In O Level Chemistry as well as other major Chemistry Examinations such as ICGSE Chemistry, IB Chemistry and IP Chemistry, and A Levels, we have always encounter LIMESTONE – which is essentially Calcium Carbonate CaCO3(s) in the chemical terms.

Do you know we have many natural occurrence of Calcium Carbonate around us?

This picture was taken 3 years ago when i was on holiday in Melbourne, Australia. And the background is the world famous “The Great Ocean Road”. It is a 243 km stretch of road along the south-eastern coast of Australia and provides some of the most scenic coastline in the world, because of its striking and dramatic natural limestone and sandstone rock formations. These formations have been created by erosion from waves and rain and include Loch Ard Gorge, the Grotto, London Bridge (renamed to London Arch after the ‘bridge’ partly collapsed), and most famously the Twelve Apostles (yeah, can you see those spikes formation in the background? It used to be 12th of them, but when i took this photo, there were only 11 left! hmm..wonder how many left now?)

Another Limestone formation – called the “Elephant Rock”

Interesting isn’t it? There are indeed many things (living and non-living things) that are related to Chemistry Theories and Reactions.

Now, as usual, my style! You have seen the nice nice photos and how chemistry is related to our everyday lives (i call it “Chemistry Phenomenon“). TIME to put on your thinking caps to solve some question.

Question:
(i) What will you get when you heat a beaker of Limestone?
(ii) What will you observe?

PS: Leave your suggested answers in “Leave A Reply” below.

PPS: Anyone here from Melbourne or Australia? I would love to hear from you. =)

Chemistry

SPA Tips

Over the last few days, i have received a number of emails and Facebook messages from O Level students for School-Based Science Practical Assessment (SPA) on:

• Possible questions that may be asked in their SPA
• Common errors that they need to be aware of in SPA

I did a check with several schools and found out that this week (9th March – 13th March) is designated as SPA Week for many schools.

SPA is considered as Paper 3 of your O Level Chemistry Examinations and involves a set of teacher-assessed practicals spread over the two/three years of your O Level course. It usually consists of a series of examinable practicals that are spread across your O Level course, with a total of 48 marks – Impt: this makes up 20% of your final O Level Chemistry Examination in terms of weightage.

Since this is a “teacher-based Science Practical Assessments”, the teacher-in-charge will assess students based on the students’ behaviours as well as their experimental techniques in the laboratory (besides your final answers in the practical sheet).

An example of a marking scheme by your teacher-in-charge based on Skill Levels 1 (Easiest) – 4 (Toughest):

Lets check out a potential question on Acids, Bases & Salts from Skill Set 1 (Easiest):

SPA Title: To prepare a soluble salt

Aim: In this experiment you will be assessed on your ability to follow instructions and use apparatus safely

Description:

A soluble crystalline salt can be prepared by the action of a suitable acid on an insoluble metallic oxide or metallic carbonate. The salt can then be purified by crystallisation.

In this experiment, copper(II) sulphate is prepared by the reaction of copper(II) carbonate on dilute sulphuric acid. The equation for this reaction is as follows:

CuCO3 (s) + H2SO4 (aq) –> CuSO4 (aq) + H2O (l) + CO2 (g)

Procedure:

1. Measure out 30 cm3 of sulphuric acid into a beaker.
2. Warm the acid in the beaker until the temperature of the acid is not more than 50 oC.
3. Add the copper carbonate powder to the warm acid, a little at a time, with stirring, until all the acid is used up.
4. Pour the mixture into the filter paper in a filter funnel. Collect the filtrate in an evaporating dish.
5. Evaporate the filtrate. Stop heating when some crystals start to form on the surface of the filtrate or at the side of the dish.
6. Allow the saturated solution to cool slowly.
7. Pour off the liquid from the evaporating dish. Dry the crystals between a few sheets of filter paper.

