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Required Practical: Osmosis
Osmosis is a process where water moves across a PARTIALLY PERMEABLE MEMBRANE from an area of HIGH WATER CONCENTRATION to an area of LOWER WATER CONCENTRATION. It’s a key concept in cell biology that can be investigated through a practical experiment using potato cylinders in sugar solutions.
The Osmosis Experiment Setup
Preparing Your Samples:
- Begin by CUTTING POTATO CYLINDERS of the same size.
- Immerse the cylinders in DIFFERENT SUGAR SOLUTIONS with varying concentrations (e.g., 0.2 mol/dm³, 0.4 mol/dm³, etc.) to see how different solute concentrations affect osmosis.
- One cylinder should be placed in PURE WATER as a CONTROL.
Measuring Mass Changes:
- Using a MASS BALANCE, record the initial mass of the potato cylinders and then place them in the beaker of solution
- After around 24hrs, take the cylinders out, blot them with a PAPER TOWEL to remove surface moisture and REWEIGH to determine mass change.
Analysing Results:
- If cylinders in sugar solutions GAIN mass, water has moved INTO the cells by osmosis, indicating the solutions had a HIGHER WATER CONCENTRATION than the inside of the potato.
- If cylinders in sugar solutions LOSE mass, water has moved OUT OF the cells by osmosis, indicating the solutions had a LOWER WATER CONCENTRATION than the inside of the potato.
- If cylinders in sugar solutions stay the SAME mass, water has neither moved out, nor moved into the cells, this is because the solutions had the SAME WATER CONCENTRATION as the inside of the potato.
Variables:
- The CONTROLLED VARIABLES in this experiment include, the volume of the solution, temperature, time, and type of sugar/salt. These should be kept the SAME across all samples to ensure a fair test.
- The DEPENDENT VARIABLE is the MASS of the potato cylinders, and the INDEPENDENT VARIABLE is the sugar solution CONCENTRATION.
Calculating Results:
- The effect of the sugar solution on osmosis can be quantified by calculating the PERCENTAGE CHANGE in mass for each sugar concentration.
Minimising Errors:
- Ensure the potato cylinders are FULLY SUBMERGED in the solutions without touching the sides of the beaker.
- FULLY DRY the potato cylinders before measuring their mass
- REPEAT the experiment multiple times to calculate a MEAN PERCENTAGE CHANGE, reducing random errors.
Required Practical: Osmosis
Osmosis is a process where water moves across a PARTIALLY PERMEABLE MEMBRANE from an area of HIGH WATER CONCENTRATION to an area of LOWER WATER CONCENTRATION. It’s a key concept in cell biology that can be investigated through a practical experiment using potato cylinders in sugar solutions.
The Osmosis Experiment Setup
Preparing Your Samples:
- Begin by CUTTING POTATO CYLINDERS of the same size.
- Immerse the cylinders in DIFFERENT SUGAR SOLUTIONS with varying concentrations (e.g., 0.2 mol/dm³, 0.4 mol/dm³, etc.) to see how different solute concentrations affect osmosis.
- One cylinder should be placed in PURE WATER as a CONTROL.
Measuring Mass Changes:
- Using a MASS BALANCE, record the initial mass of the potato cylinders and then place them in the beaker of solution
- After around 24hrs, take the cylinders out, blot them with a PAPER TOWEL to remove surface moisture and REWEIGH to determine mass change.
Analysing Results:
- If cylinders in sugar solutions GAIN mass, water has moved INTO the cells by osmosis, indicating the solutions had a HIGHER WATER CONCENTRATION than the inside of the potato.
- If cylinders in sugar solutions LOSE mass, water has moved OUT OF the cells by osmosis, indicating the solutions had a LOWER WATER CONCENTRATION than the inside of the potato.
- If cylinders in sugar solutions stay the SAME mass, water has neither moved out, nor moved into the cells, this is because the solutions had the SAME WATER CONCENTRATION as the inside of the potato.
Variables:
- The CONTROLLED VARIABLES in this experiment include, the volume of the solution, temperature, time, and type of sugar/salt. These should be kept the SAME across all samples to ensure a fair test.
- The DEPENDENT VARIABLE is the MASS of the potato cylinders, and the INDEPENDENT VARIABLE is the sugar solution CONCENTRATION.
Calculating Results:
- The effect of the sugar solution on osmosis can be quantified by calculating the PERCENTAGE CHANGE in mass for each sugar concentration.
Minimising Errors:
- Ensure the potato cylinders are FULLY SUBMERGED in the solutions without touching the sides of the beaker.
- FULLY DRY the potato cylinders before measuring their mass
- REPEAT the experiment multiple times to calculate a MEAN PERCENTAGE CHANGE, reducing random errors.
