BIOLOGY : Mid-semester break work

SPM Biology Paper 3

Guidelines on how to answer Paper 3 questions.

The following pointers were made available by MOE to schools as SPM
examination techniques for answering Biology Paper 3 questions. Take note that it is relatively easy to score high marks in Paper 3 if you are able to follow the suggested answering techniques closely.

PAPER 3 : QUESTION 1

The following scientific skills are tested in Question 1:

1. OBSERVATION

QUESTION : State two observations….

ANSWER : Write down what can be observed only. Do not do any analysis, comparison or

conclusion. For most experiments, the observation can be written in the form:

The ….(responding variable) ….. at …..(manipulated variable)… is (state reading of measuring instrument)

( Write the observation for the highest and lowest value of the responding variable.)

2. INFERENCE

State one inference which corresponds to each observation. An inference is a brief explanation of the observation, based on scientific knowledge which you already know. 

(But in Physics, the scheme demands that inferences be written as follows: The (responding variable) is determined by/affected by/ influenced by/ controlled by/ changed by (manipulative variable).

3. MEASURING AND USING NUMBERS

Record the reading of thermometer, stopwatch, measuring tools , ruler etc. from the given diagram. Be careful of the number of decimal places which you should have in your readings.

4. COMMUNICATING

Construct the table using the given titles, record the relevant data or calculation. Units of measurements should be written together with table titles, not with readings.

5. INTERPRETING DATA

Explain / state the relationship between manipulated and responding variables as obtained from a graph of the results.

6. CONTROLLING VARIABLES

Variables (STATE)	Method to handle the variables (MUST USE VERB and state the INSTRUMENT used)
MANIPULATED	Use / ….
RESPONDING	Record / measure using …. (Observe/ read/ are not accepted)
CONTROLLED	Use the same…/ Maintain …

7. MAKING HYPHOTHESIS

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

·         State the manipulated variable

·         State the responding variable

·         Relate the manipulated variable and the responding variable (When relating mv and rv, do not use neutral relationships like ‘affects’ or ‘influence’ or ‘changes with’. Commit yourself to one of the following relationship terms: ‘increases with’ / ‘decreases with’ .

8. PREDICTING

QUESTION : If the experiment is repeated ….., predict the observation ……

ANSWER : One number or relevant statement e.g. the (responding variable) will be higher / lower than (the value in the first experiment)

9. DEFINING OPERATIONALLY

This is a definition in the context of the experiment, and not the textbook definition.

EXAMPLE 1:

An experiment is carried out to investigate photosynthesis and the number of bubbles released is counted. The operational definition of photosynthesis would then be:

Photosynthesis is the process where green plants release bubbles in the presence of light, carbon dioxide and water.

EXAMPLE 2:

An experiment is carried out to investigate photosynthesis and leaves are tested with iodine solution for the presence of starch. The operational definition of photosynthesis would be:

Photosynthesis is the process where green leaves in the presence of light, carbon dioxide and water,

produce starch which turns iodine solution dark blue.

(You must have a phrase which includes the context of the experiment / experimental conditions.)

Or even simpler:

To define operationally, say the question is asking you concerning Operational Definition of Strong Acids, and the manipulative variable is the acid with various pH value and the responding variable is The Reading of The pH meter.

Hence the operational definition is :

A strong acid causes the pH meter to show a smaller magnitude reading when the bulb of the pH meter is immersed in each of the samples of various concentrations of the acid, given that the volume of the tested acids is the same and all acids are of the same type.

(Note: The operational definition is supposed to tell a person (whom you assume does not know a single thing about the chemical principles in the first place) what to observe as the responding variable and the conditions in which the experiment is taking place (tell what is the fixed variable and the how the manipulated variable is represented)

Another example is: The elasticity of vulcanised rubber
Given the experiment is the experiment comparing the elasticity of two strips of rubber, one vulcanised, the other non-vulcanised.

Hence, the operational definition of 'the Elasticity of Rubber' is given as:
The Elasticity of Rubber is operationally defined as the "Difference between final lengths of the respective rubber strips after the weight used to stretch is removed, and their respective original lengths" given that the two rubber strips have the same initial length but are of different types of rubber, one being vulvanised rubber, the other being non-vulcanised rubber.

Another example: define operationally the Rate of Reaction (based on the experiment on this Factor: Temperature of reaction mixture) i.e. the effect of temperature on the rate of reaction between Sodium Thiosulphate solution and dilute sulphuric acid, H2SO4

hence, we define the 'Rate of Reaction' as follows:
The rate of reaction is operationally defined as "The time taken for the cross 'X' to disappear" when the "sodium thiosulphate solution is heated to various temperatures" and then reacted with dilute sulphuric acid, given that both the "dilute sulphuric acid and sodium thiosulphate solutions are of standard volumes and concentrations".

Note that I have inverted comma-ed the 'responding variable---the factor we are supposed to observe', the 'manipulative variable---the variable being obviously manipulated here'  and also the 'fixed variable---the variable being clearly controlled here'.

10. CLASSIFYING

Students must complete the given table according to the title . If the table is not provided, construct the table according to the classification given .

11. USING SPACE-TIME RELATIONSHIP

State the changes of the responding variable with time. Use relationship words like increases with / decreases with / remains constant with / increases proportionately with / etc. Do not use neutral relationship terms like affects / influences / changes with.