Tips for O-Level Pure Chemistry Paper 3 Practical Exam 2019

Student doing Chemistry Practical in laboratory

It is the time of the year again. GCE O-Level Examination has started in Singapore for academic year 2019 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 10th October 2019.

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/content/syllabus/olevel/2019Syllabus/6092_2019.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.

A quick note that we will be conducting our The Right Keywords Workshop on 16 & 17 October 2019 and Score 100% O-Level Pure Chemistry MCQ Workshop on 9th November 2019 to help students to score full marks for their Paper 2 (Structured Paper) with 50% weighting and 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

To Your Chemistry Success,

Sean Chua

O-Level Chemistry: Ammonia and the Haber Process

Ammonia (NH₃) is a covalent compound and is an extremely useful chemical. It is commonly used to make:

nitrogenous fertilisers which is very important in agriculture
household cleaning agents such as glass window cleaners, floor cleaners, etc
explosives for demolishing buildings and structures

Download & Print Your Chemistry Notes on O-Level Chemistry: Ammonia and the Haber Process here.

Ammonia is manufactured industrially by the Haber Process. We will take a look at the details on this important industrial process later in the blog post.

To learn this topic effectively, we shall structure our discussion into 3 parts, namely:

Part 1: Reversible Reactions
Part 2: Manufacturing of Ammonia by the Haber Process
Part 3: Displacement of Ammonia from Ammonium Salts

Part 1: Reversible Reactions

Many chemical reactions can proceed in one direction only. i.e. they cannot be reversed and they go towards completion. These are known as irreversible reactions.

e.g. Neutralisation reaction between acid and alkali

KOH(aq) + HCl(aq) → KCl(aq) + H₂O(l)

e.g. Combustion reaction

2Mg(s) + O₂(g) → 2MgO(s)

However, some chemical reactions can be reversible. i.e. reactions can go either directions and they reached an equilibrium, instead of going towards completion. These are known as reversible reactions.

At equilibrium, the forward and backward reactions do not stop; they continue, but at the same speed. Hence, there is no overall change in the amounts of reactants and products. A mixture of reactants and products is present and they are known to be in equilibrium.

A double arrow sign, ⇌ is used to indicate a reversible reaction.

Forward reaction refers to the reaction going from left to right.

Backward (or reverse) reaction refers to the reaction going from right to left.

e.g. Thermal decomposition of ammonium chloride, NH₄Cl(s).

In fact, this is a reversible reaction and is represented by the following equation

NH₄Cl(s) ⇌ NH₃(g) + HCl(g)

Upon heating , solid ammonium chloride decomposes to form ammonia gas and hydrogen chloride gas.

Forward reaction: NH₄Cl(s) → NH₃(g) + HCl(g)

Upon cooling, solid ammonium chloride is formed back.

Backward reaction: NH₃(g) + HCl(g) → NH₄Cl(s)

There are many other examples of reversible reactions.

The reaction between nitrogen and hydrogen to form ammonia is another example of a reversible reaction which will be tested in both the GCE O-Level Pure Chemistry Exam as well as IP Year 4 Chemistry Exam.

Part 2: Manufacturing of Ammonia by the Haber Process

Ammonia is manufactured industrially by the Haber Process. The raw materials for the Haber Process are nitrogen gas and hydrogen gas.

Raw Materials:

N₂(g) is obtained from the Fractional Distillation of liquefied air
H₂(g) is obtained from the Cracking of crude oil (petroleum)

Equation:

N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ∆H = -ve

In reversible reactions, the forward and reverse reactions occur simultaneously.

Forward Reaction: N₂(g) + 3H₂(g) → 2NH₃(g)

Backward Reaction: 2NH₃(g) → N₂(g) + 3H₂(g)

Since the reaction is reversible, thus to have a good yield (amount) of ammonia gas, reaction conditions (temperature, pressure and the use of catalysts) are carefully controlled.

