O Level – Chemistry

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The Mole – Key Points

1. Both relative atomic mass and relative molecular mass have no units.

2. Empirical formula an molecular formula may or may not be the same.

3. The total percentage composition of the elements in the compound must be 100%.

4. 1 dm^3 = 1000 cm^3

5. When calculating the Mr of a substance in the reaction, do not include the coefficient.

For more key points and exam based questions with full worked solutions please contact Mr Ong @98639833

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Chemical Calculations – Key Points

1. Spectator ions are ions that are not involved in a chemical reaction.

2. Stoichiometetry of the reaction is the relationship between the amounts of reactants and products involved in a chemical reaction.

3. Limiting reactant is the reactant that is completely used up in a reaction and determines the amount of products formed.

4. The concentration of a solution is given by the amount of a solute dissolved in a unit volume of the solution.

5. Molar concentration is the concentration of a solution expressed in mold/dm^3

6. The theoretical yield is the calculated amount of products that would be obtained if the reaction is completed.

7. Actual yield is the amount of pure products that is actually prodcued in the experiment.

For more key points and exam based questions with full worked solutions please contact Mr Ong @98639833

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Acids and Bases – Key Points

1. An acid is a substance that produces hydrogen ions, H+, when dissolved in water.

2. The strength of an acid refers to the extent to which the acid molecules dissociates when dissolved in water.

3. A base is a substance that reacts with an acid to form a salt and water only.

4. An alkali is a base that is soluble in water.

5. Neutralisation reaction is the reaction between an acid and a base to from a salt and water only.

6. The term concentration tells us how much a substance is dissolved in 1 dm^3

7. The term strength refers to how an acid or an alkali dissociates when dissolved in water.

8. The pH scale is a set is a set of numbers used to whether a solution is acidic, neutral or alkaline.

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Salt Preparation

Preparation of salt by reaction between acid and an insoluble base.

Example: Preparation of copper(II) sulfate from copper(II) oxide(insoluble base)

Step 1: Put sulfuric acid in a beaker.

Step 2: Add copper(II) oxide until no more can dissolve.
Copper(II) sulfate solution & unreacted copper(II) oxide

Step 3: Filter to remove the excess copper(II) oxide

Step 4: Collect the filtrate.

Step 5: Heat up the filtrate to evaporate the water to about 1/3 the original volume.

Step 6; Allow the filtrate to cool to room temperature so that copper(II) sulfate crystals.

Step 7: Wash the crystal with a little cold distilled water.

Step 8: Dry the crystal with filter paper

For more key points and exam based questions with full worked solutions please contact Mr Ong @98639833

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Oxidation and Reduction

Oxidation
– Gain of oxygen
– Gain of oxidation number
– loss of hydrogen
– loss of electron

Reduction
– loss of oxygen
– loss of oxidation number
– Gain of hydrogen
– Gain of electron

1. A redox reaction is a reaction involving oxidation and reduction.

2. An oxidising agent is a substance that causes oxidation on another substance.

3. An reducing agent is a substance that causes reduction on another substance.

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Metals

Important Definitions

1. An alloy is a mixture of metal with one or a few other elements.

2. The reactivity series is a series of metals arranged in the order of their chemical reactivity, from the most reactivity to the lease reactivity.

3. Displacement reaction of metals is a redox reaction in which a more reactive metal displaces a less reactive metal to form its salt solution.

4. Galvanising is the coating of iron or steel on zinc for protection against corrosion.

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Electrolysis

Important Definitions

1. An electrolytic cell is a set of apparatus that uses electrical energy to produce chemical reactions.

2. Electrolysis is the process of decomposition of a compound by electricity.

3. The anode is the positive electrode and the cathode is the negative electrode of an electrolytic.

4. An electrolyte is a substance that conducts electricity in the molten state or in aqueous solution.

5. Cations are positive ions and anions are negative ions

6. The discharge of ions is the process of gaining or losing electrons at the electrode.

7. An Inert electrode is an electrode that does not take part in chemical reaction during electrolysis.

8. A reactive electrode is an electrode that participates in chemical reactions during electrolysis.

9. Electroplating is the process of coating an object with a thin layer of metal using electrolysis.

10. A simple cell is a devise that uses chemical reactions to produce electricity.

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The Periodic Tables

Important Definitions

1. A group is a vertical column of elements in the Periodic Table.

2. A period is a horizontal row of elements in the Periodic Table.

3. A metalloid is an element that has the properties of both a metal and a non-metal

4. An alkali metals are the Group I elements.

5. The halogens are the Group VII elements.

6. The noble gases are the Group 0 or Group VIII elements.

7. The transition elements are a block metallic elements between Group II and II in the Periodic table.

8. A catalyst is a substance that increases the speed of chemical reaction.

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Energy Changes

Important Definitions

1. An exothermic reaction is a reaction that gives out heats energy to the surroundings.

2. An endothermic reaction is a reaction that absorbs heat energy from the surroundings.

3. Activation energy is the minimum energy that reacting particles must posses in order for a chemical reaction to take place.

