O Level Chemistry & IP Chemistry Notes by 10 Year Series Author - Chemistry Specialist

O Level Chemistry Made Easy

O-Level & IP Pure Chemistry: The Reactivity Series of Metals

Reactivity Series of Metals

In the previous blog post, we have discussed on the physical properties of pure metals as well as the four main reasons why we use metals in the form of alloys.

Today, we shall take a look at The Reactivity Series of Metals.

Metals are listed in the Reactivity Series from the most reactive to the least reactive.

This is useful because it allows you to predict how a particular metal will undergo a certain chemical reaction. For example, the Reactivity Series will show you immediately why coins made of zinc metal look dull after some time while silver and gold coins remain bright and shiny for long period of time. This is simply due to the fact that zinc is more reactive than gold and thus it will react faster with air.

In Singapore, whether you are taking the GCE O-Level Pure Chemistry syllabus or any of the IP Chemistry syllabus, you will need to remember the sequence of metals in the Reactivity Series.

As such, we use mnemonics (super memory techniques) to help our Sec 3 and 4 O-Level Pure Chemistry and IP Chemistry Tuition Class students to recall the list of metals. This is really useful. In fact, you can come out with your own memorising method if you want. Else, just use the one that is presented here. You can download your copy of the Reactivity Series of Metals.

The Reactivity Series of Metals

MetalSymbolMnemonic
PotassiumKPlease
SodiumNaStop
CalciumCaCalling
MagnesiumMgMe
Aluminium *AlA
ZincZnZebra
IronFeInstead
TinSnTell
LeadPbLaura
(Hydrogen)HHow
CopperCuCopper
SilverAgStrengthens
GoldAuGold

* Aluminium tends to oxidise readily in air to form aluminium oxide, Al2O3(s). As such, aluminium is not very reactive in our everyday life because it is covered (and thus protected) by the layer of Al2O3(s). Note that the layer of Al2O3(s) has been removed before experiments were conducted by scientists to determine the position of aluminium in the Reactivity Series of Metals.

Special Note:

The Reactivity Series is actually determined by scientists through the reactions of a list of common metals with water, steam and dilute hydrochloric acid. We will discuss this in more detail in the next blog post. Do look out for it!

YouTube Video Tutorial on The Reactivity Series of Metals

You can watch the YouTube Video below to learn how to memorise the list of metals in the Reactivity Series.

Click on the following link for the video on O-Level Chemistry . IP Chemistry: The Reactivity Series of metals

Length of Video: 8.04 minutes

 

I hope you find the content easy for your understanding and if you have any questions, leave me a comment below. Feel free to share this blog post with your friends.

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PS: Under related articles below, there are several blog post discussions and questions related to Metals. You can also do a keyword search using the search box at the top right hand corner.

PPS: Do check out the Comments Section below to check out mnemonics shared by other Chemistry Teachers/Tutors/Students. Feel free to contribute your version too.

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O-Level & IP Pure Chemistry: Physical Properties of Pure Metals and Alloys

Is Iron Man made of a Pure Metal or An Alloy?

Metals are commonly being used in our everyday lives.

For example, silver and gold are commonly used as jewellery because of their shiny appearance. Copper is widely used in metal wires and cables. Titanium and zirconium are also commonly used for making aircraft and space shuttle parts.

Pure Metals

In general, metals have the following physical properties:

  • Usually have high densities
  • Malleable and ductile
  • Usually have high melting points and boiling points i.e. exists as solids at room temperature
  • Good conductors of electricity (and heat)

These physical properties can be easily explained by looking at the structures of metal.

Physical Properties of Metals

1) Usually have high densities

Atoms in a metal are packed tightly in layers and are held together by strong metallic bonds. As such, there is large number of atoms per unit volume i.e. high densities.

2) Malleable and ductile

Malleability refers to the ability to be beaten or hammered into shapes without breaking. Ductility refers to the ability to be stretched or drawn into wires without breaking. In pure metals, same size atoms are packed closely together in a regular pattern. When a force is applied to a metal, the layers of metal atoms can slide past each other. As such, pure metals are known to be soft, malleable and ductile.

In pure metals, same size atoms are packed together in a regular arrangement.

3) Usually have high melting points and boiling points

In the metal lattice, the atoms lose their valence (outermost shell) electrons and become positively charged metal ions. The valence electrons are said to be delocalised out into the empty spaces (‘sea’). Strong electrostatic forces of attraction exists between the positively charged metal ions and the negatively charged electrons. Large amount of energy is required to overcome these forces.

‘Sea’ of delocalised electrons surrounding the positively charged metal ions in the giant metallic lattice structure

4) Good conductors of electricity (and heat)

The valence (outermost shell) electrons delocalised into the empty spaces (‘sea’) and are able to move freely within the metal lattice. These ‘sea’ of delocalised electrons are mobile
(free moving) and act as charge carriers which help to conduct electricity and heat.

Pure metals have many useful properties but they are not widely used because of two main reasons:

  • Pure metals are too soft and malleable
  • Pure metals may react with air and water i.e. corrode easily

As such, we often use alloys instead of the pure metals.

Alloys

An alloy is defined as a mixture of a metal with at least one other element. The element(s) added can be either a metal or a non-metal.

4 Main Reasons Why Metals are used as Alloys:

  • To make metals stronger and harder
  • To make metals more resistant to corrosion
  • To improve the appearance of metals
  • To lower the melting points of metals

1) To make metals stronger and harder

The most common question that students will be asked in their Chemistry tests and examinations is how does alloying increase the strength and hardness of a pure metal.

First of all, in an alloy, the atoms of the main metal and the element(s) added have different sizes. This disrupts the regular arrangement of the atoms in the pure metal. Atoms of different sizes cannot slide past each other easily when a force is applied. As such, an alloy is stronger, harder and less malleable than the pure metal itself.

Atoms of different sizes disrupt the regular arrangement in pure metals

For the purpose of GCE O-Level Pure Chemistry and IP Chemistry examinations, students would need to know the following examples of alloys:

  • Brass = Copper + Zinc
  • Bronze = Copper + Tin
  • Steel = Iron + Carbon
  • Stainless Steel = Iron + Carbon + Nickel + Chromium

Let’s take a look at a potential question which you might be tested in the Chemistry examination. This is modified from a question in Paper 2 (Written Paper) of the Nov 2011 GCE O-Level Pure Chemistry Examination in Singapore.

Question:

Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinoids series of the periodic table.

(i) Describe the bonding in uranium. [2]

Answer: Strong electrostatic forces of attraction between the positively uranium ions and the ‘sea’ of delocalised electrons in the giant metallic lattice structure.

(ii) Explain what happens when an electric current passes through uranium. [1]

Answer: The ‘sea’ of delocalised valence electrons in uranium are free moving and they act as charge carriers and move throughout the metallic structure.

Source: Paper 2, Nov 2011 GCE O-Level Pure Chemistry Examination

2) To make metals more resistant to corrosion

Coins that we used in our everyday lives are made of cupronickel, which is an alloy of copper and nickel. It does not corrode easily.

