Osmosis Investigation coursework

• Use more mixes of solution in between the range I already have.

• Use bigger chips to see whether it will affect how
• Leave the chip in for a longer period of time to give a wider range of results.
• Record results to 2 decimal places in order to give more accurate results

 All in order to give me a more detailed view of osmosis.

Main Experiment

Prediction

 My prediction is that chips placed in the listed solutions above 0 molar concentration will either keep the same mass or lose some.

Equipment used

• Potatoes – to cut the chips from
• 100 ml beakers – to hold the solutions
• Measuring cylinder – to accurately measure the amount of solution poured into beaker
• Pipette – to add or take away from the measuring cylinder
• 3 sets of different coloured straws – to show which potato is which, as there are 3 chips in each beaker.
• Core borer – to cut all the chips to same size, width, length, etc.
• Scales – to accurately measure each chip to 2 decimal places.
• Stopwatch – to measure the length of time the chip is in the solution

 Method

 For the main experiment I chose to change/add a couple things. The first being to leave all my chips in for an hour. The second thing being to use molar solutions of: 0, 0.2, 0.4, 0.6, 0.8 and 1. (I have shown how I made them in a table below.) To start the experiment, firstly I cut the potato chips to a standard size width and length with the core borer. I then weighed them. The mass of each chip was approximately 1.3 grams, but they did vary. I then mixed together my solutions so the total volume was 50 millilitres. I did this because it was easier to work out the values of the different molar solutions I had to mix together. I then put my chips in the beakers. When the 60 minutes was up, I took the chips straight out of the solution, dabbed the excess water off with a paper towel, and weighed them again recording my results as I weighed each one.

 Concentration Table

 

To make my experiment fair, I need to control the variables listed so they are constant. If they were not, it would mess up my results and lots of outliers would become apparent.

 Variables to be changed

• The concentration of the solution – To make this accurate I will measure the quantity of each solution I need with a measuring cylinder.

 

 Variables to be controlled

• Temperature – To keep this the same I will left each beaker in the same room and placed them all in the same part of the room. e.g. not selected chips in front of a window or in the shade.
• Surface area of the chip – to keep this the same, I used the core borer to cut out the chips.
• Time chip is submerged in solution – To keep this the same I timed the experiment with a stopwatch until the 60 minutes was up.
• Agitation of chip – To keep this under control I watched my beakers at all times, making sure that no one jogged them or the table.
• Scales – I zeroed the scales each time to ensure nothing affected my results.
• Type of potato – I kept this the same because other potatoes may have a different density.

 

Table of results

Test 1

Test 2

Test 3

Averages

 

Analysis of results

 When looking at the results, there is a definite pattern occurring. They show that when the potato is in a 0 molar solution, the mass is increasing. But even at 0.2, the mass is already decreasing. The pattern continues with 0.4's mass decreasing even more. This shows that the potato contains less salt than the solution, so the water is being pushed from the potato to the solution because the solution is less concentrated with water particles. But some outliers did occur. This was perhaps because the surface area of the chip was wider.

 Conclusion

 In conclusion, I found that osmosis occurs the most with distilled water. I expected this because to my scientific knowledge, I already knew that the less dilute solution would travel to the more dilute solution. In this case it was the salt moving from the potato to the Distilled water. But when I tested a higher solution, 0.2 molar, it proved that the potato had less salt than the solution as it gained mass.

 Evaluation

 I think that my experiment went well and was quite accurate. If I could do it again and make it better I would do lots of things such as:

• Cut my potato chips more accurately by measuring the width of the original potato slice, making sure it was equal all round.
• Not use straws to mark the chips. Because when the straws are put in place, they are piercing the potato. Therefore it could of affected my results.
• Use more accurate scales. (One that goes to more decimal places) To make my results more accurate.
• Use more solutions. Such as 0.05, 0.1, 0.15, etc.
• Leave the potato chip in for a longer period of time.

By Frankie Baker