Conditions:

The nitrogen and hydrogen molecules are generally unreactive and thus there are no reaction between the two gases are room temperature and pressure.

For the two unreactive gases to react together, a high pressure and relatively high temperature are required. Finely divided iron catalyst is also needed to speed up the chemical reaction.

As we have discussed earlier, the reaction is reversible i.e. some of the ammonia molecules formed will decompose back to become nitrogen and hydrogen molecules. As such, reaction conditions (temperature and pressure) are carefully controlled by chemists and chemical engineers to ensure maximum yield of the product (ammonia gas) at a minimum cost.

1) Effect of Temperature

The lower the temperature, the higher will be the yield of ammonia, since the decomposition of ammonia back to hydrogen and nitrogen will be reduced.

Lower temperature, however, will also results in a slower rate of reaction.

Therefore, there is an optimal temperature that is being used.

2) Effect of Pressure

The higher the pressure, the higher will be the yield of ammonia.

Higher pressure will also increases the rate of reaction.

However, high pressure condition will be dangerous for people working in the manufacturing plant. More expensive equipments must be used to maintain high pressure.

Therefore, there is a limit to the amount of pressure that can be used.

3) Effect of Catalyst

Despite the high pressure and relatively high temperatures being used, the rate of reaction is still quite slow.

Therefore, a suitable catalyst is being used to speed up the rate of reaction.

Optimal Conditions in the Haber Process:

The best conditions used in the industry for obtaining the maximum yield of ammonia at minimum cost are:

Pressure of 200 atm
Temperature of 450 ^oC
Presence of a finely divided iron catalyst

Note:

For students based in Singapore, do note that slightly different values have been quoted for the optimum pressure of the Haber Process, in both the two different Ministry of Education (MOE) approved Chemistry textbooks.

Pearson’s O-Level All About Chemistry reference textbook (2019 Edition) quoted 200 atm.
Marshall Cavendish’s O-Level Chemistry Matters reference textbook (2019 Edition) quoted 250 atm.

Schools will take reference from the approved textbooks so you will see that different GCE O-Level Pure Chemistry and IP Chemistry schools will use either one or the other values. Both are equally acceptable since there is a range of pressures (atm) which is being used industrially.

% Yield Graph

The following % Yield Graph might be given in your upcoming O-Level Pure Chemistry exam or IP Chemistry exam.

Note that you might even be asked to draw a simple graph to see how % Yield of ammonia is related to Temperature and Pressure.

Details in the Haber Process

Nitrogen and hydrogen are mixed in the ratio of 1:3 by volume
Mixture of gases is compressed to 200 atm and heated to 450 ^oC
Mixture of gases are passed over finely divided iron catalyst
Reaction is exothermic
Only about 10-15% of nitrogen is converted to ammonia i.e. % yield = 10-15%
A mixture of nitrogen, hydrogen and ammonia is obtained in the converter
Mixture of gases are then cooled in the cooling chamber (condenser)
Ammonia gas condenses to become liquid ammonia while hydrogen and nitrogen remains as gases
Unreacted hydrogen and nitrogen are pumped back (recycled) into the converter for further reaction.

Part 3: Displacement of Ammonia from Ammonium Salts

Ammonia can also be prepared in the Chemistry laboratory.

When an ammonium salt is heated with a strong alkali such as sodium hydroxide, potassium hydroxide and calcium hydroxide, ammonia gas is being displaced from the salt.

Ammonium Salt + Strong Alkali → Salt + Water + Ammonia

e.g. NH₄Cl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l) + NH₃(g)

Loss of Nitrogen from Fertilisers in Agriculture

Calcium hydroxide and calcium oxide (quicklime) are widely used in agriculture to neutralise excess acidity in soil.

However, both calcium hydroxide and calcium oxide will react with nitrogen fertilisers to form ammonia gas, which then escapes into the atmosphere.

e.g. 2NH₄Cl(aq) + Ca(OH)₂(aq) → CaCl₂(aq) + 2H₂O(l) + 2NH₃(g)

This causes the loss of nitrogen from fertilisers already added to the soil by farmers.