3) To improve the appearance of of metals

Pewter is an alloy of tin, antimony and copper. It is commonly used to make ornaments such as key chains and decorative displays because it looks more beautiful than pure tin itself.

4) To lower the melting points of metals

The main method used in the industry to join two metal parts together is through the use of soldering. The solder material is usually an alloy of tin and lead, and it has a lower melting point than most metals.

Can you draw simple diagrams to show the difference in the arrangement of atoms between copper and bronze?

YouTube Video Tutorial on Physical Properties of Pure Metals and Alloys

You can watch the YouTube Video below to have an even clearer idea about the properties of pure metals and the reasons why metals are often used in the form of alloys .

Click on the following link for the video on O-Level Chemistry . IP Chemistry: Physical Properties of Pure Metals and Alloys

Length of Video: 12.32 minutes

Before we end this blog post, a quick food-for-thought exam-based question for you to ponder:

Q) Can you draw simple diagrams to show the difference in the arrangement of atoms between copper and bronze?

Source: Possible exam question in O-Level Pure Chemistry and IP Chemistry

I hope you find the content easy for your understanding and if you have any questions, leave me a comment below. Feel free to share this blog post with your friends.

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PS: In the next blog post, i will share with you on the Reactivity Series of Metals. Do look out for it. Also, under related articles below, there are several blog post discussions and questions related to Metals. You can also do a keyword search using the search box at the top right hand corner.

PPS: If you need help with your O-Level Pure Chemistry and IP Chemistry, do join us in our weekly O-Level Pure Chemistry & IP Chemistry Tuition Class. Get it right the first time!

2019 O-Level Pure Chemistry MCQ Paper 1 Answers (Subject code: 6092)

2019 O Level Pure Chemistry 6092 MCQ Paper 1 Answers and Explanations by Mr Sean Chua Chemistry Tutor Singapore

Check out the suggested answers for the recent 2019 O Level Pure Chemistry (subject code: 6092) Paper 1 MCQ by Singapore’s highly recommended O Level Chemistry and IP Chemistry tutor Mr Sean Chua who has been conducting O Level Chemistry and IP Chemistry Tuition Classes since 1999.

Answer Key to 2019 O Level Pure Chemistry Paper 1 MCQ:

1.     A (Topic: Experimental Techniques)
2.     B (Topic: Qualitative Analysis QA)
3.     C (Topic: Purification & Separation Techniques)
4.     D (Topic: Qualitative Analysis QA)
5.     D (Topic: Atomic Structure)
6.     D (Topic: Chemical Bonding & Structural Properties)
7.     C (Topic: Chemical Bonding & Structural Properties)
8.     B (Topic: Macromolecules)
9.     A (Topic: Chemical Bonding & Structural Properties)
10.  C (Topic: Mole Concept & Chemical Calculations)
11.  D (Topic: Mole Concept & Chemical Calculations)
12.  C (Topic: Mole Concept & Chemical Calculations)
13.  B (Topic: Electrolysis)
14.  C (Topic: Electrolysis)
15.  A (Topic: Energy Changes)
16.  D (Topic: Energy Changes)
17.  D (Topic: Speed of Reaction)
18.  B (Topic: Speed of Reaction)
19.  B (Topic: Redox Reaction)
20.  A (Topic: Acids, Bases & Preparation of Salts)
21.  C (Topic: Periodic Table & Group Trends)
22.  A (Topic: Acids, Bases & Preparation of Salts)
23.  C (Topic: Air & The Atmosphere)
24.  C (Topic: Periodic Table & Group Trends)
25.  A (Topic: Periodic Table & Group Trends)
26.  B (Topic: Periodic Table & Group Trends)
27.  B (Topic: Periodic Table & Group Trends)
28.  A (Topic: Metals & Reactivity Series)
29.  A (Topic: Electrolysis)
30.  A (Topic: Metals & Reactivity Series)
31.  D (Topic: Air & The Atmosphere)
32.  A (Topic: Organic Chemistry)
33.  C (Topic: Organic Chemistry)
34.  A (Topic: Organic Chemistry)
35.  B (Topic: Organic Chemistry)
36.  B (Topic: Macromolecules)
37.  B (Topic: Macromolecules)
38.  C (Topic: Organic Chemistry)
39.  D (Topic: Organic Chemistry)
40.  A (Topic: Macromolecules)

Summary of Topics Tested in Paper 1 Multiple Choice Questions:

  • Experimental Techniques (x 1 question)
  • Purification & Separation Techniques (x 1 question)
  • Atomic Structure (x 1 question)
  • Chemical Bonding & Structural Properties (x 3 questions)
  • Acids, Bases & Preparation of Salts (x 2 questions)
  • Qualitative Analysis QA (x 2 questions)
  • Mole Concept & Chemical Calculations (x 3 questions)
  • Periodic Table & Group Trends (x 5 questions)
  • Metals & Reactivity Series (x 2 questions)
  • Speed of Reaction (x 2 questions)
  • Energy Changes (x 2 questions)
  • Redox Reaction (x 1 question)
  • Electrolysis (x 2 questions)
  • Air & The Atmosphere (x 2 questions)
  • Organic Chemistry (x 6 questions)
  • Macromolecules (x 4 questions)

Analysis of O Level Pure Chemistry Paper 1 MCQ:

For 2019 O Level Pure Chemistry Paper 1 MCQ, Cambridge International Examiners are testing O Level Pure Chemistry students heavily on Periodic Table & Groups Trends, Organic Chemistry and Macromolecules. A total of 15 out of 40 questions were being tested based on those topics.

Topics on Kinetic Particle Theory and Ammonia were not tested at all. For the past 10-15 years, we usually have more questions on Acids, Bases & Preparation of Salts but for this year, we have only 2 questions.

In general, this paper is considered quite easy for those students who have strong foundation of their Chemistry Concepts and associated keywords. There weren’t any extremely difficult or tricky questions this year.

Lastly, there were 3 repeat questions based on the O Level Pure Chemistry Ten Year Series (2009-2018). Question 10 came out in 2014, Question 17 came out in 2016 and Question 38 came out in 2011.

Hope you find the suggested answers and the analysis useful towards your learning. Feel free to share it with your friends.

For Sec 3 & 4 Pure Chemistry and IP Chemistry students who are aiming to Pass Chemistry with Distinction, join us in our weekly Chemistry tuition classes (available in Bras Basah & Bishan) to stay consistent in 2020.

Personally taught by Mr Sean Chua. Only 4 classes every year. WhatsApp or Call us at 88290998 now!

O-Level-Pure-Chemistry-Ten-Year-Series-Topical-by-Sean-Chua

Get your copy of 10 Year Series O Level Pure Chemistry book by SAP publisher for the full step solutions and explanations. Suitable for IP Chemistry students too!

Being invited book author by SAP publisher (authorised by Ministry of Education) Mr Sean Chua is not allowed to show much of the suggested solutions openly.

Check out Mr Sean Chua collection of Chemistry videos to help you to learn Chemistry better, faster and easier.

