1.
Osmosis in Potato Cells
Aim: To investigate how different concentrations of sucrose solution affect
the mass of potato cells due to osmosis.
Apparatus:
Potato
Cork borer / knife (to cut uniform potato pieces)
Ruler
Balance (for measuring mass)
Beakers
Different sucrose concentrations (e.g., 0.0M, 0.2M, 0.4M, 0.6M, 0.8M,
1.0M)
Distilled water
Paper towels
Method:
1. Cut equal-sized potato cylinders using a cork borer or knife.
2. Measure the initial mass and length of each potato piece.
3. Place each piece into a beaker containing a different sucrose
concentration.
4. Leave for 30-60 minutes.
5. Remove, blot dry with a paper towel, and remeasure the final mass
and length.
6. Record results and calculate percentage change in mass.
IV: Concentration of sucrose solution
DV: Change in mass (or length) of potato cylinders
CV:
Volume of sucrose solution
Size and shape of potato pieces
Duration of experiment
Temperature of surroundings
Expected Results:
Hypotonic solution (distilled water): Potato gains mass (water
enters).
Isotonic solution: No significant mass change.
Hypertonic solution (high sucrose): Potato loses mass (water
leaves).
Percentage change = ((Final mass - Initial mass) / Initial mass) × 100
2. Food Tests
General Procedure: Each test involves using specific reagents that cause a
colour change when the target nutrient is present.
Test for Starch
Reagent: Iodine solution
Method: Add iodine solution to the food sample and observe the
colour change.
Positive Result: Blue-black (starch present).
Negative Result: Yellow/brown (no starch).
IV: Presence of starch in the sample
DV: Colour change
CV:
Volume of iodine solution used
Amount of food sample tested
Test for Reducing Sugars (Benedict’s Test)
Reagent: Benedict’s solution
Method:
1. Add Benedict’s solution to the sample.
2. Heat in a water bath (~80°C) for 5 minutes.
3. Observe colour change.
Positive Result: Blue → Green → Yellow → Orange → Brick-red
(more sugar = deeper colour).
Negative Result: Remains blue (no reducing sugar).
IV: Presence of reducing sugars
DV: colour change
CV:
Volume of Benedict’s solution
Heating time and temperature
Test for Protein (Biuret Test)
Reagents: Sodium hydroxide (NaOH) + Copper sulfate (CuSO₄)
Method:
1. Add NaOH solution to the sample, then add CuSO₄ dropwise.
2. Observe colour change.
Positive Result: Purple/lilac (protein present).
Negative Result: Remains blue (no protein).
IV: Presence of protein
DV: Colour change
CV:
Volume of Biuret reagent
Amount of food sample
Test for Fat (Emulsion Test)
Reagents: Ethanol + Water
Method:
1. Add ethanol to the food sample and shake well.
2. Pour the solution into cold water.
3. Observe for a cloudy layer.
Positive Result: White emulsion (milky layer) (fat present).
Negative Result: Clear solution (no fat).
IV: Presence of fat
DV: Formation of an emulsion
CV:
Volume of ethanol and water
Shaking time
3. Enzyme Activity (Effect of Temperature on Amylase)
Aim: To investigate how temperature affects the activity of amylase in
breaking down starch.
Apparatus:
Starch solution
Amylase enzyme solution
Iodine solution
Water bath
Test tubes
Stopwatch
Pipette
Spotting tile
Method:
1. Place iodine solution drops into a spotting tile.
2. Heat starch solution and amylase to different temperatures (e.g., 10°C,
30°C, 60°C).
3. Mix starch and amylase in a test tube and start the stopwatch.
4. Every 30 seconds, take a sample and place it on iodine in the spotting
tile.
5. Observe the colour change:
o If iodine stays blue-black, starch is still present.
o If iodine turns brown/yellow, starch has been broken down by
amylase.
6. Record the time taken for starch to completely disappear at each
temperature.
IV: Temperature of the enzyme-starch mixture
DV: Time taken for starch to be completely broken down
CV:
Volume of starch and amylase solutions
Concentration of starch and amylase
Amount of iodine used
Time intervals for checking reaction
Expected Results:
Low temperature (0-10°C): Slow reaction (low enzyme activity).
Optimum temperature (~37°C): Fastest reaction, starch digested
quickly.
High temperature (>50°C): Enzyme denatures, reaction stops.
Graphs:
o Osmosis → % change in mass vs. sucrose concentration.
o Enzymes → Time for starch to disappear vs. temperature
(bell-shaped curve).
4. Photosynthesis Experiment (Effect of Light Intensity on Oxygen Production in
Pondweed)
Aim: To investigate how light intensity affects the rate of photosynthesis in pondweed by
measuring oxygen bubbles released.
Apparatus:
Pondweed (e.g., Elodea)
Beaker with sodium hydrogen carbonate solution (provides CO₂)
Lamp (light source)
Ruler
Stopwatch
Test tube or funnel + measuring cylinder (to collect oxygen)
Method:
1. Place a piece of pondweed in a beaker containing sodium hydrogen carbonate
solution (for a constant CO₂ supply).
2. Position a lamp at a set distance from the beaker.
3. Allow the pondweed to adjust for a few minutes.
4. Count the number of oxygen bubbles released per minute OR collect gas in a
measuring cylinder.
5. Repeat at different distances of the lamp (e.g., 10 cm, 20 cm, 30 cm, etc.).
6. Record results and compare the rate of photosynthesis at different light intensities.
IV: Distance of the lamp (light intensity)
DV: Number of bubbles per minute / Volume of oxygen collected
CV:
Same pondweed specimen
Same concentration of sodium hydrogen carbonate
Same temperature (use a water bath if needed)
Same lamp (constant wattage)
Same time for each reading
Expected Results:
As light intensity increases (lamp closer), more bubbles are produced (faster
photosynthesis).
At a certain point, the rate plateaus due to other limiting factors (CO₂ or
temperature).
Graph:
x-axis: Distance of lamp / Light intensity
y-axis: Number of bubbles per minute / Oxygen volume
Curve increases and then levels off when other factors become limiting.