Marking Scheme:

• Use of appropriate measuring cylinder to measure the volume of the acid.
• Use of appropriate apparatus (glass rod/thermometer but gently) to stir the mixture.
• The hot mixture was poured into the filter paper without spillage/overflow.
• The acid was allowed to cool (check that student reads the temperature of the acid before adding copper (II) carbonate).
• Copper (II) carbonate was added into the beaker, a little at a time, with stirring and without spillage.
• The carbonate was added until no more dissolved/no more bubbles were seen.
• Filtration was properly done (filter paper was folded properly; no prodding of filter paper in funnel; check that filtrate is clear).
• Flame was turned off when the filtrate was saturated (saturation: when crystals appear on the filtrate surface/at the side of the dish).
• Proper control of the flame when filtrate was being evaporated to prevent spluttering. [Safety]
• Goggles were worn. [Safety]

Last & Most Important Tip:

This is a “teacher-based assessment” examinations:

Students: no matter how playful you are – try NOT to STEP onto your teacher’s toe during your SPA period…ssshhhh….hope you get my hint/tip…

Parents: Do remind your child about this important point…

Teachers: Let’s help these students to have a long-lasting interest in Chemistry…

PS: Check out archives (previous blogposts) related to SPA/Chemistry Practicals HERE

PPS: Drop me a message in the “Comments Section” below. I would love to hear from you.

Many of you (Sec 4 and 5) would be taking the GCE O-Level Chemistry Examination this Oct 2009. In your school, your teachers should have gone through 3/5 of the Chemistry Syllabus by now. What you are going to experience next is a fast-pace, adrenaline rushing “chapters-crunching” within the next 3 months, whereby your school teacher will try to finish the rest of the 2/5 syllabus, in order to welcome the Mid-Year Examinations (this exam will show you how much you understand what has been taught for last 2 years).

For those in Sec 3 (2009), you should be studying the chapter on Methods of Purification, Solids/Liquids/Gases or Elements, Compounds & Mixtures,etc. Many of you might wonder what you are studying – some will be “blur like sotong” (in dialect it means “Really Lost”). Many question marks around ???

The basic question many of you would ask me is:

“What really is O-Level Chemistry Examinations?”

“How to Do Well in O-Level Chemistry Examinations?”

My answer to you will be:

It is just a GAME! And in games, you will need to understand the Rules & Regulations (even before you learn the techniques & tactics) in order to do score well within a Time-Period . Sounds like Soccer, Rugby, Baseball, Basketball competitions? Yes..you can equate Sports Competition = GCE O-Level Examinations.

Before we learn the game, the coach will always brief us on the Rules & Regulations, before he steps on his gear to coach you on the Techniques & Tactics.

In O-Level Chemistry Examination, we would first need to know the Rules & Regulations Scheme of Assessments / Arrangement of Chemistry Examination Papers and the time period allowed.

The O-Level Chemistry examination consists of two theory papers and one practical paper:

(click image to see clearly)

Paper 1 consists of 40 compulsory multiple choice questions. Each question carries 1 mark.

Paper 2 consists of two sections:

Section A carries 50 marks and consists of several compulsory structured questions.

Section B carries 30 marks and consists of three questions:

- The 1st two questions are compulsory and have total weightage of 20 marks

- The 3rd question gives you a choice from two questions and carries 10 marks.

Paper 3 is the School-Based Science Practical Assessement (SPA) which involves a set of school-teacher-assessed practicals spread over the two years of your O-Level course.

Note: The marks for each papers are not simply added up. They are weighted (or scaled) to the percentages shown in the table shown above. E.g. the Multiple Choice Paper (Paper 1) is marked out of 40 but contributed 30% of your final O-Level mark.

PS: The above table and discussion is based on Pure Chemistry Syllabus Exam Code 5066. Some students are taking Pure Chemistry Syllabus with other Exam Codes such as 5067, 5068 & 5072. Others may be taking Combine Science (with either Biology or Physics) and have Exam Code such as 5116, 5118, 5152 & 5154). You can check out the Singapore Examinations & Assessment Board (SEAB) website for more specifics, but what’s important is to know the Scheme of Assessment while you prepare for exams.

With these Rules & Regulations of O-Level Chemistry Examination in mind, i will continue with Year 2009 to provide O-Level students with more Chemistry Phenomenons, Tips & Strategies so that you can achieve the score that you truly desire.

Hi everyone,

We had continued where we left off yesterday, on the famous chemistry experiment on Cola + Mentos Mint. In Version 1, we were using the 500ml Normal Coke Classic + Mentos Mint, but the experiment was not so successful due to the CO2 gas being released even before we managed to put in the mentos mint.

