ANSWER SCHEME PAPER 3 MID YEAR F4 2012

ANSWER SCHEME PAPER 3 MID YEAR F4 2012

Question 1 : 1(a)(i)

ScoreExplanation

3Able to state two correct observations based on following criteria.

C1 concentration of albumen

C2 time taken

Sample Answer:(either 2):

When the percentage of concentration of albumen suspension is 10%, the time taken for enzyme reaction is 7 minutes.

When the percentage of concentration of albumen suspension is 20%, the time taken for enzyme reaction is 13 minutes.

2Able to state one correct observation and one inaccurate response.

1Able to state one correct observation or two inaccurate response or idea.

0No response or wrong response (response like hypothesis)

1(a) (ii)

ScoreExplanation

3Able to state two reasonable inferences for the observation.

Sample answer:

The rate of enzymatic reaction increases with the increase in substrate concentration.

The rate of enzymatic reaction increases with the increase in substrate concentration.

2Able to state one correct inference and one inaccurate inference.

1Able to state one correct inference or two inaccurate inference or idea.

0No response or wrong response (inference like hypothesis)

1(b)

ScoreExplanation

3

Able to record all readings of volume of urine produced

Percentage concentration of albumen suspension

Time taken/minutes

10%

7

15%

10

20%

13

2Able to record any 2 corrects

1Able to record any 1 correct

0No response or wrong response

1(c) (i)ScoreExplanation

3Able to state all the variables and the method to handle variable correctly

() for each variable and method

Manipulated Variable: Concentration of albumen suspension ()

Method to handle: Use different concentration of albumen suspension ()

Responding Variable: Time taken for the digestion of albumen ()

Method to handle: Observed and record the time taken for albumen suspension become

colorless by using stopwatch ()

Controlled variable : Enzyme concentration, temperature and pH of medium ()

Method to handle: . Fix the enzyme concentration to 1%. Use 1% pepsin, 1 ml of pepsin ()

Able to get 6 (with the correct key words)

Able to get 4 5

1Able to get 2 3

0No response or wrong response

1(c)(ii)

ScoreExplanation

3

Able to classify the apparatus and material used in the experiment

Apparatus

Materials

Syringe

Albumen suspension

Stopwatch

Pepsin

Thermometer

Water bath

Able to classify all the apparatus and material correctly.

2Able to classify two apparatus and one material correctly.

1Able to classify one apparatus and one material correctly.

0No response or wrong response

1(d)

ScoreExplanation

3Able to state the hypothesis correctly based on the following criteria:

V1 State the substrate concentration

V2 State the enzyme reaction

R - State the relationship between V1 and V2.

The rate of enzymatic reaction increases with the increase in substrate concentration

2Able to state the hypothesis but less accurate.

1Able to state the idea of the hypothesis

0No response or wrong response

1(e)(i)

ScoreExplanation

3Able to construct a table and record the result of the experiment with the following criteria:

percentage concentration of albumen suspension (%)

Time (minutes)

Rate of enzymatic reaction as percentage of albumen concentration per minute

Percentage concentration of albumen suspension (%)

Time/minutes

Rate of enzyme reaction as percentage of albumen concentration per minute

10

7

10/7

= 1.43

14

10

15/10

= 1.50

20

13

20/13

= 1.54

2Able to construct a table and record any two criteria

1Able to construct a table and record any one criteria

0No response or wrong response

1(e)(ii)

ScoreExplanation

3Able to draw a graph of rate of reaction of pepsin against the concentration of albumen suspension

P all axis with uniform scale and correct units

T all points transferred correctly

B smooth graph was plotted

2Graph with any two criteria.

1Graph with any one criteria.

0No response or wrong response.

1(e)(iii)

ScoreExplanation

3Able to explain the relationship between the concentration of albumen suspension and the rate of reaction of pepsin.

The rate of pepsin reaction increases with the percentage of the concentration of albumen suspension and it reaches a maximum value

2Able to explain briefly the relationship between the concentration of albumen suspension and the rate of reaction of pepsin.

1Able to explain the idea the relationship between the concentration of albumen suspension and the rate of reaction of pepsin.

0No response or wrong response

1(f)

ScoreExplanation

3This enzyme, which is Pepsin acts on albumen suspension to change it into clear solution. The rate of enzyme reaction increases with the substrate concentration.

1(g)

ScoreExplanation

3R. The 1 ml of enzyme used is boiled enzyme, hence it is denatured/destroyed and cannot act on the substrate.

MARKING SCHEME

QUESTION 2

1. Aim of investigating

Sample answerRemarks

Able to state the objective of investigation correctly.

Sample answer:

To study the concentration of sucrose solution which is isotonic to the cell sap of papaya slices

To determine the effect of different concentration of sucrose solution to the length of papaya slices.

