Wednesday, 27 July 2011

To make a hypothesis

How to construct or make a hypothesis?

First, you must understand that a hypothesis is a statement that relates a manipulated variable with a responding variable.
Therefore, you must be able to identify the manipulated variable and the responding variable for an experiment.

For example, in experiment to determine the effect of temperature on the rate of reaction between sodium thiosulphate and sulphuric acid.

The manipulated variable is temperature,  and the responding variable is rate of reaction.

Therefore, the statement of hypothesis is: When the temperature of sodium thiosulphate increases, the rate of reaction with sulphuric acid increases.

Monday, 25 July 2011

Operational Definition

Operational definition is a statement that shows the "what you do and what you observe".

For example, the operational definition for coagulation of latex:

The "what you do" is... when acid is added to latex..

The "what you observe " is.... white solid is formed.

Therefore the operational definition for the coagulation of latex is ..When acid is added to latex, white solid is formed. (SPM 2008)

The operational definition for the neutralisation of acid or alkali could be... When acid is added to alkali with a few drops of phenolphthalein, the pink solution changes to colourless.

The operational definition for the reactivity of Group 1 elements towards water:
When a metal which is lower down in Group 1is put into a basin filled with water, the movement of the metal on the water surface is faster // more vigorous// the flame produced is bigger or brighter.

Teacher Norini hopes that you girls and boys have some idea now the meaning of operational definition. Well, you can always ask Teacher Norini if you don't.

Friday, 22 July 2011

Constructs in Paper 3

In Paper 3 Chemistry 4541/3, there are several constructs to be understood and solved.
For example, making hypothesis, aim @ problem statement, naming variables, to state the operational definition and so on.

Question for the day!

What is operational definition?

For example: Give the operational definition for the neutralisation of acid and alkali.

Teacher Norini will give the answer later....

Monday, 18 July 2011

Difference in pH value between hydrochloric acid and ethanoic acid.

1. Hydrochloric acid is a strong acid.
2. Therefore, acid can ionise completely in water
3. to produce high concentration of hydrogen ion
4. Ethanoic acid is a weak acid.
5. This acid can ionise partially in water
6. to produce low concentration of hydrogen ion
7.  When the concentration of hydrogen ion is higher, the pH value is lower

Salam boys and girls!


Hydrochloric acid 1.0 mol dm-3 has 2 pH value.
Ethanoic acid 1.0 mol dm-3 has 6 pH value.

Explain the difference in pH value for the acids

Sunday, 17 July 2011

Salam. Sorry for the late reply for the answers to previous questions.
Ok, the answer to why alloy is harder than its's pure metal is:
1. Atoms of foreign element added to metal are of different size from atoms in pure metal.
2. These atoms will disrupt the orderly arrangement of the atoms in metal.
3. When force is applied, the foreign atoms will reduce the sliding of the atoms over each other.
4. Thus making alloy harder and stronger.

Pure metal is soft, malleable and ductile because:
1. Atoms are of the same size
2. Atoms are arranged  in layers and orderly manner.
3. When force is applied the layers of atoms can easily slide over each other

Note: make sure you know how to draw the diagram for the arrangement of atoms in alloy and pure metal

Wednesday, 13 July 2011



Teacher Norini will give the answer tomorrow.