O Level – Chemistry

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Please post your O Level Chemistry questions here.

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Please use the resources O Level Chemistry Tuition.

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Chapter 1 – Kinetic Particle Theory

1. Explain why a solid have a fixed shape and volume using kinetic particle theory.

The particles of a solid are held together by very strong forces of attraction. They cannot move freely, and have only enough kinetic energy to vibrate and rotate about their fixed position.

2. Explain why a liquid does not have a fixed shape using kinetic particle theory.

The particles of a liquid are held together by weaker forces of attraction as compare with solid. They are arranged in a disorderly manner and can move freely by sliding over one another. Thus liquild does not have a fixed shape and take the shape of the container.

3. Explain why during the melting process, the temperature of the substance does not rise even though heating continue.

The temperature remains constant because all the heat energy taken in by the particles is used to overcome the forces of attraction holding the particles. A mixture of solid and liquid phases exist here.

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Chapter 2 – Measurement and Experimental Techniques

Collection of Gases

1) Displacement of water is suitable for collecting gases that are insoulble or slightly soluble in water.

Example: CO2, H2, O2

2) Downward delivery should be used to collect gases that are soluble in water and denser than air.

Example: Cl2, HCL

3) Upward delivery is used to collect gases that are soluble in water and less dense thar air

Example: NH3

From Pure Chemistry Tutor

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Chapter 3 – Purification and Separation

How to determine that a substance is pure?

If the substance has a fix melting and boiling point, the substance is pure. We can also use chromatography to check for pure substance.

From : O Level Chemistry Tutor

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Chapter 4 – Elements, Compounds and Mixture

An element is a pure substance that cannot be split into two or more simpler substances by physical and chemical processes.
Example copper and oxygen gas
Sugar C6H12O6 is not an element

A compound is a substance which contains two or more elements chemically joined together.
Example carbon dioxide and water

A mixture is a combination of two or more substances not chemically joined together.
Example sand and sodium chloride

From : O Level Chemistry Tutor

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Chapter 5 – Atomic Structure

1) Atoms are made up of protons, neutrons and electrons.
2) Proton number or atomic number is the number of protons in an atom.
3) Nucleon number is the number of protons and neutrons in an atom.
4) Isotopes are atoms of the same element with the same number of protons but different number of neutrons.

From : O Level Chemistry Tutor

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tut

Chapter 6 – Ionic Bonding

1) Noble gases are unreactive and do not form compounds because they have octet structure
2) Metals form postively charged ions (Cations)
3) Non-Metals usually form neagtively charged ions (Anions)
4) Metals react with non-metals to form ionic compounds.
5) An ionic bond is formed when electrons are transfeered from a metallic atom to a non-metallic atom.

From : O Level Chemistry Tutor

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Chapter 7 – Covalent and Metallic Bonding

1. A covalent bonding is bond formed by sharing of electrons between atoms
2. A single covalent bond consists of one shared pair of electrons
3. A double covalent bond consists of two shared pair or electrons.
4. A molecule is formed when two or more atoms are joined together by covalent bonds.
5. In a molecule, each atom has the electronic configuration of a noble gas.

From : O Level Chemistry Tutor

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Chapter 8 – Writing Chemical Equations

3 Basic steps

Step 1 : Write down the chemical formulae of the reactants and products to get the chemical equation.

Step 2 : Check the number of atoms of each element in the formulae on both sides of the equation are balanced.

Step 3 : Add the state symbols

From : O Level Chemistry Tutor

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Chapter 9 – The Mole

1. A mole of any substance contains 6 x 10 power 23 particles. This number is called Avogadro’s constant

2. Number of mole of atoms = mass of the element(g)/Ar

3. Number of mole of substance = Mass of the substance(g)/Mr

4. Molar mass refer to the mass of one mole of the substance.

From : O Level Chemistry Tutor

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Hi Jin Wei and Garyl

Attached is Redox MCQ answers

1. D
2. B
3. B
4. A
5. C

6. C
7. D
8. C
9. D
10. D

11. B
12. D
13. D
14. D
15. A

16. B
17. B
18. B
19. D
20. A

21. A
22. B
23. C

All the best for your coming QA and redox tests

From Mr Ong – Chemistry Tutor

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Chapter 10 – Chemical Calculations

What does an equation tell us?

A balanced chemical equation shows important facts about a reaction
a) The reactants
b) The products
c) The ratio of the amounts (in moles) of the reactants and the products
d) The state of each reactants/products if indicated

It is the relationship between the amounts (measured in moles) of reactants and products involved in a chemical reaction.

Exam based questions will be discussed in the lessons

O level Chemistry Tuition Tutor

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Chapter 11 – Salt

Key ideas

1. Soluble salts are prepared by the following methods:
a) Acid + a metal (excluding potassium, sodium, calcium, copper and silver)
b) Acid + an insoluble base
c) Acid + an insoluble carbonate
d) Acid + an alkali (titration method)

2. Insoluble salts are prepared by the precipitation reaction of two soluble salt solutions

O level Chemistry Tuition Tutor

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Chapter 12 – Acids and Bases

Q: What is an acid?
A: An acid is a substance which produces hydrogen ions, H+, when it is dissolved in water.

Q: What are the physical properties of acids?
A: 1. Acids have a sour taste.
2. Acids dissolve in water to form solutions which conduct electricity.
3. Acids turn blue litmus paper red.

Q: What are the chemical properties of acids?
A: 1. Acids react with reactive metals to form hydrogen gas and a salt.
metal + acid —–> salt + hydrogen

2. Acids react with carbonates to form a salt, carbon dioxide and water.
carbonate + acid —–> salt + water + carbon dioxide

3. Acids react with metal oxides and hydroxides to form a salt and water only.
metal oxide + acid —–> salt + water

metal hydroxide + acid  salt + water

Q: Do all metals react with acid?
A: No, When unreactive metals such as copper or silver are added to dilute acids, there is no reaction.

Contact Mr Ong @9863 9633 for much key ideas on acids and bases

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