Post Mortem (Suggested Answers) for 2019 GCE O-Level Pure Chemistry Paper 2 Written Paper and Tips for Paper 1 MCQ:

This post is relevant to students taking the GCE O-Level Pure Chemistry (syllabus code: 6092) examination currently.

Paper 2 Written Paper this year is considered quite do-able by most students. Even though it is not the most difficult written paper we have seen in the last 10 years, there are still couple of “weird” questions which some students will find it hard to apply to.

In fact, i am hearing more students telling me that they are not very confident of doing well for Paper 2 Written Exam. Many commented that this year’s questions are unusual as compared to the last 10 years when they compared it to questions found in the Pure Chemistry Ten Years Series books. They found that many of the major topics/concepts which are usually tested in Paper 2 did not appear this year! They also complained that the space/lines given for them to write the answers for quite a number question in the exam script is insufficient also.

At Winners Education, we are quite “lucky” this year. Many of the fundamental questions and application questions that were discussed in our Sec 4 Saturday and Sunday weekly tuition classes as well as my Sec 4 Friday Revision Class came out. I hope our students revised those concepts and questions which we have discussed previously and performed well for this Paper 2.

Post Mortem (Topical Analysis) of Paper 2 Written Paper:

Here is the list of topics and concepts that are being tested in the recent Pure Chemistry Paper 2 Written Paper:

Question A1 is on Organic Chemistry – Macromolecules. [I mentioned to our students that one of these years, Cambridge Examiners are going to go heavy on Macromolecules because they know students are quite weak in this topic]

Question A2 is on Atomic Structure – Isotopes as well as on Chemical Bonding – Physical Properties of Substances. [glad we emphasised on the importance of the definition of Isotopes during the revision phase]

Question A3 is on Solubility of Salts as well as on Qualitative Analysis (QA) – Test for Cations using aqueous ammonia and sodium hydroxide solution & test for nitrate anion. [Also told my students that QA was not really being tested in Paper 3 Practical Exam, so it should come out in Paper 2 Written Exam and Paper 1 MCQ].

Question A4 is on Kinetic Particle Theory – Diffusion of Gases which depends on molecular mass of gases as well as the surrounding temperature. [glad we covered this basic topic during revision phase and not skipped it like most tuition centres as well as schools]

Question A5 is on Acids & Bases – specifically on Types of Oxides and how their solutions affect the litmus paper (indicator). Students are also tested on Chemical Bonding – Dot-and-cross diagram for Na2O (an ionic compound) as well as on Mole Calculations – to calculate the Theoretical yield and then % Yield. [Types of Oxides as well as Indicators are important concepts which we emphasised greatly during the revision phase].

Question A6 is on the application of Metals & Reactivity Series – Sacrificial Protection and Barrier Protection of steel underground pipes. [this is an important concept and we covered at great length on its application].

Question A7 is on Electrolysis – How the use of different metal electrodes in Simple Cells produces different voltages. [glad we covered both Electrolytic Cells as well as Simple Cells. It comes to a shock to many students in Singapore that Electrolytic Cells did not come out at all. Nobody expected Cambridge Examiner to test on the “less discussed” Simple Cells].

Question B8 is a Data Source Question on Bleach. Students are tested on several concepts:

  • Chemical Bonding on Dot-And-Cross Diagram
  • Redox Reactions on Oxidation States [i repeated the concepts and application of Oxidation States at least twice during revision phase]
  • Mole Calculations – Calculate and show how the % by mass of chlorate (I) ion in calcium chlorate (I) is higher than sodium chlorate (I)
  • Solve questions by sourcing from the data / info given

Question B9 is on Rate of Reaction – Effect of Catalyst

  • First part of the question is actually based on the concept on Heterogenous Catalyst in GCE A-Level H2 Chemistry. Considered a fair question still, since diagram is given which clearly show what happens during the catalytic process. Students just need to follow each stage of the diagram closely and describe what they see. [as expected, Cambridge Examiners want students to follow the question and apply].
  • Students are then asked to complete and label two energy profile diagrams, one with and one without the catalyst. So this is another basic question which student should score well.
  • As usual, students are finally asked on how catalyst increases the rate of reaction based on Collision Theory.

Question B10 Either is on Organic Chemistry

  • This question is about the oxidation of ethanol to ethanal (not in GCE O-Level Pure Chemistry syllabus) to ethanoic acid.
  • It starts by asking students to name two substances that can oxidise ethanol to ethanoic acid. The two substances are obviously oxidising agents.
  • It then asks to name and give the formula for the third member of the alcohol and carboxylic acid homologous series.
  • The structural formula of ethanal is given in the question and ethanal is stated as the second member of the aldehydes homologous series (not in GCE O-Level Pure Chemistry syllabus once again). Students are then asked to draw out the structural formula of the first member of the aldehydes homologous series.
  • Next part of the question gave 3 equations and students are asked to write out the overall equation. They are also being asked to identify the catalyst in the multiple step reactions [which I have discussed with our students and have told them it is very common when it comes to GCE A-Level H2 Chemistry Exam and the Cambridge Examiners may just test them in GCE O-Level Pure Chemistry Exam anytime].

Question B10 OR is also on Organic Chemistry

  • Question starts by giving three isomers (two carboxylic acids and one ester).
  • Students are first being asked to describe and explain the effect on the Universal Indicator on each of the isomers.
  • Students are then asked to determine the carboxylic acid and alcohol which will give the ester isomer.
  • Students are then finally being asked to determine the empirical formula and molecular formula of another isomer (Mole Calculation).
  • [glad we covered extensively on Organic Chemistry during the revision phase].

So that is Paper 2 SQ which has a weightage of 50%. I will not be sharing the suggested answers over here since I don’t want to create any panic for students currently taking the examination now (in case you didn’t get the correct answer). I will be sharing my suggested answers in 2020 edition of GCE O-Level Pure Chemistry Ten Years Series books by SAP Publishers. The books should hit Popular Bookstores and school book shops in February 2020 and will serve as a very good reference guide for students taking GCE O-Level Exam in 2020.

Note that this is not the final exam for Pure Chemistry. There is still the last paper which will determine the final grade of your Pure Chemistry.

Fast forward, students will finish up their GCE O-Level Examination with their last paper – Pure Chemistry Paper 1 MCQ which has a weightage of 30%.

Students must really treasure this paper. Doing well in it will definitely pull up their overall Pure Chemistry grade.

In view that this is the last paper of the whole GCE O-Level Examination, many students would have gotten complacent. This is the best time for you to catch up, simply by revising well and aim to score full marks (40/40)for it! It is possible. Every year, our students report back to say that they manage to Score 100% for O-Level Pure Chemistry Paper 1 MCQ. This is as good as saying they have secured 30%!

Now, let’s take a look at what are the possible topics or concepts which might be tested for Paper 1 MCQ on 15th November 2019.

Usually, the same concepts will not be tested twice in the same year. So, for those concepts already tested in Paper 2 Written Paper, we most likely won’t see them again in Paper 1 MCQ. This also means, those topics/concepts not tested in Paper 2 Written Paper will have a very high chance to be tested in Paper 1 MCQ.

