*Tips for 2025 O level Chemistry Students

**This article is written by O level Chemistry tutor - Mr Chong. This article is suitable for those in Secondary 3 / 4 and those taking iGCSE.**

Hi all,

 Thank you for viewing this blog for the past months and I welcome you if you are a new viewer. I have closed this post and started a new blog post titled “Tips for 2025 students”

You may just read up on a few of the topics I mention below. The more reading you do, the more confident you are in the O level Chemistry exams. 

It should be a consolation, that your O level exams are likely going be easier than your prelim exams; but this is no time to let down your guard. The most important thing now is to work on your weaknesses and not let the examiners exploit them. My students sometimes beat about the bush but do not answer the questions with the critical key words; so please know what answering style is expected.

Hi, do not worry if you have tuition with me, that I will ask you to read through the below topics. If you are struggling in chemistry, I may only do the basics with you, depending on your needs. I usually assign minimal homework for students.

General Exam Tips:

·        You may want to ask your school teacher(s) or private tutors to provide you with some of the relevant basic A level questions to practice, as the bar for prelims exams and O level papers have been raised.

·         You may also want to go to papacambridge.com to try the international Cambridge papers.




·        You may grab prelim papers from mama shops in your neighborhood shopping areas or Indian shops from Bras Basah complex on the 3rd level. [I do not collect commissions from them.]


·        Do your own concise study notes with visual diagrams and mind-maps.

·        Also, at least one of the sciences (chemistry, biology, physics) papers will be tough. So be prepared!

·        Cambridge seems to favor fertilizers in recent year international papers so that’s one area to visit. 

·         Learn how spell chemical terms correctly

·        Make sure your handwriting is legible. Make the examiners happy who are marking your scripts during Christmas and New Year.

·        Be prepared for surprising and atypical questions in all your papers. 

·        Be as clear as possible when you answer your questions

Areas that may need a little reading

·        You may want to give global warming related questions a brief visit, pay attention to chlorofluorocarbons (CFCs), ozone hole, carbon cycle.

·        Many students are confused about reducing and oxidizing agents, so it may benefit you to take a look.

·        Please do not be confused with the Qualitative Analysis tests for oxygen and hydrogen gases.

·        Those who are confident in your revision, you may like to ask your tutor, if you have one, to teach you about equilibrium, and LE CHATELIER'S principle. This was in the old O level chemistry syllabus, and some examiners like vintage questions.

·        The topics that are slightly more likely to appear in the long structured questions are as follows:

               electrolysis, air and atmosphere, organic chemistry, a little chemical bonding, rates of reaction.

·        For those who have secured their basics, you may want to read up on A level topics such as Energy changes (Energetics in A levels), Periodic Table (Periodicity in A levels), Mole Concept and Redox chemistry.

·        Cambridge may still like mole concept. Also, at least 4 MCQs and a few structured questions may be from organic chemistry.

·        You may like to revise ionic radii, atomic radii, properties of Period 3 elements, all covered in Periodicity chapter. 

·        For chemical bonding, you may like to read up on hydrogen bonding in molecules of water, ammonia etc... 

·        Do not neglect the 1st few chapters of chemistry. There was one year of exam papers where almost 10 marks of a long structured question were devoted to separation techniques in the chemistry lab. 

·        Chemical Bonding is a very important chapter! Make sure you master this chapter! It is 95% almost sure to appear in prelims and GCE exams. 

·         Just in case you have not remembered the solubility table (list of soluble and insoluble salts), please try to commit it to memory soon. It is a very important table that has many applications throughout many chapters of chemistry

·         Do you know about biodiesel fuels, bio-hydrogen and biogas? These links will provide a little information.

·        http://en.wikipedia.org/wiki/Biodiesel#Biodiesel_feedstocks 

·        http://en.wikipedia.org/wiki/Biogas

·        http://en.wikipedia.org/wiki/Biohydrogen 

Just a little Chemistry

Ammonia

Do you know that you should not name NH₃ (aq) as ammonium hydroxide?  Aqueous ammonia in solution exists mainly as ammonia molecules surrounded by water molecules, and little hydroxide ions are formed. That is why aqueous ammonia is known as a weak alkali with a pH of about 9. 