Tick

2. Problem statement

ScoreExplanationRemarks

3Able to state the problem statement relating the manipulated variable with responding variable correctly.

Sample answer :

What is the concentration of sucrose solution which is isotonic to the cell sap of papaya slices?

What is the effect of difference of sucrose solution to the length of papaya slices?

One

P1- concentration of sucrose solution

P2- final length of papaya slices

2Able to state the problem statement but slightly incorrect.

Sample answer :

What is the effect of concentration of sucrose solution to the length of papaya slices?

What is the concentration of sucrose solution which is isotonic to the cell sap of papaya slices?

One

P1, H only

P2, H only

P1, P2 only

1Able to state the idea only.

Sample answer :

Sucrose solution affects the length of papaya slices.

One

P1,P2, H,

No question marks.

0No response or wrong response.

3. Hypothesis

ScoreExplanationRemarks

3Able to state the hypothesis correctly by relating the two variables correctly.

Sample answer :

When the sucrose solution is isotonic to the cell sap of plant cells, there is no net gain in size.

The higher the concentration of sucrose solution, the lesser the final length of papaya slices.

One

Must have P1, P2 and H

2Able to state the hypothesis but slightly incorrect.

Sample answer :

The isotonic solution has no effect on the plant cell sap on the length of papaya slices.

The different of concentration of sucrose solution influence the final length of papaya slices

One

P1, P2

P1, H

P2, H

1Able to state the idea only.

Sample answer :

The concentration of sucrose solution affect the plant cell sap

One

0No response or wrong response.

4. Variables

Sample answerRemarks

Able to state ALL three variables correctly.

Manipulated: Concentration of sucrose solution

Responding: Final length of the papaya slices

Fixed

: Initial length of the papaya slices

One

5. List of materials and apparatus

ScoreExplanationRemarks

3Able to state all the materials and apparatus correctly.

Sample answer :

Materials : papaya , distilled water, filter paper and

sucrose solutions with different

concentrations

Apparatus: Test tubes/ petri dishes, knife, forceps, ruler and cork borer.

One

2Able to state 3 materials and 3 apparatus.

1Able to state 2 materials and 2 apparatus.

0No response or wrong response.

6. Technique

Sample answerRemarks

Measuring the lengths of papaya slices with a ruler and recordBonus 1 mark

One

7. Procedure

ScoreExplanationRemarks

3Able to list down the complete procedures based on the following five criteria, K1, K2, K3, K4 and K5.

K1 : Procedures of assembling the materials and apparatus.

(Step 1 5)

K2 : Method to operate manipulated variable.

(Step 3)

K3 : Method to determine responding variable.

(Step 6)

K4 : Method of controlling variable.

(Step 3, 4 & 6)

K5 : Method to take precaution steps.

(Step 6)

Sample answer :

1. Seven test tubes are labelled as A, B, C, D, E, F and G.

2. Test tube A is filled with 25ml of distilled water.

3. Each test tube is filled with 25 ml of different solutions as shown as below :

Test tube B : 0.1M sucrose solution

Test tube C : 0.2M sucrose solution

Test tube D : 0.3M sucrose solution

Test tube E : 0.4M sucrose solution

Test tube F : 0.5M sucrose solution

Test tube G : 0.6M sucrose solution

4. A cork borer is used to bore 21 papaya slices. Each slice is cut to a length of 5 cm.

5. Three slice are placed in each test tube and left for an hour.

6. After an hour, the slice are removed. The papaya slices are wiped dry and the length of each slice is measured. The measurements are recorded.

7. A graph of the change in length of the papaya slices against the concentrations of sucrose solution is plotted.

One

2Able to state 3 to 4 criteria.

1Able to state at least 2 criteria.

0No response or wrong response.

8. Presentation of data / result

Concentration of sucrose solution (M)

Initial length (cm)

Final length (cm)

Change in length (cm)

1

2

3

Mean

1

2

3

Mean

0 (Distilled water)

0.1

0.2

0.3

0.4

0.5

0.6

Able to construct a table based on the following criteria.

concentration of sucrose solution

The initial and final length of papaya slices

The change in the length of papaya slices

Predicted graph

Graph of change in length of papaya slices against concentration of sucrose solution

Two

Bonus 1 mark

9. Conclusion

Sample answerRemarks

State the hypothesis.

Hypothesis accepted

One

Aspect 3 : Planning

7 9 = 3 marks

4 6 = 2 marks

1 3 = 1 marks

Summary

Problem statement

= 3 marks

Hypothesis

= 3 marks

Materials & apparatus

= 3 marks

Procedures

= 3 marks

Planning

= 3 marks

Bonus

= 2 marks

Total

= 17 marks

Change in length (cm)

Concentration of

sucrose solution (M)

0.1 0.2 0.3 0.4 0.5 0.6

0