Writing hypothesis, relationship, inference and operational definition.

Hypothesis
The higher the manipulated variable, the higher/lower the responding variable.
or
If the manipulated variable is higher, the responding variable is higher/lower.

eg :
The higher the temperature, the higher the rate of transpiration.
If the temperature is higher, the rate of transpiration is higher.

Relationship (write just like the way you wrtie the hypothesis)
State the relationship between the size of container and the time taken for the candle to extinguish.

Eg:
The bigger the size of container, the longer the time taken for the candle to extinguish.
If the the size of container is bigger, the time taken for the candle to extinguish is longer.

 Inference
The responding variable depends on the manipulated variable.
or
The manipulated variable affects the responding variable. 

Eg:
The brightness of the bulb depends on the length of the wire// Length of wire affects brightness of bulb.
The stability depends on the way the student stands// The way the student stands affects stability.

***Please Take Note***
From next year onwards (2011), the above way of writing inference will not be accepted anymore.
The correct way of writing inference is the answer must have cause and effect (with reason).
eg : Write one inference about the beg in situation L.
Ans : Bag in L is lighter because the time taken to lift it is shorter.
eg : Write one inference about the soot produced during the burning of the distillate.
Ans : As the boiling points gets higher, more soot is produced because the fraction is less combustible. 

Operational definition
------------ is the responding variable.
Eg:
State the operational definition for combustion.

Ans :Combustion is the time taken for the candle to extinguish.


State the operational definition for work done based on diagram 8.1.
Ans : Work done is the time taken to lift the bag/ the reading of the stopwatch.

Paper 2

Sample Answer-Question 8 (2009)

8 (a) Diagram 8.1 shows two different containers, J and K. The grasshoppers in both containers are similar.

(i) State one difference between the grasshoppers in containers J and K after two days.

    Ans : The grasshopper in J died but the grasshopper in K is still alive.

              (must state both grasshopper J and K)

(ii) What inference can be made based on the situation in containers J and K?

     Ans : The grasshopper depends on air/oxygen to live.

(b) Diagram 8.2 shows four similar candles being covered by four containers, K, L, M and N, of different sizes.

(i) In Table below, record the time taken for the candle in container M to extinguish.

    Ans : 11 s

(ii) Predict the time taken for the candle in container N to extinguish.

    Ans : 11.1 – 60s

(iii) Based on the data in Table 8.1, draw a bar chart to show the time taken for the candle to extinguish in each container.

    Ans : Transfer all points(1 m)

             Bar same width (1 m)

(c) Based on the bar chart drawn in 8(b)(iii), state the relationship between the size of containers and the time taken for the candles to extinguish.

    Ans : The bigger the size of the container, the longer the time taken for the candle to extinguish.

(d) State the responding variable in this experiment.

     Ans : Time //time to extinguish

(e) Predict the time taken for the candle in container K to extinguish if the air in the container is replaced with exhaled air.

    Ans : < 5 s //shorter time (Reject : 0 sec)

(f) State the operational definition for combustion.

    Ans : Combustion is the time taken for the candle to extinguish

PMR Science

      Paper 1

1. All topics from forms 1, 2 and 3 are included in PMR.

2. Read the questions first and then read all the choices before choosing the answer even though the first or second choice looks correct.
3. Circle/underline words like all, none, always, never, only, not and except to help avoid careless mistakes.    

4. If the answer is not apparent, use the elimination process. Cross out all choices which are clearly incorrect, then choose from the choices that are left.

5. Answer every question. Do not leave out any question as you will stand a chance of scoring some marks than just leaving it blank.

6. Check your answer sheet to make sure you have filled in only one answer  for each question. Make sure you have filled the correct answer which corresponds to the question.

7. If you change an answer, make sure you erase the first answer completely.