Following are the topics/concepts which may come out in Paper 1 MCQ:

1. Kinetic Particle Theory

  • Changes of states of matter

2. Measurement and Experimental Techniques

  • Appropriate apparatus for measuring mass, time, temperature and volume of liquids and gases
  • Selecting appropriate apparatus for collecting a sample of gas (displacement of water, downward delivery, upward delivery techniques).
  • Drying of gas using concentrated sulfuric acid, quicklime (calcium oxide) and fused calcium chloride.

3. Separation and Purification Techniques

  • Methods of separating and purifying mixtures of different states of matter using techniques such as filtration, evaporation to dryness, crystallisation, magnetic separation, sublimation, simple distillation, fractional distillation, use of separating funnel as well as chromatography.
  • Methods of determining the purity of substances such as melting point, boiling point and chromatography.

4. Elements, Compounds and Mixtures

Identifying whether a substance is an element, compound or mixture

Differences between compounds and mixtures

5. Atomic Structure

  • Electrons, protons and nucleus in an atom
  • Atomic number (proton number) and atomic mass (nucleon number)
  • Similarity and difference in isotopes

6. Chemical Bondings

  • Differences in the ionic bonding, chemical bonding and metallic bonding
  • Structure and physical properties of ionic substances, covalent substances and metallic substances
  • Differences in the physical and chemical properties of simple molecular structures versus giant molecular structures
  • Differences in the physical and chemical properties of diamond versus graphite

7. Writing Equations

  • Determine the balanced chemical equation or ionic equation for a specific chemical reaction

8. Mole Concept and Chemical Calculations (also known as Mole Calculations)

  • Relative atomic mass, relative molecular mass and relative formula mass
  • Mole and molar mass
  • Empirical and molecular formulae
  • Percentage composition of compounds
  • Molar volume of gases
  • Avogadro’s Constant
  • Concentration of solutions
  • Molar ratio comparison using a balanced chemical equation
  • Limiting and excess reactants
  • Volumetric analysis
  • Percentage yield and percentage purity

9. Acids and Bases

  • Physical and chemical properties of acids
  • Physical and chemical properties of alkalis
  • Strength of acids and alkalis
  • Basicity of acids
  • Role of water in acidity
  • Strength versus concentration
  • The pH Scale
  • Indicators such as litmus and universal indicators
  • How to control the acidity of soil by using quicklime and slaked lime
  • Types of oxides (acidic, basic, neutral and amphoteric oxides) and their properties

10. Salts

  • Solubility of salts
  • Water of crystallisation
  • Anhydrous and hydrated salts
  • Methods of preparation of salts (titration, acid with excess substances, ionic precipitation)

11. Qualitative Analysis (QA)

  • Tests to identify aqueous cations
  • Tests to identify anions
  • Tests to identify gases

12. Redox Reaction (Oxidation and Reduction)

  • Oxidation / reduction in terms of gain / lose of oxygen atoms
  • Oxidation / reduction in terms of gain / loss of hydrogen atoms
  • Oxidation / reduction in terms of gain / loss of electrons
  • Oxidation / reduction in terms of increase / decrease of oxidation states (numbers)
  • Test of oxidising agents using acidified potassium manganate (VII)
  • Test of reducing agents using aqueous potassium iodide

13. Metals and Reactivity Series

  • Properties of pure metals versus alloys
  • Determining the order of reactivity of metals using The Reactivity Series
  • Reaction of metals with H2O
  • Reaction of metals with dilute acid solutions
  • Metal displacement reactions
  • Reduction of metal oxides with hydrogen / carbon
  • Thermal decomposition of Metal Carbonates
  • Methods of extraction of metals
  • Blast Furnace – extraction of iron from haematite
  • Properties and used of the 3 types of steels (mild steel, high carbon steel and stainless steel)
  • Conditions for rusting to occur
  • Rust prevention using barrier method or sacrificial method
  • Advantages and disadvantages of recycling metals

14. Electrolysis

  • Electrolytic cells using aqueous or molten electrolytes and use of inert or reactive electrodes
  • Purification of copper
  • Electroplating
  • Simple cells

15. The Periodic Table

  • Elements are arranged in the order of atomic number (number of protons)
  • Group versus period
  • Metals versus non-metals
  • Metalloids
  • Properties of Group I elements (Alkali Metals) and their trends down the group
  • Properties of Group VII elements (Halogens) and their trends down the group
  • Properties of transition metals
  • Properties of Group 0 elements (Noble Gases)

16. Energy Changes

  • Exothermic Changes versus Endothermic changes
  • Energy level diagram
  • Energy profile diagram and activation energy
  • Bond-breaking and bond-making
  • Combustion of fuels
  • Hydrogen-oxygen fuel cell
  • Advantages and disadvantages of using hydrogen as a fuel

17. Speed of Reaction (also known as Rate of Reaction)

  • Factors affecting the speed of reaction (temperature, concentration of solutions, pressure of gases, surface area of solids and the use of catalysts)
  • Rate graphs
  • Characteristics of a catalyst
  • Catalysts and activation energies
  • Enzymes – biological catalysts

18. Ammonia

  • Reversible reactions
  • How the changes in conditions (temperature, pressure and use of suitable catalyst) will affect the yield and rate of production of ammonia
  • Optimal conditions of the Haber Process – manufacturing of ammonia industrially
  • Displacement of ammonia from ammonium salts

19. Air and The Atmosphere

  • Composition of unpolluted air
  • Air pollutants (sources, adverse effects and how to reduce them)
  • Acid rain (formation, adverse effects and how to reduce them)
  • Catalytic converters
  • Flue gas desulfurisation
  • Depletion of the Ozone Layer
  • Global warming due to greenhouse gases like carbon dioxide and methane
  • Effects of global warming

20. Organic Chemistry

  • Characteristics of a homologous series
  • Fractional distillation of petroleum (also known as crude oil)
  • Uses of the different fractions of crude oil
  • Physical and chemical properties of alkanes
  • Physical and chemical properties of alkenes
  • Isomerism
  • Production of alkenes by cracking
  • Physical and chemical properties of alcohols
  • Physical and chemical properties of carboxylic acids
  • Oxidation of alcohols to respective carboxylic acids
  • Esterification
  • Uses of ethanol
  • Uses of esters
  • Addition and condensation polymerisations

There you go. All the possible topics/concepts you might be tested for Paper 1 MCQ on 15th November 2019. Do study hard for it and aim to score 100% for it.

Now, if you do not know how (or simply too lazy or unmotivated) to revise and prepare for this final MCQ paper, we welcome you to join us in the upcoming annual Score 100% MCQ Workshop. This is the 11th year we are conducting this signature workshop to help students to ace their Chemistry. Let me help you.

Click the image below for more information and sign-up. Seats are extremely limited (5 seats left at the point of writing this blog post). So do take the necessary actions fast!