Try completing the equilibrium equation:
NH₃ (aq) + H₂O <==>   _______+ ____________

Potassium Iodide

 Almost all my students were tricked by my "simple" question: what is the color of potassium iodide solution? Some said brown. The answer is that potassium iodide, KI (aq), is colorless.
Potassium iodide is analogous to sodium chloride solution. Potassium and sodium ions belong to Group I ions. Iodide and chloride ions belong to Group VII halide ions. Since sodium chloride solution is colorless, so also potassium iodide is a colorless solution.
Iodine solution (aqueous) is brown in color, usually with some black precipitate of iodine.

Organic Chemistry

·        Students sometimes draw carbon atom with 3 or 5 bonds in them (carbon atom should always form 4 bonds).

·        You should also learn about the polymerization of amino acids, which is related to the chapter on macromolecules

·        You may try drawing an addition polymer or repeating units for example Butene.

·        Do you know the 4 most common giant covalent substances? 

·        Do you know how to distinguish between an alkene and an alkane? What is the test for it? 

·        Do you know the formula of Terylene and Nylon? 

·        Do you know that in organic chemistry,  HO-CH2-CH2-CH2-OH is oxidized by acidified potassium manganate(vii) solution with heating to HOOC-CH2-COOH? Do you know the chemical formula of potassium dichromate (VI), and potassium manganate (VII)? 

·        You may be asked you to name esters in the prelim exams.

·        Fermentation of glucose to form ethanol is an important process. It may come out in prelims, mock prelims, or post-prelims exercises, or even in GCE chemistry exams.

·        There are many reaction conditions, reagents and catalysts in the section of organic chemistry. Understand this section first and then remember the reaction conditions. 

Inorganic Chemistry

·        You need to know the observations when aluminum, lead or zinc ions are added separately with aqueous sodium hydroxide and in excess. 

·        What is the color of copper metal, Iron (II) sulfate, Iron (III) Sulfate, Bromine? 

·        Almost all my students are weak in the topic of identification of ions (test for CATIONS, ANIONS and gases) .You need to study this chapter but it does not appear every year in Paper 2. You can try using some mnemonics to remembering the tests for CATIONS and ANIONS. 

·        You may want to be familiar with the ions HSO₄^-, HCO₃^-, H₂PO₄^-, HPO₄^2-, ClO^-, ClO₃^-. You may want to go to wikipedia on acid and alkaline salts. Do you know that not all salts are neutral?

Thermodynamics

In an endothermic reaction, does the temperature increase/decrease in the reaction mixture?

Electrochemistry

·        Do you know the difference between an electrolytic cell and a galvanic cell? 

·        Take a look at lead-acid battery and nickel type battery in the chapter on electrolysis and electrolytic cell. 

·        You may want to take note of fuel cell questions, either of hydrogen/oxygen or methanol types. You can find the questions from prelim papers 2018.

Chemistry Multiple Choice Questions

Please do not underestimate chemistry MCQ. It constitutes a hefty 30% of the marks amongst all papers. You should try to minimize mistakes, some questions may be tricky so please be careful and read the question carefully.

  

You may like to:

·        Grab hold of C S Toh's A level Chemistry study guide (may be out of stock in bookshops), or - ask your teacher / tutor to teach some basic A level concepts. You can visit your library or National Library in Victoria Street to consult reference books. - go to www.chemguide.co.uk 

N.B.  I am releasing my O Level Pure Chemistry summary notes of *all* Chemistry topics at only S$1.49, offer good only for Singapore students and parents!

 8 Sec 3 and 4 topics with pdf notes are thrown in as bonus!

Transactions are done through e-mail and payment by ATM banking or by PayNow!. I can give you a preview to the notes through e-mail. The notes are useful for exam revision, especially at Sec 4.

Link is here for the preview.

