Sample answer Q1 (Paper 3)

Question 1 (Paper 3)

Observation
In 0.2M of sucrose solution, the final diameter of potato disc is 1.90 cm.
In 0.6M of sucrose solution, the final diameter of potato disc is 1.40 cm.
Your answer must be specific. Where do u get it?? From the title in the given table.

Inference
(At 0.2M of sucrose solution) water molecule diffuses into the potato disc by osmosis.
(At 0.6M of sucrose solution) water molecule diffuses out of the potato disc by osmosis.
You give reason based on your observation. But remember, inference 1 for observation 1 and inference 2 for observation 2. Jgn. silap, rugi....

Variables
Manipulated variable
Concentration of sucrose solution : Use five different concentrations of sucrose solutions

Responding variable
Final diameter of the potato disc : Record the final diameter of potato disc by using metre rule
The word record and the instrument used are important.
//
Percentage change in diameter of potato disc : Calculate the percentage change in diameter of potato disc   
                                                                       by using the formula :
                                (Final – Initial) diameter of potato disc x 100%
                                          Initial diameter of potato disc
If you choose to write about the formula, must state clearly

Constant variable
Time taken to immerse the potato discs : Fix the time (to immerse the potato discs) at 20 minutes.
If the exact time or units are stated in the question, students must write them down. If not, telor ayam...

Hypothesis
As the concentration of sucrose solution increases, the final diameter of potato disc / the percentage change in diameter decreases.
Just the MV + RV and the relationship(higher, lower); no need to explain further.
Majority of the students like to write `depends on', `affects', `influences'....only 1 mark for this..rugi lo...

Table
1. Title and units (must be correct)
No units will be given in the question. Students must refer the earlier page.
2. Apply readings from the table given earlier.(salin jer)
3. Some calculation.

Graph
1. Both axes with correct units and title
2. All points plotted correctly (don't simply add any readings on you own; eg. connect it to 0 ka...)
3. Smooth curve touching all points.

Relationship
The concentration of sucrose solution which is isotonic to the cell sap of potato disc is *0.49M. The percentage change in diameter is zero because
the rate of water that diffuses in and out of the cell is equal.
Must explain.

Prediction
Diameter (of potato disc) is more than 1.9 cm
Distilled water is hypotonic to the cell sap of potato disc
so more water diffuses into the potato (disc) by osmosis.
We predict more or less by referring to the data from the earlier page. Don't simply guess.

Operational definition (Give explanation based on the experiment; not theoretically)
Osmosis is the movement of water to / from potato disc through the plasma membrane (of potato) due to the difference concentration between sucrose solution and cell sap of potato cell that will result in changes / decrease / increase in diameter of potato disc.

We don't write osmosis is the movement of water molecules from the region of `high water concentration/low solute concentration' to the region of `low water concentration/high solute concentration' through the semi permeable membrane....as in the book (theory)

Classifying
Salin balik je...dlm kotak....kacang

Total : 33 marks