To Your Chemistry Success,

Sean Chua | Winners Education

PS: A quick note that we will be conducting our Score 100% O-Level Pure Chemistry MCQ Workshop on 9th November 2019 to help students to score full marks for their Paper 1 (MCQ Paper) with 30% weightage. We have consistently received positive feedbacks and glowing reviews for this annual workshop and this will be the 11th consecutive year that we are conducting it. Join us if you are committed to UP your overall Chemistry grade.

“This programme tells me the topics that I am weak in and it emphasises the importance of getting full marks for Chemistry MCQ. I have learnt to manage my time wisely, which is crucial in doing Paper 1 as I usually could not finish the paper. I learnt more about the strategies of doing MCQ and revise on key concepts. I hope I am able to get full marks and I will recommend this to anyone taking O-Levels.” Cher Yi Jia, Nan Hua High School

Tips for O-Level Pure Chemistry Paper 2 Written Exam 2019

WARNING: This is a very lengthy post which covers comprehensively the key concepts for students taking the 2019 O-Level Pure Chemistry (code: 6092) Paper 2 Structured & Free Response. The links in blue when clicked will show the relevant YouTube videos or blog posts and will further reinforce your understanding.

For students based in Singapore, you would have taken the O-Level Pure Chemistry syllabus (code: 6092) Paper 3 Practical Exam on Wednesday 10th October 2019. Hope you benefitted from the Tips for O-Level Pure Chemistry Paper 3 Practical Exam 2019 blog post. Several readers told me that they were glad to have read my previous blogpost as I have reminded them on some of the key concepts which will be tested in practicals (and THEY CAME OUT!).

Most of my students in my Secondary 4 weekly tuition classes found the practical to be easy as the three questions asked were quite basic and straight forward. We even managed to kind of spot some of these common possible tests as we were doing our topical revision.

  • Question 1 was on Acid-Base Neutralisation and Energy Changes (use of thermometer to determine the temperature of solution). Mole calculations was being tested, as usual.
  • Question 2 was on Thermal Decomposition of Sodium Hydrogencarbonate and to find the Percentage by Mass of Sodium Hydrogencarbonate present in an Impure Sample as well as to Identify the Impurity. QA anion tests for chloride, Cl– and sulfate, SO42- ions were involved. Students were also tested on why excess dilute nitric acid must be added before the addition of AgNO3(aq) and Ba(NO3)2(aq) to test for chloride, Cl– and sulfate, SO42- ions respectively. All these were covered comprehensively in our weekly revision tuition classes.
  • Question 3 was on Planning and students were asked to outline a method to obtain crystals of sodium hydrogensulfate using 1.0 mol/dm3 sulfuric acid and aqueous sodium hydroxide of known concentration.

No matter how you have fared for the Practical Paper 3, you need to look forward to the other two papers which makes up the bulk of GCE O-Level Pure Chemistry syllabus. Paper 2 Structured & Free Response and Paper 1 MCQ have a combined 80% weightage. Scoring well in them will still give you a Distinction A-grade, regardless of the Practical Paper 3.

During the lessons in our Sec 4 Pure Chemistry and IP Chemistry tuition classes, I have shared with my students on a 15 pages checklist on the concepts which will be tested.

Today, I would like to share with you, my readers on some of the key concepts (summarised) you may be tested for your upcoming Paper 2 Structured & Free Response Exam on 30th October 2019.

Format of Paper 2 Structured & Free Response Exam:

First of all, we must know that Paper 2 is worth a total of 80 marks and this constitute 50% weightage of your overall Chemistry grade. The time allocated to finish this paper is 1 hour and 45 minutes.

According to Singapore Examinations & Assessment Board (SEAB), this paper consists of two sections.

Section A will carry 50 marks and consists of a variable number of compulsory structured questions.

Section B will carry 30 marks and consists of three questions:

  • The first two questions are compulsory questions, one of which will be a data-based question requiring candidates to interpret, evaluate or solve problems using a stem of information. This question will carry 8–12 marks.
  • The last question will be presented in an either/or form and will carry 10 marks.

A copy of the Periodic Table of Elements will be printed as part of this paper and students should make full use of it.

Key Concepts to be tested:

Listed by topics, students must know the following key concepts well before their Paper 2 Exam.

1) Experimental Techniques

  • suitable apparatus to measure time, temperature, mass and volume
  • suitable apparatus to collect gases and measure rates of reaction

2) Separation Techniques

  • separating techniques such as filtration, chromatography, simple distillation, fractional distillation, separating funnel, crystallisation, evaporation to dryness and sublimation.
  • interpret paper chromatograms including comparison with ‘known’ samples and the use of Rf values
  • use of locating agents in the chromatography of colourless compounds

3) Qualitative Analysis (QA)

  • identification of 8 cations
  • identification of 5 anions
  • identification of 6 gases

NOTE: We might be expecting some more marks in Paper 2 (as well as Paper 1) this year for QA. Do remember the 3 tables of tests! Be prepared!

4) Kinetic Particle Theory

  • changes of states and the energy involved
  • evidence for the movement of particles in liquids and gases
  • explain everyday effects of diffusion in terms of particles
  • effect of molecular mass and temperature on the rate of diffusion

5) Atomic Structure

6) Chemical Bondings and Structural Properties

  • determine the chemical formula of ionic compounds
  • describe the formation of ionic bonds between metals and non-metals, e.g. NaCl; MgCl2
  • state that ionic materials contain a giant lattice in which the ions are held by electrostatic attraction, e.g. NaCl
  • relate the physical properties of ionic compounds to their giant crystal lattice structures
  • determine the chemical formula of covalent molecules
  • describe, using ‘dot-and-cross’ diagrams, the formation of covalent bonds between non-metallic elements, e.g. H2; O2; H2O; CH4; CO2
  • relate the physical properties of covalent substances to their structure and bonding
  • compare the structure of simple molecular substances, e.g. methane; iodine, with those of giant molecular substances, e.g. poly(ethene); sand (silicon dioxide); diamond; graphite in order to deduce their properties
  • compare the bonding and structures of diamond and graphite in order to deduce their properties such as electrical conductivity, lubricating or strength
  • describe metals as a lattice of positive ions in a ‘sea of electrons’
  • relate the electrical conductivity of metals to the presence of mobile electrons in their structures

You may also find my YouTube video on Chemical Bonding Overview useful towards your final revision.

7) Mole Concepts and Chemical Calculations

  • construct chemical equations, with state symbols, including ionic equation
  • define relative atomic mass, Ar
  • define relative molecular mass, Mr
  • calculate relative molecular mass (and relative formula mass) as the sum of relative atomic masses
  • calculate percentage mass of an element in a compound
  • calculate empirical and molecular formulae
  • calculate stoichiometric reacting masses and volumes of gases
  • calculations regarding limiting and excess reactants
  • apply the concept of solution concentration (in mol/dm3 or g/dm3) to process the results of volumetric experiments
  • calculate % yield and % purity

For those who are not strong in writing ionic equations yet, fret not because it is actually very easy to do so. You just have to follow a series of standard steps (at least that’s how all my students learned effectively from me) and you will ALWAYS get the answer. You can watch my YouTube videos on Writing Ionic Equations Part 1 and  Writing Ionic Equations Part 2 to master it.