Thus, nitrogenous fertilisers and calcium hydroxide / calcium oxide should not be added to soil at the same time.

YouTube Video Tutorial on Ammonia

You can watch the YouTube Video below to have an even clearer idea about Ammonia.

Click on the following link for the video on O-Level Chemistry . IP Chemistry: Ammonia and The Haber Process

Length of Video: 9.59 minutes

Alright, we have covered everything which is listed in the topic of Ammonia (it is sometimes also known the Nitrogen in the older Chemistry syllabus).

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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Download & Print Your Chemistry Notes Here — **Download & Print Your Chemistry Notes**

O-Level Chemistry: An Introduction to Organic Chemistry

Organic Chemistry by O-Level and IP Chemistry Tuition Class by Sean Chua.

Organic Chemistry is the study of organic compounds.

Organic compounds are compounds which contain the element carbon. Most organic compounds also contain hydrogen. Organic compounds which contain carbon and hydrogen only are known as hydrocarbons.

Organic compounds may also contain other elements such as chlorine, nitrogen, oxygen, etc.

Do note that there are some exceptions. Carbon monoxide (CO), carbon dioxide (CO₂), calcium carbonate (CaCO₃), etc are not classified as organic compounds even though they contain carbon.

In this post, we will look at the following basic fundamentals when it comes to organic chemistry:

Homologous Series
Functional Group
Naming of Organic Compounds
Formulae

A) Homologous Series

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

Do note that some textbooks defined homologous series as a family of organic compounds with the same functional group and similar chemical properties. This sounds a bit off considering that alkanes homologous series does not contain any functional group.

The homologous series covered in GCE O-Level Pure Chemistry syllabus (and other Sec 4 IP Chemistry syllabus) in Singapore are: Alkanes, Alkenes, Alcohols and Carboxylic Acids.

Organic compounds in the same homologous series have the following characteristics:

Represented by a General Formula
Regularly increasing relative molecular masses from one member to the next member
Can be prepared by similar methods
Gradual change in physical properties from one member to the next member
Similar chemical properties
Same functional group (except alkanes homologous series)

B) Functional Group

A functional group is defined as an atom or a group of atoms that gives a molecule its characteristic properties.

All molecules containing the same functional group will behave similarly towards the same chemical reagents, i.e. they have the same chemical properties.

Following are some homologous series and their functional groups that are covered in the Pure Chemistry syllabus:

Alkanes – Do not have any functional groups. There are only C-C and C-H covalent bonds in the molecule.
Alkenes – Contain the carbon-carbon double bond, C=C.
Alcohols – Contain the hydroxyl group, -OH.
Carboxylic acids – Contain the carboxyl group, -COOH.

C) Naming of Organic Compounds

The naming of organic compound is divided into three parts:

Part 1: Length of the parent chain i.e. the number of carbon atoms in the longest continuous (unbroken) chain [also known as the Prefix]

Prefix	meth-	eth-	prop-	but-
Number of carbon atoms in molecule	1	2	3	4

Part 2: Functional Group found in main parent chain [also known as the Suffix]

Homologous series	alkane	alkene	alcohol	carboxylic acid
Suffix	-ane	-ene	-ol	-oic

Part 3: Side group that are attached to the main parent chain [also known as Substituent]

Substituent	-Cl	-Br	-I	-CH₃
Name of side group	chloro	bromo	iodo	methyl

For example, ethene is an alkene with two carbon atoms per molecule.

Ethene - Full Structural Formula — Full Structural Formula of Ethene

For example, propanol is an alcohol with three carbon atoms per molecule.

