Active transport
There are times when the substance moves from the low concentrated region to the high concentrated region. This is called Active transport and also takes up more energy than usual diffusion.
Method of experiment
It would be more accurate to explain the apparatus and then relating to the method of the experiment, how the actual apparatus is used in the experiment.
Apparatus
- 6 potatoes
- 6 beakers
- Pure distilled water
- Metal clamp, or stand
- Pieces of string
- Potato cutter or alternatively a Stanley knife
- Weighing scale
- Measuring cylinder
- Stop watch or any other instrument to record time
- Mixing tool, such as a spatula or metal piece etc
- Sugar
- Safety specs
The experiment is to investigate in osmosis, I will be using 6 potatoes solely for the purpose of keeping the experiment more accurate, the potatoes will be placed over 6 beakers, each of these beakers shall contain a solution from a range of pure distilled water and concentrated sucrose. Each potato will be hung over its respective solution and beaker by use of a clamp and string. The mass of the potatoes shall be weighed before and after the experiment, any change in the properties shall be recorded. I will explain the aspects of fair testing later on.
The 6 beakers shall 200ml of different sucrose solutions; this variation in concentration will be achieved by adding 100ml of distilled water to each beaker, which will have varying mass of sucrose thus resulting in different concentrations for the beakers. The measuring cylinder shall be used to ensure the equality of the sugar solution in each beaker.
A small piece from each potato will be cut using the knife and hung on the string from the metal clamp and will be kept there for a certain period of time depending on the experiment. For the sake of accuracy, the experiment shall be repeated twice, the first experiment will have a time of 1 hour and the second shall be a full 24 hours.
Fair testing and variables
The whole point of scientific investigations is to receive results based on theories and hypothesises. To ensure the success of the theory of the results need to be accurate, which leads us to fair testing. The first variable in the experiment that will need to be moderated is the room temperature. As with most scientific experiments temperature can affect the experiment, therefore the temperature in this particular experiment shall be kept at a room temperature, which is about 22-23C. Variation to the sucrose concentrations is important to show the results are flexible with different circumstances. The same volume of sucrose solution will be kept (which is 100ml). The same potato type will be used, different potatoes will differ the results, as the cell properties would not be the same. The weighing scale must be the same and the potato chips should be the same mass, around 10g. The time should stick to its own criteria, either 1 hour or 24 hours. This will be recorded by use of the stopwatch.
Safety
As with all scientific experiments, safety should be well considered. The experiment should be conducted standing up with safety goggles on. This is to prevent anything going into the person’s eyes. The knife and any other sharp objects should be handled carefully.
Obtaining evidence
Here are the results from the experiments for 1 hour and 24 hours, the potatoes were placed back into their solution immediately after examination.
Results for 1 hour:
Results for 24 hours:
Calculating the average mass
To carry on the accuracy of this investigation, I will calculate the average (or mean) mass of the potatoes.
Mean= Sum of all the values / The total number of values.
Therefore:
Mass of potato 1 (10.38g) + Mass of potato 2 (10.32g) / 2 = 10.35g
Average masses for the potatoes for 1 hour:
Average masses for the potatoes for 24 hours:
Now that the average of the experiments have been calculated I can now calculate the change in mass in the potatoes after the experiment
Changes of mass for 1 hour:
Changes of mass for 24 hours:
Analysis
Here are the representation of my results in a grapical form.
Graph for 1 hour
Graph for 24 hours
Graph for Change of mass in potatoes for 1 hour
Graph for Change of mass in potatoes for 24 hours
Conclusion
In my conclusion, the potatoes with the lowest concentration gained the most mass, and would become hard relating back to the Turgor theory I stated earlier. In contrast to this, the potatoes in the most concentrated solution lost the most weight thus becoming plasmolysed and limp also relating back to the background I have mentioned earlier.
Evaluation
In general the experiment was succesful the results were consistent and also were in accordance with the theories made at the start.. The experiment could have been improved by:
- More subjects used instead of potatoes
- More potatoes
- Wider time ranger
- Different molarities
Using this variety of methods could have improved the experiemnt, however I was generally satisfied with the results of this osmosis experiement.