I also have 2 YouTube videos on solving Mole Calculations Part 1 and Mole Calculations Part 2. You can also do a search in this blog for all the relevant Mole Calculations discussion of exam-based questions.

8) Electrolysis

  1. cations: linked to the metals reactivity series
  2. anions: halides, hydroxides and sulfates e.g. aqueous copper(II) sulfate, dilute sodium chloride solution, etc
  3. concentration effects (as in the electrolysis of concentrated and dilute aqueous sodium chloride)

9) Energy Changes

  • describe the meaning of enthalpy change in terms of exothermic (negative enthalpy change) and endothermic (positive enthalpy change) reactions
  • represent energy changes by energy level diagrams, including reaction enthalpy changes
  • represent energy changes by energy profile diagrams, including reaction enthalpy changes and activation energies
  • describe bond breaking as an endothermic process and bond making as an exothermic process
  • explain overall enthalpy changes in terms of the energy changes associated with the breaking and making of covalent bonds
  • describe hydrogen, derived from electrolysis of water or cracking of hydrocarbons, as a potential fuel, reacting with oxygen to generate electricity directly in a fuel cell i.e. hydrogen-oxygen fuel cell (note that details of the construction and operation of a fuel cell are not required)
  • state the advantages and and disadvantages of hydrogen as an alternative fuel

10) Rate of Reactions

You may find my YouTube video on the 5 Factors that affects the Rate of Reaction useful towards your final revision.

11) Redox Reactions

You may find my blog post on Tests for Oxidising Agents and Reducing Agents useful towards your final revision. Cambridge examiners love to test students on their concepts.

12) Acids & Bases

  • define acid and alkali in terms of the ions they produce in aqueous solution and their effects on Universal Indicator
  • how to test hydrogen ion concentration and hence relative acidity using Universal Indicator and the pH scale
  • difference between strong and weak acids in terms of the extent of ionisation or dissociaton i.e. strength of acids and alkalis
  • basicity of acids
  • chemical properties of acids as in reactions with metals, bases and carbonates
  • uses of sulfuric acid in the manufacture of detergents and fertilisers, and as a battery acid
  • ionic equation for acid-alkali neutralisation is H+(aq) + OH–(aq) → H2O(l)
  • importance of controlling the pH in soils and how excess acidity can be treated using calcium hydroxide
  • chemical properties of bases in reactions with acids and with ammonium salts
  • classify oxides as acidic, basic, amphoteric or neutral based on metallic/non-metallic character as well as state their chemical properties

You may find my YouTube video on Strength versus Basicity of Acids useful towards your final revision. Cambridge examiners love to test students on their concepts.

13) Salts

  • solubility for common salts such as nitrates, chlorides (including silver and lead), sulfates (including barium, calcium and lead), carbonates, hydroxides, salts of Group I cations and ammonium salts
  • 3 methods to prepare salts are (a) Titration (b) Ionic Precipitation (c) Acid + Excess Insoluble Substances
  • describe the techniques used in the preparation, separation and purification of salts

14) Ammonia

  • use of nitrogen (from air) and hydrogen (from the cracking of crude oil) in the manufacture of ammonia
  • essential conditions for the manufacture of ammonia by the Haber process
  • displacement of ammonia from ammonium salts with the use of strong alkalis

You may find my recent blog post on Ammonia and The Haber Process useful towards your final revision. Cambridge examiners love to test students on their concepts.

15) Periodic Table and Group Trends

  • describe the Periodic Table as an arrangement of the elements in the order of increasing proton (atomic) number
  • relationship between group number and the ionic charge of an ion of an element
  • similarities between the elements in the same group of the Periodic Table in terms of their electronic structure
  • change from metallic to non-metallic character from left to right across a period of the Period Table
  • relationship between group number, number of valency electrons and metallic/non-metallic character
  • Group I alkali metals are relatively soft, low density metals showing a trend in melting point and in their reaction with water
  • Group VII halogens are diatomic, non-metals showing a trend in colour, state and their displacement reactions with solutions of other halide ions
  • Group 0 noble gases are monatomic elements that are chemically unreactive (full electronic configuration) and hence important in providing an inert atmosphere industrially, e.g. argon and neon in light bulbs; helium in balloons; argon in the manufacture of steel
  • transition elements are metals having high melting point, high density, variable oxidation state and forms coloured compounds
  • transition elements and/or their compounds are often able to act as catalysts

16) Metals

  • metals have high melting and boiling points, malleable, good conductors of heat and electricity
  • alloys is a mixture of a metal with another element, e.g. brass; stainless steel
  • explain why alloys have different physical properties to their constituent elements (metals)
  • metals reactivity series in terms of decreasing reactivity: potassium > sodium > calcium > magnesium > aluminium > zinc > iron > tin > lead > (hydrogen) > copper > silver > gold
  • understand the reactions, if any, of the metals with water, steam and dilute hydrochloric acid
  • understand the reduction, if any, of their oxides by carbon and/or by hydrogen
  • metal displacement reactions in terms of a more reactive metal to displace a less reactive metal in aqueous solution
  • metal displacement reactions in terms of a more reactive metal to displace a less reactive metal in a metal oxide
  • action of heat on the carbonates of the listed metals and relate thermal stability to the reactivity series
  • ease of extracting metals from their ores by relating the elements to their positions in the reactivity series
  • describe metal ores as a finite resource and hence the need to recycle metals, e.g. recycling of iron
  • discuss the social, economic and environmental issues of recycling metals
  • essential reactions in the extraction of iron using haematite, limestone and coke in the blast furnace
  • describe steels as alloys which are a mixture of iron with carbon or other metals and how controlled use of these additives changes the properties of the iron, e.g. high carbon steels are strong but brittle whereas low carbon steels are softer and more easily shaped
  • uses of mild steel, e.g. car bodies; machinery
  • uses of stainless steel, e.g. chemical plants; cutlery; surgical instruments
  • essential conditions for the corrosion (rusting) of iron are presence of oxygen and water
  • prevent rusting by barrier protection e.g. painting, greasing, plastic coating, galvanising
  • prevent rusting by sacrificial protection e.g. underground water pipes have a piece of magnesium attached to them

17) Air & Atmosphere

  • volume composition of gases present in dry air is approximately 78% nitrogen, 21% oxygen and the remainder being noble gases (with argon as the main constituent) and carbon dioxide
  • name some common atmospheric pollutants, e.g. carbon monoxide; methane; nitrogen oxides (NO and NO2); ozone; sulfur dioxide; unburned hydrocarbons
  • state the sources and adverse effects of these pollutants, as well as how to reduce or prevent them
  • redox reactions in catalytic converters to remove combustion pollutants
  • use of calcium carbonate to reduce the effect of ‘acid rain’ and in flue gas desulfurisation
  • importance of the ozone layer and the problems involved with the depletion of ozone by reaction with chlorine-containing compounds, chlorofluorocarbons (CFCs)
  • describe the carbon cycle in simple terms, to include (a) the processes of combustion, respiration and photosynthesis (b) how the carbon cycle regulates the amount of carbon dioxide in the atmosphere