Please e-mail me at chemguide8@hotmail.com

Combined Science students may also use the notes.

Other recommended texts

Please note that I am not earning commissions from the publishers and or the bookshops.

1.      Perfect Guide - Chemistry By Tan Yin Toon. It is very well written and it is more optimized for learning, application and memory association than the textbooks. 

2. Pass with Distinction - Chemistry (By Topic)

****** Also, these are some of the latest recommended textbooks for Cambridge International Exams. They contain many many clues!
http://www.cie.org.uk/news/features/detail?feature_id=44796&utm_source=twitterfeed&utm_medium=twitter
http://www.cambridgestudents.org.uk/subjectpages/chemistry/OLevel/
http://www.cie.org.uk/qualifications/academic/middlesec/olevel/subject?assdef_id=901&view=reslst

Also, here are some topics / questions you can explore:
- emulsions
- hard water
- Do you know the catalysts for the decomposition of hydrogen peroxide? (Chapter on Speed of Reaction)
- Copper (I) salts
- Extraction of zinc from zinc ore
- you may like to scan through the A level notes for chemical bonding. I am not sure if Cambridge may test on some  elementary A level stuff which is simplified to assessment in O level assessment
- Mole Concept calculations are really important; quite a few questions came out in 2011 O level Chemistry exams.       Make sure you master this chapter.
- Are all salts of neutral pH?
- What are acid salts?
- How does pH change when a strong acid is titrated with a strong alkali? *** Important for all students
 - How do conductivity and temperature change when a strong acid is titrated with a strong alkali?
- How does phosphoric acid react with aqueous sodium hydroxide? How does the pH curve look like?
- How does the conductivity change when a precipitate is obtained from 2 aqueous solutions?
- What is C60? What is (buck minister fullerene)? What are carbon nanotubes? How about graphene?
- What is carbon neutrality? What is carbon footprint? What is the carbon cycle?
-  Do you know about CFCs? (Chlorofluorocarbons)
- Do you know about global warming?
- Do you know the reactions that happen inside a catalytic converter of a car?
- What is green chemistry? (A new topic introduced in other UK exam boards)
- What is reverse osmosis? How is water treated? What is NE Water?
- What is a disproportionation reaction? (Redox chemistry)
- What is a clock reaction? (Speed of reaction; may be important in Practical) Speed of  reaction comes out frequently in exams.
- What are organic solvents? What are chloroform, ether, alcohol, cyclohexane? Are organic molecules soluble in organic solvents?
-  What are Cycloalkanes, alkynes, benzene, ketones, aldehydes, amines and amino acids? What are their general formulae? (Organic chemistry)
- Do you know how to write the chemical formula of calcium ethanoate (calcium hydroxide reacting with ethanoic acid)? How is it formed?
- Are silicon carbide (SiC), Boron nitride (BN), Silicon, Silicon dioxide giant molecular, giant molecular layered or simple molecular (simple covalent) substances?



- Do you know how to draw an addition or condensation polymer given its monomer? What about the reverse thinking process? If you are given the formula of a polymer, do you know how to draw its monomer?

Please note that organic chemistry may take up a larger percentage of marks in this year's papers. This section is highly important in exams.

Preparation Tips

·        My advice for exam preparation is not to study throughout the night. Sufficient sleep is needed and since many papers are in the morning, sleeping late can disrupt your sleep cycle and metabolic cycles (and of course biochemical reactions in your body) and you will need a highly alert and clear mind to tackle the novel questions in many subjects.

·        Keep yourself healthy. A little run or gym during the exam period may do wonders. Have a diet more of vegetables and fruits and less fast food.

May the blessings of God be with you. God bless you richly. You CAN do it!

Mr Chong

ex-MOE teacher 

B.Sc(Hons), Diploma in Education (PGDE)

Current Private Chemistry Tutor 

# Mr Chong is not responsible for any inaccuracies or the topics he highlighted that do not appear in assessments. Chemistry knowledge is vast and examiners have a large scope to test for in exam papers.