Thursday, April 16, 2009


Captions showing Form 4 A students are having Chemistry class - calculation of empirical formula and molecular formula by teacher, Pn Habshah binti Abdul Kudus.

Wednesday, April 15, 2009


Key Concepts

  • Empirical Formula of a compound shows the ratio of elements present in a compound.
  • Molecular Formula of a compound shows how many atoms of each element are present in a molecule of the compound.
  • The empirical formula mass of a compound refers to the sum of the atomic masses of the elements present in the empirical formula.
  • The relative molecular mass (formula mass, formula weight or molecular weight) of a compound is a multiple of the empirical formula mass.
    RMM = n x empirical formula mass
  • Empirical Formula can be calculated from the percentage (or percent) composition of a compound.
Molecular formulas and empirical formulas are sometimes the same: Molecular formulas and empirical formulas are not always the same:
    The molecular formula for hydrogen peroxide is H2O2, a 1 to 1 ratio.
    The formula is correct. Remember that peroxide is a polyatomic ion with a charge of -2.
    Reduce the subscripts to the lowest form.
    The empirical formula for hydrogen peroxide is HO, a 1 to 1 ratio.
Calculating Empirical Formulas:
    Subscripts in a chemical formula are usually thought of as a ratio of atoms.
    Subscripts can also be thought of as a ratio of moles . . . . .
    a mole being the number of atoms needed
    to equal the atomic mass number of an element.

    To determine an empirical formula, one must determine the mole ratio.

Monday, April 13, 2009


Key Info

  • The scientific method is a way to ask and answer scientific questions by making observations and doing experiments.
  • The steps of the scientific method are to:
    • Ask a Question
    • Do Background Research
    • Construct a Hypothesis
    • Test Your Hypothesis by Doing an Experiment
    • Analyze Your Data and Draw a Conclusion
    • Communicate Your Results

  • It is important for your experiment to be a fair test. A "fair test" occurs when you change only one factor (variable) and keep all other conditions the same.

Sunday, April 12, 2009


Question: What Is Chemistry?
Answer: If you look 'chemistry' up in Webster's Dictionary, you'll see:

"chem·is·try n., pl. -tries.
1. the science that systematically studies the composition, properties, and activity of organic and inorganic substances and various elementary forms of matter.
2. chemical properties, reactions, phenomena, etc.: the chemistry of carbon.
3. a. sympathetic understanding; rapport. b. sexual attraction.
4. the constituent elements of something; the chemistry of love. [1560-1600; earlier chymistry]."

My glossary definition is the short and sweet, "scientific study of matter, its properties, and interactions with other matter and with energy".

An important point to remember is that chemistry is a science, which means its procedures are systematic and reproducible and its hypotheses are tested using the scientific method. Chemists, scientists who study chemistry, examine the properties and composition of matter and the interactions between substances. Chemistry is closely related to physics and to biology. As is true for other sciences, mathematics is an essential tool for the study of chemistry.


Mole is abbreviated to mol and given the symbol n

1 mole contains the same number of particles as there are in 12g of carbon-12 atoms by definition.
This number is called Avogadro's number or Avogadro's constant (NA) and is equal to 6.022 x 10 23 particles.

1 mole of a pure substance has a mass in grams equal to its Relative Atomic Mass (RAM) or its Relative Molecular Mass (RMM) [also known as molecular weight (MW) or Relative Formula Mass (RFM) or formula weight (FW)].This is often referred to as the molar mass.

1 mole of an ideal gas has a volume of:
22.4 litres (22.4L) at S.T.P.
[Standard Temperature and Pressure, 0 oC (273K) and 101.3kPa (1 atm)]

24.47 litres (24.47L) at S.L.C
[Standard Laboratory Conditions, 25 oC (298K) and 101.3kPa (1atm)]

Avogadro's Number (NA)
1 mole of atoms or molecules contains 6.022 x 10 23 atoms or molecules

Saturday, April 11, 2009


Chemistry is the science of materials, their composition and structure, and the changes they undergo. Quite a broad topic! Chemistry is such a large discipline that it is generally divided into six main branches:

* Analytical chemistry is concerned with the separation, identification, and composition of materials.

* Organic chemistry is the chemistry of most carbon compounds.

* Inorganic chemistry is (you guessed it) the chemistry of materials other than those classed as organic.

* Physical chemistry involves the study of the physical characteristics of materials and the mechanisms of their reactions.

* Biochemistry includes the study of materials and processes that occur in living things.

* Nuclear chemistry involves the study of subatomic particles and nuclear reactions.

Monday, April 6, 2009


Today we are doing an experiment to find the empirical formula of magnesium oxide


SPM Chemistry Form 4

Form 4 Chemistry
1. Introduction To Chemistry
1.1 Understanding chemistry and its importance
1.2 Synthesising scientific method
1.3 Incorporate scientific attitudes and values in conducting scientific investigations
2. The Structure Of The Atom
2.1 Analysing matter
2.2 Changes in the state of matter
2.3 Synthesising atomic structure
2.4 Understanding isotopes and assessing their importance
2.5 Understanding the electronic structure of an atom
3. Chemical Formulae And Equations
3.1 Understanding and applying the concepts of relative atomic mass and relative molecular mass
3.2 Analysing the relationship between the number of moles with the number of particles
3.3 Analysing the relationship between the number of moles of a substance with its mass
3.4 Analysing the relationship between the number of moles of a gas
3.5 Synthesising chemical formulae
3.6 Interpreting chemical equations
4. Periodic Table of Elements
4.1 Analysing the Periodic Table of Elements
4.2 Analysing Group 18 elements
4.3 Analysing Group 1 elements
4.4 Analysing Group 17 elements
4.5 Analysing elements in a period
4.6 Understanding transition elements
5. Chemical Bonds
5.1 Understanding formation of compounds
5.2 Synthesising ideas on formation of ionic bond
5.3 Synthesising ideas on formation of covalent bond
5.4 Analysing properties of ionic and covalent compounds
6. Electrochemistry
6.1 Understanding properties of electrolytes and non-electrolytes
6.2 Analysing electrolysis of molten compounds
6.3 Analysing the electrolysis of aqueous solutions
6.4 Evaluating electrolysis in industry
6.5 Analysing voltaic Cell
6.6 Synthesising electrochemical series
7. Acids And Bases
7.1 Analysing characteristics and properties of acids and bases
7.2 Synthesising the concepts of strong acids, weak acids, strong alkalis and weak alkalis
7.3 Analysing concentration of acids and alkalis
7.4 Analysing Neutralization
8. Salt
8.1 Synthesising Salts
8.2 Synthesising qualitative analysis of salts
8.3 Practising to be systematic and meticulous when carrying out activities
9. Manufactured Substances in Industry
9.1 Understanding the manufacture of sulphuric acid
9.2 Synthesising the manufacture of ammonia and its salts
9.3 Understanding Alloys
9.4 Evaluating uses of synthetic polymers
9.5 Applying uses of glass and ceramics
9.6 Evaluating uses of composite materials

About Me

My photo
The world is still a very nice place to live even though we have millions of problems.