixed some will be poured out as a test tube is not large enough, this will not affect our results as the concentration and ratio or the salt solution will not change. After the potato has been placed in the solution it will be left for 24 hours as osmosis takes at least 30 minutes to show results, after we have left our potato we will remove it and record the length and weight. If osmosis has occurred then a change in size and weight should occur. However if the water concentration is greater inside the potato core then it will get smaller. We will record our results in a table to show the percentage change. This experiment will be repeated twice to ensure accuracy.

Preliminary

We have got relatively good results, for example the potato cores that had 0% concentration of salt around them were meant to get bigger and the potato cores with 100% salt around them were meant to get smaller which did happen. We did encounter some problems with doing this experiment which meant it was not easy to carry out and we found out that getting one core of potato and chopping it into three took up too much space in a potato and was hard to find a potato big enough. , originally we were going to measure ...