Propanol - Full Structural Formula — Full Structural Formula of
Propanol

D) Formulae

They are four types of formulae that we can use to represent a particular organic compound. This also means that you will be tested in Chemistry examinations on all four types of formulae which are:

Empirical formula which is the simplest whole no. ratio of atoms of each element
Molecular formula which is the total no. of atoms of each element in each molecule
Structural formula which shows how atoms are arranged in the molecule
Full Structural formula which shows all the bonds between atoms in a molecule

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.

Do stay tuned to the upcoming posts as we will be looking at more key concepts in Organic Chemistry as well as some GCE O-Level Pure Chemistry and Sec 4 IP Chemistry examination questions.

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PS: Under related articles below, there are several blog post discussions and questions related to Organic Chemistry. 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. Consistency is key to master Chemistry.

O Level Pure Chemistry . IP Chemistry June Holidays Intensive Revision Programme

Every year since 2008, our annual Pass With Distinction Revision Workshops for all Sec 3 and Sec 4 O-Level Pure Chemistry, IP Chemistry students have helped many to achieve a breakthrough in their Chemistry.

What is covered during the June Holidays?

The following key topics will be covered in the following workshops:

CM 1: Chemical Bonding

CM 2: Acids, Bases & Preparation of Salts

CM 3: Qualitative Analysis

CM 4: Mole Calculations

CM 5: Rate of Reaction & Energy Changes

CM 6: Redox & Electrolysis

CM 7: Organic Chemistry

“I scored an A1 because you told us that it’s not all about doing practices as much as understanding the subject so I think that built up my foundation of Chemistry and that is what made me feel confident about myself when I was doing the O-Level examinations.”

Bryan Ong

Zhong Hua Secondary School, A1 for O-Level Pure Chemistry

How is the workshop conducted?

Designed into workshops with a focused topic(s) coverage, including key essential concepts, application strategies, relationship linkage, easy-to-remember analogies for understanding abstracts.
Our lessons are delivered in an interactive manner: participants are encouraged to take part in questioning and answering in every workshop. This ensures your child learns effectively within the shortest period of time.

O-Level Chemistry students clarifying doubts with Mr Sean Chua

I’m interested, how can I register?

Please call us at 98287357 for more details.

“She can understand your lesson very well and for the first time, she says she likes Chemistry. Thank you for rekindling her interest in Chemistry. She has also expressed her interest in the weekly class.”

Father of Cher Yi Jia

Nan Hua High School, D7 to A2 in 4 months!

Who is the teacher?

Hi, I am Sean Chua, Chemistry Specialist for O & A – Levels in Winners Education.

Being a full-time professional also means 100% dedication, commitment and responsibility to help your child to unlock his true potential to excel in his Chemistry.
Because of my years of experience and expertise, I have been interviewed by the media such as The Straits Times, My Paper, Today and Shin Min Daily papers to provide my opinions and views on education topics. In addition, we have been contributing articles quarterly in Popular bookstore member’s magazines since 2012 to share our experience on examination preparation tips, studying techniques and changes to Singapore’s education landscape.
Many students and parents know me as the invited author for major books publishers in Singapore and I have written more than five titles of guidebooks, assessment books and Cambridge Ten Year Series (TYS). Most of my Chemistry books are adopted by secondary schools and junior colleges as compulsory or supplementary materials.
My academic website, SimpleChemConcepts.com, has been ranked Number 1 on Google for ‘O Level Chemistry tips’ since 2008. In addition, my collection of over 30 Youtube videos has been widely received by local and international students, parents and teachers. Your child will also be able to benefit from the clear, easy-to-understand and concise explanations, just like thousands of our website and video subscribers.

When parents don’t see improvements in their child’s results despite numerous tuitions, when parents see their child struggling with their Chemistry, when parents understand the importance of seeking professional help to assist their child to improve their confidence and results in Chemistry during the critical O-Level or IP Year 4 period,

I am privileged to be the one they turn to for reliability and effectiveness.

They trust my professionalism in always putting their child’s interest as my utmost priority!