4. An clergy profile diagram is used to show the activation energy of a reaction.

5. A fuel is a substance that burns easily in air to give out heat energy.

6. A fuel cell is a chemical cell in which the chemical energy of a fuel is converted directly into electrical energy.

For more key points and exam based questions with full worked solutions please contact Mr Ong @98639833

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2014 Secondary 4 Preparatory Course

11-Nov Mon 10.30am to 12pm 1.5 hrs Chemical Bonding 1

12-Nov Tue 10.30am to 12pm 1.5 hrs Chemical Bonding 2

13-Nov Wed 10.30am to 12pm 1.5 hrs The Mole 1

14-Nov Thu 10.30am to 12pm 1.5 hrs The Mole 2

15-Nov Fri 10.30am to 12pm 1.5 hrs Chemical Calculation 1

18-Nov Mon 10.30am to 12pm 1.5 hrs Chemical Calculation 2

19-Nov Tue 10.30am to 12pm 1.5 hrs Acids and Bases 1

20-Nov Wed 10.30am to 12pm 1.5 hrs Acids and Bases 2

21-Nov Thu 10.30am to 12pm 1.5 hrs Salts 1

22-Nov Fri 10.30am to 12pm 1.5 hrs Salts 2

If you need help in the above topics, please contact Angie @96790479 or Mr Ong 98639633

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Power Revision

O Level Chemistry – 2 hrs Each Lesson

1. Atomic Structure/Ionic, Covalent and Metallic Bonding – 2 lessons
2. Formulae & Equation Writing – 1 lesson
3. Mole & Chemical Calculations – 2 lessons
4. Acids and Bases – 1 lesson
5. Salts – 1 lesson
6. Chemical Analysis – 1 lesson
7. Metals – 2 lessons
8. Periodic Table – 2 lessons

If you need help in the above topics, please contact Angie @96790479 or Mr Ong 98639633

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Speed of Reaction – Important definitions

1. the speed of reaction is the amount of reactant used up or the amount of product obtained per unit time.

2. Activation energy is the minimum energy that the reacting particles must possess for a reaction to occur.

3. An effective collision is a collision that successful in producing a chemical reaction.

4. A catalyst is a substance that increases the speed of a chemical reaction.

5. An enzyme is a substance that catalyses biochemical reactions.

If you need help in the above topic, please contact Angie @96790479 or Mr Ong 98639633

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Ammonia – Important Definitions

1. A reversible reaction is a chemical reaction that can proceed in both the forward and reverse directions.

2. Haber process is an industrial process for making ammonia from nitrogen and hydrogen.

Operating conditions in the Haber process
Temperature – 450 deg C
Pressure – 200 – 300 atm
catalyst – Finely divided iron

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The Atmosphere and Environment – Important Definitions

1. Air pollution is the condition in which air contains substances that are harmful to living things or the environment. These substances are known as air pollutants.

2. A photochemical reaction is a chemical reaction caused by light or ultraviolet radiation.

3. Acid rain is rainwater with pH 4 or less than 4

4. Flue gases are waste gases produced when fossil fuels undergo commutation.

5. Chlorofluorocarbons CFCs are compounds containing the elements carbon, fluorine and chlorine.

6. The carbon cycle is the movement of carbon from carbon dioxide in the in the air through living things and back to the air again.

7. Greenhouse effect is the absorption of infrared radiation by some gases in the air which leads to atmospheric warming.

8. Global warming is the gradual warming of the Earth’s atmosphere due to the increased concentration of greenhouse gases in the atmosphere.

If you need help in the above topic, please contact Angie @96790479 or Mr Ong 98639633

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Introduction to Organic Chemistry – Important Definitions

1. Organic compounds are compounds that contain the element carbon.

2. A hydroarbon is an organic compound that contains only carbon and hydrogen.

3. A homologous series is a family of organic compounds with the same general formula and similar chemical properties.

4. A functional group is an atom or group of atoms that gives characteristic properties to an organic compound.

5. Petrochemicals are chemical made from petroleum or natural gas.

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