✅ 3. Required Practical: Investigating The Effect Of Sugar Or Salt Solutions On Plant Tissue (B1) Flashcards
What is the Aim of this Practical
In this practical you will plan and carry out an experiment. In the experiment you will investigate how the concentration of solution surrounding plant cells affects the movement of water by osmosis into or out of the cells.
What Is Osmosis And How Can It Be Tested?
Osmosis is a special type of diffusion, where water moves across a partially permeable membrane from a dilute solution to a concentrated solution. The cytoplasm inside plant cells is a solution and the cell membrane around it is partially permeable, so osmosis occurs in plant cells.
What Health and Safety Measure are there
- Take care with sharp knives
- Clear up any spilt water to avoid any hazards
- Carefully clear and sipose of any smashed glass
Equipment List for Osmosis Required Practical
- plant tissue, e.g., potato, sweet potato, or beetroot
- range of concentrations of sugar or salt solutions
- distilled (pure) water
- apple corer
- sharp knife
- white tile
- filter paper
- tweezers
- boiling tubes
- measuring cylinder
- ruler
- balance
- stop-clock
Method for Osmosis Required Practical
- Measure the mass of two pieces of vegetable using a balance. Cut the pieces of vegetable so that they are all the same mass. Record the mass/length of the pieces of vegetable in the results table.
- Measure 15 cm^3 of distilled water using a measuring cylinder. Put the water into a boiling tube.
- Measure 15 cm^3 of one concentration of the sugary solution. Put the solution into the boiling tube.
- Put a piece of vegetable in each boiling tube and press start on the stop-watch.
- After 10 minutes, use tweezers to remove the pieces of vegetable from the boiling tubes and place on some filter paper.
- Dab the pieces of vegetable to remove any excess liquid.
- Measure the mass/length of the pieces of vegetable using a balance/ruler. Record the new mass in the results table.
Independant Variable for Osmosis Required Practical
The Independant Variable in this experiment is the range of sugar concentrations you put in each solution that you prepare to put your vegetable in. This is because this is the variable that is altered in this experiment.
Dependant Variable for Osmosis Required Practical
The Dependant Variable in this experiment is the percentage change in the length of the potato. This is because this is the variable that is being tested or measured in the experiment.
Control Variables for Osmosis Required Practical
The Control Variables are the diameter, length and size of the vegetable, the amount of liquid placed in each sample, how much liquid you dab off when measuring/weighing, and the temperature of all the solutions. These are control variables because these are the variables that are kept the same in the experiment.
How do you lay out the Results Table for the Osmosis Practical
I laid my table out in 4/5 different columns. These columns included the ‘Concentration of sugar (ml)’ on the left, then the ‘Length before (cm)’, the ‘Length after (cm)’, the ‘Percentage Change’ on the right.
How do you Lay out the Graph for the Osmosis Practical
Firstly, the graph will be one with 2 quadrants, as in some concentrations the vegetable will have came out smaller than it was when it was put in.
‘The Percentage Change(%)’ is placed on the Y-Axis, while the ‘Concentration of Sucrose (mol/dm^3)’ was put on the X-Axis.
Overall, the graoh had a negative correlation, as the higher the concentration of sucrose, the less the vegetable would increase in size and the more it would decrease in size.
Explain the Results obtained from the Experiment, with reference to Osmosis
The general trend was that the higher the concentration of sugar in the solution, the less the vegetable would grow, and the more it would shink in length. This is because in a dilute solution, the water molecules will go towards the more concentrated solution inside the potato, passing through it’s partially permeable membrane, through the process of osmosis. However in a highly concentrated solution, water molecules will travel from the more dilute potato towards the more comcentrated solution through the potato’s partially permeable membrane, by the process of osmosis.
Evaluate the Method. How acvurate do you think your results are? Why? What would you change if you did it again?
Overall, I think the method was good enough to get a general trend of how osmosis affects the length of a potato when put into different solutions. To improve the method from just measuring the length, I would measure the length as well as the mass of the potatos before and after experiment, which would’ve obtained more accurate results. The reason I say this is because there were other groups that were getting slightly different and more accurate results than what was being obtained from my one. Going on from this, I believe that change will improve the accuracy of the results, as there would be two data points to compare from, and is certainly something that would be added in tne future.
Explain how you think the surface area of the plant tissue samples might affect osmosis
The surface area of the plant tissue may affect the osmosis (or the rate of osmosis) taking place when left in test tubes of differently concentrated liquids over a day/ a few hours. This is because a higher surface area will allow for a larger partially permeable membrane, which will lead to osmosis being able to take place easier and also quicker as a result of this, leading more water molecules to enter or exit the vegetable/plant faster.
Describe And Explain for Osmosis RP
As the concentration of sucrose increases, the percentage change decreases, meaning there is a negative correlation between the two. Initially, you can see a positive percentage change, especially between 0 moles to 0.3 moles. This increase in mass takes place as water molecules pass from the dilute sugar solution to the more concentrated potato, through it’s partially permeable membrane by osmosis. Between plotted points between mass change in 0.3 and 0.4 moles, you can see that the line cuts the x-axis at approximately 0.335 moles. This means that there has been not net osmosis, however there has been movement back and forth between the solution and potato through the partially permeable membrane. As the concentration of the sugar solution increases further (to around 0.4 and 0.5 moles) the potato begins to decrease in mass, as much as -6.1% (when placed in the 0.5 mole solution of sucrose). This will be down to water travelling from the more dilute potato, through it’s partially permeable membrane to the more concentrated sugar solution, through this process of osmosis.