Mrs Sim Testimonial of Winners Education. 4 of her children have been attending our O-Level and A-Level classes since 2016

O-Level Chemistry: Simple Electric Cells

In Electrolytic Cells, electricity is used to produce chemical changes. As such, we say that electrical energy is being converted into chemical energy.

The reverse occurs in Simple Cells (also commonly known as Electric Cells) whereby chemical changes is used to produce electricity i.e. chemical energy is being converted into electrical energy.

Parts of Simple Cells:

A simple cell consists of two solid electrodes placed in an electrolyte connected together by an electrical conductor such as wire.

The two electrodes must be two different metals.

The electrolyte can be acid solution, alkaline solution, salt solution or even a fruit such as orange or lemon.

The voltage produced depends on the positions of the two metals in the reactivity series. The further away the metals are in the reactivity series, the larger will be the voltage.

For example, magnesium/copper electrodes pair will give a larger voltage than zinc/copper electrodes pair.

How does Simple Cells Work?

Let’s use an example of a simple cell to discuss further.

Metal electrode 1: Zinc
Metal electrode 2: Copper
Electrolyte: Dilute NaCl

O-Level Pure Chemistry Tuition class questions, IP Chemistry Electrolysis Dilute NaCl

The metal which is higher up in the metals reactivity series will be preferentially oxidised. It will release electrons more readily and is the negative electrode (known as Anode). In the above example, zinc is more reactive than copper, thus zinc electrode will be the negative electrode.

The electrons leave the zinc electrode and pass through the connecting wires to the copper electrode.

The metal lower down in the metals reactivity series will become the positive electrode (known as Cathode). As such, copper will be the positive electrode. The electrolyte contains positive ions (sodium cations) and hydrogen ions. Hydrogen ions has a higher ease of discharge as compared to sodium ions and will be preferentially discharged (reduced) by accepting electrons from the negative electrode via the wire.

This a a redox reactions whereby oxidation and reduction reactions occurs simultaneously. Electrons is being transferred from zinc atoms to hydrogen ions.

Uses of Simple Cells:

Simple Cells are commonly also known as batteries which provides a portable form of electrical energy. They supply electricity to watches, torches, etc which do not have to connected to the main electricity supply.

YouTube Video Tutorial on Simple cells in Electrolysis

You can watch the YouTube Video below to have an even clearer idea about Simple Cells.

Length of Video: 11.02 minutes

Direct Video Link: https://www.youtube.com/watch?v=MAwJ2wiIBzo

Do understand the difference between Simple Cells and Electrolytic Cells. Every year, I have a large number of students in my O-Level Chemistry Tuition Class and IP Chemistry Tuition Class who told me that they are confused by their school Chemistry teachers and Chemistry tutors with regards to how the two types of cells work. If you have not read my blog posts regarding Electrolytic Cells, you should do a search for them using the search box at the top right hand corner.

I hope you find the content easy for your understanding and that this article will be part of your Chemistry Notes to master Electrolysis topic.

If you have anything valuable to add, leave me a comment below.

Feel free to share this blog post with your friends.

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If you are based in Singapore and needs help with Sec 3 or Sec 4 Chemistry concepts, you can join my weekly O-Level Pure Chemistry and IP Chemistry Tuition Classes.

5 Effective Ways to Prepare for O Level Pure Chemistry and IP Chemistry Even If Your Child Has Been Failing Their Exams

Many parents often asked us: “Is there still time for my child to do well in O Level or IP?” Every June holidays, we receive many phone calls from anxious parents seeking help for their children who didn’t performed well for their mid-year examinations.

We understand their concern. After all, it’s just 4 months before their child sits for the national examination, GCE O Level or their IP examination. Doing well for the O-Level or IP examination gives their child more options to choose from for schools and courses to further their education.