18) Organic Chemistry

  • natural gas (mainly methane) and petroleum as sources of energy
  • petroleum aka crude oil is a mixture of hydrocarbons and its separation into useful fractions by fractional distillation
  • name the seven fractions in the order of increasing boiling points (petroleum gas, petrol aka gasoline, naphtha, kerosene aka paraffin, diesel oil, lubricating oil, bitumens) and state their uses
  • describe the issues relating to the competing uses of oil as an energy source and as a chemical feedstock
  • an introduction to Organic Chemistry and Organic Compounds
  • homologous series refers to a group of compounds with a general formula, similar chemical properties and showing a gradation in physical properties as a result of increase in the size and mass of the molecules, e.g. melting and boiling points; viscosity; flammability
  • alkanes refers to the homologous series of saturated hydrocarbons with the general formula CnH2n+2
  • draw the structures of branched and unbranched alkanes, C1 to C4, and name the unbranched alkanes methane to butane
  • define isomerism and identify isomers
  • alkanes (exemplified by methane) are generally unreactive but does undergo combustion and substitution reaction by chlorine or bromine in the presence of UV light
  • alkenes refers to the homologous series of unsaturated hydrocarbons with the general formula CnH2n
  • draw the structures of branched and unbranched alkenes, C2 to C4, and name the unbranched alkenes ethene to butene
  • manufacture of short chain alkenes, short chain alkanes and hydrogen by cracking hydrocarbons
  • cracking is essential to match the demand for fractions containing smaller molecules from the refinery process
  • difference between saturated and unsaturated hydrocarbons in terms of their molecular structures
  • test for unsaturation using aqueous bromine
  • alkenes (exemplified by ethene) undergo combustion, addition polymerisation and the addition reactions with bromine, steam and hydrogen
  • meaning of polyunsaturated when applied to food products
  • manufacture of margarine by the addition of hydrogen to unsaturated vegetable oils to form a solid product
  • alcohols refers to the homologous series containing the –OH group with the general formula of CnH2n+1OH
  • draw the structures of alcohols, C1 to C4, and name the unbranched alcohols, methanol to butanol
  • alcohols undergo combustion and oxidation reaction (to form respective carboxylic acids)
  • formation of ethanol by (a) the catalysed addition of steam to ethene known as hydration, and (b) by fermentation of glucose
  • uses of ethanol such as: as a solvent, as a fuel and as a constituent of alcoholic beverages
  • carboxylic acids refers to the homologous series containing the –CO2H group with the general formula of CnH2n+1COOH
  • draw the structures of C1 to C4 carboxylic acids, methanoic acid to butanoic acid, and name them
  • carboxylic acids are weak acids, reacting with carbonates, bases and some metals
  • formation of ethanoic acid by (a) the oxidation of ethanol by atmospheric oxygen or (b) acidified potassium manganate(VII)
  • describe the reaction of a carboxylic acid with an alcohol to form an ester
  • commercial uses of esters such as perfumes, flavourings and as solvents
  • macromolecules are large molecules (also known as polymers) built up from small units known as monomers
  • addition polymer such as poly(ethene) and poly(propene), from their monomers ethene and propene respectively
  • uses of poly(ethene) as typical plastic such as plastic bags, clingfilm and water pipes
  • condensation polymers such as nylon (a polyamide) and Terylene (a polyester)
  • typical uses of man-made fibres such as nylon and Terylene are clothing, curtain materials, fishing line, parachutes and sleeping bags
  • pollution problems caused by the disposal of non-biodegradable plastics e.g. land and air pollution

It is important that students go through all the bullet points stated above (as well as ALL my related YouTube videos) and make sure that they know the Chemistry concepts involved. Do take note of all the necessary keywords and chemical equations too.

Feel free to share this blog post with all your friends who are taking GCE O-Level Pure Chemistry (and IP Chemistry).

I would like to sign off by wishing everyone (my own students as well as those I have not met before) the best in their O-Level Pure Chemistry Paper 2!

PS: A quick note that we will be conducting our Score 100% O-Level Pure Chemistry MCQ Workshop on 9th November 2019 to help students to score full marks for their Paper 1 (MCQ Paper) with 30% weightage. We have consistently received positive feedbacks and glowing reviews for this annual workshop and this will be the 11th consecutive year that we are conducting it. Join us if you are committed to UP your overall Chemistry grade.

To Your Chemistry Success,

Sean Chua | Winners Education

“This programme tells me the topics that I am weak in and it emphasises the importance of getting full marks for Chemistry MCQ. I have learnt to manage my time wisely, which is crucial in doing Paper 1 as I usually could not finish the paper. I learnt more about the strategies of doing MCQ and revise on key concepts. I hope I am able to get full marks and I will recommend this to anyone taking O-Levels.”  Cher Yi Jia, Nan Hua High School

Tips for O-Level Pure Chemistry Paper 3 Practical Exam

Student doing Chemistry Practical in laboratory

Chemical Calculations & Key Sources of Error

It is the time of the year again. GCE O-Level Examination has started in Singapore for academic year with the science practicals.

Students in Singapore who are taking the O-Level Pure Chemistry syllabus (code: 6092) will be taking their Paper 3 Practical Exam on 2 October 2024.

During the last few lessons in our Sec 4 Pure Chemistry and IP Chemistry tuition classes, I have recapped with my students on the key points to take note of for their upcoming Chemistry practical examination.

Today, I would like to share with you readers on some of the key points you should also take note of.

Format of Paper 3 Practical:

First of all, we must know that Paper 3 Practical is worth a total of 40 marks and this constitute 20% weightage of your overall Chemistry grade. The time allocated to finish your practical paper is 1 hour and 50 minutes.

This practical paper consists of a variable number of compulsory practical questions. Students must attempt all the questions and should not skip anyone of them.

One, or more, of the questions will incorporate assessment of Planning (P) and require candidates to apply and integrate theoretical knowledge and understanding from different sections of the Pure Chemistry syllabus.

The assessment may also include questions on data-analysis which do not require practical equipment and apparatus at all. It requires the treatment of given experimental data in drawing relevant conclusion and analysis of proposed plan. As such, students should revise their theory and know their concepts well before going to their practical exam.

Candidates are not allowed to refer to notebooks, textbooks or any other information during the assessment.

A copy of the Notes for Qualitative Analysis will be given to students for reference, which includes the procedures and observations when carrying out tests to test for (1) Cations, (2) Anions and (3) Gases.

[Source: https://www.seab.gov.sg/docs/default-source/national-examinations/syllabus/olevel/2024syllabus/6092_y24_sy.pdf]

Do note that the assessment of Planning (P) will have a weighting of 15% and the rest will have a weighting of 85%.

