water
Sugar solution
water
water
water Flaccid
Aim
The aim of this Coursework is to investigate and find about how the concentration of solutions affects the role of osmosis. For this I am going to carry out experiments using different concentrations of solutions.
In this experiment we placed pieces of potatoes which had the same mass (3.7g) in water and in different concentrations of sugar solution (5,10,15,20,25%). We measured the mass of the potatoes at the beginning and at the end of the experiment, and then recorded our results.
Prediction
I will use my scientific knowledge and some of the information I got from the encyclopaedia and Internet to help me with my prediction. I predict that as the concentration of the sugar solution increases, the percentage change of the mass decreases until it becomes lower than its starting mass.
First, when I place the piece of potato in the pure water, the potatoes’ change in mass will be relatively highest therefore the water molecules will defuse into the potato because the potato has a lower concentration. When I place it in the 5% concentration sugar solution, the potatoes’ change in mass will be lower than before because fewer molecules defuse into the potato. When I place it in the 10% concentration, the change in mass will be even lower, because even lesser water molecules will go through the potato. At 15 and 20% concentration, the change in mass will go lower. In the 25% concentration, the mass of the potato will decrease than its’ starting mass, the change in mass will be negative. This is because there is a higher concentration in the potato than in the solution, so the water defuses out from the potato to the solution.
Placed in weighed Placed in
pure water potato chip sugar solution
Water enters by osmosis. Water leaves by osmosis.
Weighs more after removal. Weighs less after removal.
This is what I predict my table and graph would look like.
Fair Test
By keeping our experiment fair there would be accurate results afterwards, and we would be able to make a firm conclusion, and we wouldn’t have to keep repeating the experiment over and over again. For a fair test, we placed pieces of the potatoes which all had the same mass (3.7g) in different concentrations of solution. We used the same amounts of solution per test tube (6cm). We also repeated the experiment three times so we are sure to get accurate and fair results.
Equipment
- 6 test tubes
- 18 pieces of potato (3.7g each)
- 2 beakers
- pure water
- 5%,10%,15%,20%,25% concentration of sugar solutions
- scalpel
- a pair of tweezers
- 1 tray
Method
For this experiment, we used 18 pieces of potato which had the same mass and placed them in different concentration of sugar solutions. We put 3 pieces of potatoes in each test tube. Each piece of potato weighed at 3.7g. Each test tube was 6 cm long and had a different concentrations of solution. We put three pieces of potatoes in water first, then another15 pieces in 5%, 10%, 15%, 20% and 25% concentration of sugar solution.
We then made a table and recorded in our start mass. We left our experiments in the classroom and came back to them the next day. We took out our pieces of potatoes from the solutions and the water, and weighed them. We recorded the end mass in the table, we wrote the change between the start mass and the end mass (e.g. 3.7−3.2=−0.5), and calculated the percentage of change in mass (e.g. -0.5÷3.7×100).
Results of experiment:.
Here are the formulae I used :
Change in mass = start mass − end mass
% change = change in mass ×100
start mass
I made another table and added the three % changes of each concentration and divided them by 3 to get the average % in change in mass of the potato.
Average table
Observation and analysis
This graph has a negative correlation. From looking at the graph, I can see that as the concentration increases, the change in mass decreases until it goes under its’ starting mass. That is because water diffuses from a region of relatively high concentration to one of lower concentration for example. When the concentration was 10%, the change in mass was 12%. When it was in 15% concentration, the change in mass was 10%.
In the water the mass change is relatively highest. Pure water passes into solutions where the water is less concentrated. The water in the potato was less concentrated, so the water diffused into the potato, which made the potatoes mass increase.
In the 5% and 10% concentration, the mass of the potato increased but not as much as in the water. That is because water is more concentrated than this solution and less water molecules diffused into the potato than before.
When the concentration was 20%, the mass of the potato went down. That is because in the potato the water is more concentrated than in the 20% concentration, so water molecules moved out from the potato to where the water is less concentrated.
In the 25% concentration, the mass of the potato also went down but, at higher rate than in the 20% concentration. That is because more water molecules diffused out of the potato into the solution.
Commenting on previous prediction:
The prediction that I have made earlier in this coursework is all true, the evidence supports it. My prediction was accurate and thoughtful because I have used secondary information about osmosis from libraries and the PC.
I predicted that as the concentration of the sugar solution increases, the percentage change of the mass decreases until it becomes lower than its starting mass.
Conclusion
I found, according the evidence and by the use of potatoes in different concentration solutions, as the concentration increases, the change in mass decreases until it goes under its’ starting mass. That is because water diffuses from a region of relatively high concentration to one of lower concentration.
In the water the mass change was the highest. The water in the potato was less concentrated, so the water diffused into the potato, which made the potatoes mass increase.
In the 5% and 10% concentration, the mass of the potato increased but not as much as in the water. That is because water is more concentrated than this solution and less water molecules diffused into the potato than before.
In the 20% concentration, the mass of the potato went down. That is because in the potato the water is more concentrated than in the 20% concentration, so water molecules moved out from the potato to where the water is less concentrated. This is why the potato lost its’ mass.
In the 25% concentration, the mass of the potato also went down but, at higher rate than in the 20% concentration. That is because more water molecules diffused out of the potato into the solution where the water is less concentrated.
Evaluation
The aim of this Coursework was to investigate and find about how the concentration of solutions affects the role of osmosis. I succeeded in finding and proving out that as the concentration of a solution is increased, the change in mass decreases until it goes under its’ initial mass. It was a fair test because we placed pieces of the potatoes which all had the same mass (3.7g) in different concentrations of solution. We used the same amounts of solution per test tube (6cm). We also repeated the experiment three times so we are sure to get accurate and fair results, and we succeeded in doing that. We got very reliable results which helped me to come op with a firm conclusion. In this example below, as the concentration gets higher, the change in mass decreases. There was not any anomalous results.
Example:-
There are few things I could have done to improve the reliability of this investigation. We could’ve been more accurate in obtaining evidence i.e. use cleaner equipment free of contamination, more time to carry out the experiments as this will give us more reliable results. To improve my certainty of the conclusion, we could’ve experimented with wider range of concentrations of solutions i.e. 30%, 35%, 40%, and we could have used different masses of potatoes, and used different solutions to be experimented with i.e. alkaline or acidic solution to observe how the process of osmosis is altered. We can also experiment with different temperature, for instance -2, 0, 4, 7, 15, 25, 35 or 50 centigrade; or maybe use another substance instead of potato, such as a human cell, porous rock or a small balloon filled with lactose solution. I think using any of these the effect on osmosis will be the same as when using a potato. This is because water always diffuses from where it’s high to where it’s low in concentration. I think that my results were good enough to make an analysis because you can see from this investigation that I came up with a firm good conclusion.
Osmosis Coursework
Yazan Qabba’ah
10.8
