Investigate plant tissue in different solution concentrations
Plan a fair concentration comparison and describe changes in mass and firmness.
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall cell membranes and osmosis.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
In a solution-concentration investigation, what should be varied?
What you will learn
- Plan a fair concentration comparison and describe changes in mass and firmness.
- Apply the idea to a supplied biological example or investigation.
Set up a matched comparison
Comparable pieces of plant tissue, such as potato cylinders, can be immersed in a range of known solution concentrations. Concentration is the independent variable; mass change over a fixed interval is a possible dependent variable. Use tissue from a comparable source with matched starting dimensions, temperature, solution volume and immersion time.
Measure initial and final mass using the same balance and consistent gentle blotting. Repeat each concentration. Percentage change makes comparisons between slightly different initial masses more useful, but it does not remove every difference in tissue condition or surface exposure.
Describe before explaining
In a simple model with retained solute, more dilute surroundings may produce water entry, mass gain and greater firmness. More concentrated surroundings may cause water loss, mass loss and reduced firmness. Describe the supplied observations first, then explain them using osmosis.
Plant tissue is made of many cells, and a tissue-level measurement does not directly show every membrane or the condition of every cell. Extended learners use water potential and cell-state terminology in later lessons. These plans and sample results remain preparation for supervised practical work.
Sources for this lesson
Pause and explain
What does a tissue mass loss show directly?
Worked example
A plant cylinder is 4.0 g initially and 4.4 g after immersion. Describe the mass change.
Show the worked solution
- Subtract initial from final.
- 4.4 − 4.0 = 0.4 g.
- The positive change is a gain; water entry is a possible explanation under the model.
Answer A 0.4 g mass gain.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A cylinder changes from 3.5 g to 3.15 g. Describe its mass change.
Give me a hint
Final minus initial.
Compare my reasoning
- 3.15 − 3.5 = −0.35 g.
- It lost mass.
A 0.35 g loss.
Look for these in your work
- Give magnitude and sign.
Name three controls when comparing concentrations.
Give me a hint
Keep tissue and exposure conditions comparable.
Compare my reasoning
- Match tissue source and dimensions.
- Use the same immersion time and temperature.
Any three of tissue source/dimensions, time, temperature, solution volume and blotting method.
Look for these in your work
- Choose controlled variables, not concentration.
Why is using one damaged cylinder only in the strongest solution a problem?
Give me a hint
Consider another cause of water or mass loss.
Compare my reasoning
- Damage may alter membranes or cause leakage.
- Use comparable undamaged tissue and repeats.
Tissue damage confounds concentration; use matched tissue and repeats.
Look for these in your work
- Identify the confound.
Common mistakes
- Describe observations separately from inferred mechanism.
- Percentage adjustment does not replace experimental controls.
What can you explain now?
What does a tissue mass loss show directly?
Compare with the explanation
The measured tissue became lighter.
Net water loss is an interpretation using the stated conditions.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Write a fair plant-tissue concentration comparison.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.