Assessment of Skills:

According to Singapore Examination Assessment Board (SEAB), you will be assessed in the following skill areas:

(a) Planning (P)

You should be able to:

  • identify key variables for a given question/problem
  • outline an experimental procedure to investigate the question/problem
  • describe how the data should be used in order to reach a conclusion
  • identify the risks of the experiment and state precautions that should be taken to keep risks to a minimum

(b) Manipulation, measurement and observation (MMO)

You should be able to:

  • set up apparatus correctly by following written instructions or diagrams
  • use common laboratory apparatus and techniques to collect data and make observations
  • describe and explain how apparatus and techniques are used correctly
  • make and record accurate observations with good details and measurements to an appropriate degree of precision
  • make appropriate decisions about measurements or observations

(c) Presentation of data and observations (PDO)

You should be able to:

  • present all information in an appropriate form
  • manipulate measurements effectively for analysis
  • present all quantitative data to an appropriate number of decimal places/significant figures

(d) Analysis, conclusions and evaluation (ACE)

You should be able to:

  • analyse and interpret data or observations appropriately in relation to the task
  • draw conclusion(s) from the interpretation of experimental data or observations and underlying principles
  • make predictions based on their data and conclusions
  • identify significant sources of errors and explain how they affect the results
  • state and explain how significant errors may be overcome or reduced, as appropriate, including how experimental procedures may be improved

Topics and Skills to be tested:

Before going to the Chemistry practical exam, you must first be very sure of the type of questions (and thus the hands-on practicals) that you will be tested. You should have some experience by now, based on those Chemistry practicals sessions you went through with your school teachers. Check your practical worksheets to revise.

You must be able to use appropriate apparatus/equipment to record a range of measurements such as mass, length, time, volume and temperature.

In addition, you will be expected to handle a range of experimental techniques such as:

1. Titration

  • acid-base titration (with suitable indicators such as methyl orange, screened methyl orange, and thymolphthalein)
  • other types of titrations may also be required, and where appropriate, sufficient working details will be given

2. Speeds of reaction that may involve measuring of the quantities of products or reactants at regular time intervals

  • measuring the volume of a gas produced
  • measuring the decrease in mass of a reaction mixture
  • measuring the time taken for a precipitate to be formed
  • measuring the time taken for a coloured solution to be decolourised

3. Separation techniques

  • simple paper chromatography
  • crystallisation
  • filtration
  • distillation

4. Preparation of salts

  • titration
  • acids + excess insoluble substances
  • precipitation

5. Gas collection

  • displacement of water
  • downward delivery
  • upward delivery

6. Drying gases with the use of drying agents such as

  • concentrated sulfuric acid
  • quicklime
  • fused calcium chloride

7. Displacement reactions such as

  • metals displacement reaction
  • halogen displacement reaction
  • displacement of ammonia from ammonium salts

8. Tests for oxidising and reducing agents

  • use of acidified potassium manganate (VII) as oxidising agent to test for reducing agent
  • use of aqueous potassium iodide as reducing agent to test for oxidising agent

9. Qualitative Analysis

  • test for the 8 cations
  • test for the 5 anions
  • test for the 6 gases

According to SEAB, you would not be required to carry out physical tests involving Pb2+ ions or sulfur dioxide gas.

Note that reactions involving ions not included in the Notes for Qualitative Analysis may be tested. In such cases, you will not be expected to identify the ions but only to draw conclusions of a general nature.

You should not attempt tests, other than those specified, on substances, except when it is appropriate to test for a gas.

10. Test of simple organic reactions

  • test-tube reactions indicating the presence of unsaturation (C=C)
  • test-tube reactions to test for presence of carboxylic acids

11. Energy changes

  • dissolving of a solid in water
  • reactions between two aqueous solutions such as acid-alkali neutralisation reaction

Procedure to investigate energy changes involving the dissolving of a solid in water would simply be:

  • Measure the temperature of water
  • Add the solid into the water and then stir the mixture
  • Measure the temperature of the water after the solid has completely dissolved in it

12. Dataloggers

You are expected to be familiar with the use of dataloggers. Planning questions may include the appropriate use of data-loggers.

13. Mole concepts & chemical calculations

You may be required to carry out simple calculations as detailed in the theory syllabus. You will be looking at using formulae listed in the topics of mole calculations and energy changes.

Tips on Practical Techniques:

We should also be aware of the accuracy that is expected in titration and general instructions for qualitative analysis.

(a) You should normally record burette readings to the nearest 0.05 cm3 and they should ensure that they have carried out a sufficient number of titrations, e.g. in an experiment with a good end-point, two titres within 0.20 cm3.

(b) In qualitative analysis, you should use approximately 1 cm depth of a solution (1-2 cm3) for each test and add reagents slowly, ensuring good mixing, until no further change is seen. You should indicate at what stage a change occurs. Answers should include details of colour changes and precipitates formed, and the name and test for any gases evolved.

Common Reagents Available:

It is also good to know what are the common chemical reagents which are usually made available for practical exam.

According to SEAB, they are:

  • hydrochloric acid (approximately 1.0 mol / dm3)
  • nitric acid (approximately 1.0 mol / dm3)
  • sulfuric acid (approximately 0.5 mol / dm3)
  • aqueous ammonia (approximately 1.0 mol / dm3)
  • aqueous sodium hydroxide (approximately 1.0 mol / dm3)
  • aqueous barium nitrate (approximately 0.2 mol / dm3)
  • aqueous silver nitrate (approximately 0.05 mol / dm3)
  • limewater (a saturated solution of calcium hydroxide)
  • aqueous potassium manganate(VII) (approximately 0.02 mol / dm3)
  • aqueous potassium iodide (approximately 0.1 mol / dm3)
  • aluminium foil
  • red litmus paper
  • blue litmus paper
  • Universal Indicator paper

For GCE O-Level Pure Chemistry Examination (code: 6092), there will still be Paper 2 (Written Paper) with 50% weightage and Paper 1 (MCQ Paper) with 30% weightage after Paper 3 (Practical Paper). As such, it is important that students continue to revise their theories and concepts all the way until the last paper.

O Level Pure Chemistry Final Exam Boosters

Name of WorkshopDate & TimeVenue
A1: Practical Theory26 & 27 Sep 2024,
6pm to 10pm		Onsite at SMU or Online
A2: The Right Keywords8 & 9 Oct 2024,
6pm to 10pm		Onsite at SMU or Online
A3: Score 100% O Level Pure Chemistry MCQ31 Oct & 1 Nov 2024,
9am to 1pm		Onsite at SMU

Mr Chua told us to draw out the experiment before doing it which I felt is very useful and I’ll definitely do that in the practical. The planning questions were useful and a good consolidation for me to revise. The common mistakes part was very useful because I learnt what I didn’t really understand or was not aware of, and now I still remember those mistakes so I thought it was very useful
Christen Foong, Anderson Secondary School, E8 to A1

“This programme tells me the topics that I am weak in and it emphasises the importance of getting full marks for Chemistry MCQ. I have learnt to manage my time wisely, which is crucial in doing Paper 1 as I usually could not finish the paper. I learnt more about the strategies of doing MCQ and revise on key concepts. I hope I am able to get full marks and I will recommend this to anyone taking O-Levels.”
Cher Yi Jia, Nan Hua High School

To Your Chemistry Success,

Sean Chua