From now till the O Levels, students must stay focused and adopt the correct strategies so as to prepare themselves confidently for the examination. For Chemistry, we suggest the following:

1. Build up Strong Foundation of Basic Concepts

Based on our decades of teaching experience, the root problem we noticed in students underperforming in examination is their lack of understanding of the fundamentals in Chemistry. The level of understanding in the basic concepts is way below par.

Building a strong foundation is the key when students prepare for the O Level Pure Chemistry or IP Chemistry examination, following a topic-by-topic approach. For each topic, students must revise and understand the underlying key concepts or formula, before moving to the next topic.

In Chemistry, it is important to know and master the topics taught in Secondary 3 first. For example, students must have very clear understanding of Secondary 3 basic essential topics such as Chemical Bonding, Writing Balanced Chemical & Ionic Equations, Acids & Bases as well as Mole Calculations. Chemistry is a much more abstract science subject compared to Physics and Biology because almost every topic is interrelated to another topic, especially those covered earlier in Secondary 3.

2. Pay Attention to the Usage of Keywords in Structured Questions

How many of you have your children telling you that they really pay attention in class and can understand what their teachers are teaching?

However, their examination results are dismay and they do not understand why.

This is because just knowing the key concepts i.e. “stories” is not sufficient.They will be marked by the examiners based on the correct keywords or key phrases written.

One of the main challenges that many Chemistry students faced is answering structured questions with the appropriate, specific, complete set of keywords.

For example, the correct keyword for a question could be “Graphite conducts electricity due to mobile electrons” but the common mistake that many students made is “Graphite conducts electricity due to mobile ions”. The reason for such mistake is often rote memorisation without truly understanding the structural properties of graphite and in examination they tend to write the wrong keywords. A-Grade students are able to write the correct keywords as they have their basic concepts to back up their choice of keywords.

Mastery of Chemistry involves strong foundation of basic concepts coupled with clear usage of keywords on top of their application skills.

3. Attempt Ten-Years Series Questions

Next, to put their understanding of each topic to the test, students are advised to start work immediately on the O Level questions as it will provide a reasonable gauge for their level of understanding on key concepts, their level of application skills and build up their confidence at the same time.

Since strong foundation is built on a topic-by-topic approach, the use of the Ten-Years Series (TYS) topical books is strongly recommended, preferably one that provides step-by-step detailed solutions. This allows students to check on the answers at their own convenience.

chemistry tuition class, o-level chemistry revision, ip chemistry tuition class, #1 chemistry tuition singapore, o level chemistry tuition — Do you know A-grade students ask a lot more questions? They think more and do not simply just accept what is taught.

4. Keep Clarifying

Building a strong foundation consists of understanding the key concepts for each topic, testing the student’s understanding by working on the questions, and most importantly, clarifying any doubts and correcting any mistakes made.

Many students accumulate so many doubts over the years that it has reached a critical stage that these doubts, if remained unresolved will cripple their chance of performing well in the
O Level or IP examinations. They must start asking questions to clear their doubts in order to feel confident and prepared!

If your child is afraid of embarrassment, get him to ask someone who has the most up-to-date knowledge in Chemistry concepts and someone he is comfortable with, for example, his friends, his siblings, his teachers or tutors. With technology, he can even email or message his questions to someone he trusts.

Some TYS books even highlight mistakes that are commonly made, and this feature helps students learn how to avoid them during the examination.

5. Examination Strategies

“Know thy self, know thy enemy. A thousand battles, a thousand victories.” – Sun Tzu, The Art of War

Taking examination is just like a game. Your child plays to win within a given time frame, and to win this game, your child must be prepared and aware of the rules of the game. The real opponent is himself.

Once your child has mastered all the key concepts for all the topics, the next step is to learn how to manage his time during the examination. He can attempt a full set of examination papers, under timed condition, to simulate the actual O Level examination. In fact, we put our students through such timed trial exercises in our weekly teachings so that they can understand and appreciate the importance of time management during examination. Through these timed exercises, they can also gain more exposure to a wide variety of questions which will future enhance and challenge their understanding.

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

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