Today, in Version 2, we compared the reaction for the following:

Set A: COCA-COLA ZERO + MENTOS MINTS
vs.
Set B: PEPSI MAX + MENTOS MINTS

As in all chemistry experiment, we have tried to keep all parameters/conditions the same:
1. Surrounding Temperature the same
2. Surrounding Pressure the same
3. Volume is the same (both are 1.5L by volume)
4. Equal amount of Mentos Mints were added

PS: Let me know how you feel about this experiment. I would love to hear from you. Simply write your comments in the “Leave A Reply” section below

PPS: If you have a Youtube account, it would be be great if you could give a rating and perhaps some comments of your own.  >> http://www.youtube.com/watch?v=626MFcOx6Lk =)

Hello everyone,

Time for us to talk about Chemistry Phenomenons and Everyday Chemistry in our Lifes.

Have you heard about the reknown COKE + MENTOS Reaction Experiment?

We have decided to carry out this experiment to share with readers on what has been observed.

Something went wrong during the experiment! Haha. Saw it? The experiment did not went so smoothly that i wish. But i will NEVER consider this as a failure. To me, it is just an unsuccessful experiment – cos i will get it RIGHT the next time!

Stay Tuned! We will come back soon with Version 2 of COKE + MENTOS!

PS: What is the reaction that occurs when Mentos is added to Coke? How can i improve this experiment? Drop me a comment or two. I would love to hear from you.

PPS: Rmbr there is no such thing as failures – there is only unsuccessful methods used, unsuccessful methods learned, etc

PPPS: If you did not do well for your recent O Level Chemistry Paper 2, remember you still have Chemistry Paper 1 coming up, worth 40 absolute marks (and 30%!!)

Today’s blogpost we will discuss on some of the important tips for Chemistry Practicals & SPA (School-based Science Practical Assessment) ..In fact, i won’t even call it tips but some crucial things that you would need to take note in Chemistry Practicals.

I received an email enquiry last few days from a local student that is seeking for some “tips for chemistry practicals” for her Pure Chemistry Practical Exams on 9th October and decided to siphon out an hour to share some important points. “Zhiying” – i hope you are in time to read this email before your Chemistry Practical Exams.

Before going to a Chemistry Practical or SPA exams, 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 experiences by now, based on those Chemistry Practicals sessions you went through with your school teachers. Check your Practical Worksheets to revise..

In a Snap-Shot, you will be tested on:

(a) quantitative experiments involving the use of a pipette, burette and an indicator such as methyl orange or screened methyl orange; if titrations other than acid/alkali are set, full instructions and other necessary information will be given;

(b) speeds of reaction;

(c) measurements of temperature based on thermometers with 1°C graduations;

(d) problems of an investigatory nature, possibly including suitable organic compounds;

(e) simple paper chromatography;

(f) filtration;

(g) tests for oxidising and reducing agents as specified in the syllabus;

(h) identification of ions and gases as specified in the syllabus

The question paper will contain notes on qualitative analysis for the use in the examination.
Candidates may also be required to perform simple calculations.

See below for important TIPS on Chemistry Practicals - I have split them into the 2 major tests: Qualitative Analysis & Volumetric Titrations

Common Mistakes: Wrong Observations in Qualitative Analysis (Identification of Ions & Gases)

(a) Some students think there must always be a visible change in every test. In fact, sometimes the examiners want to test you on your “confidence” – nothing happens in some tests and you should record “No Change” or “No Reaction”. It is incorrect to write down changes when you actually see nothing. One Word – Have confidence in yourself!

(b) It is incorrect to state that you observe a “colourless gass” in any experiment. The most you can see is “bubbles of colourless gas”. If not, state some other tests on how you can verify that a certain colourless gas (such as O2, H2 and CO2) is produced.

(c) If you are asked to heat up an unknown substance with sodium hydroxide (NaOH) and Aluminium, don’t assume that ammonia gas (NH3) is the gas given off. It could be hydrogen or other gas. Obtain your answer from your observations and not from memorizing the theory.

(d) Observations on Effervescence are commonly missed out from students. Remember to focus your attention to see if there is an BUBBLES!

(e) When describing solutions, do NOT use the word “clear” when you mean colourless. In chemistry, Clear just means that you can see through it, and the opposite of Cloudy. Use Colourless!

(f) When observing colour changes, make sure that you observe all the colour changes, not just the first and last colours.

&

Common Mistakes: Volumetric Titrations

(a) In volumetric titrations, students are required to repeat the experimental steps until they get at least two consistent results and tick them.

(b) You must average the consistent results that you have ticked, and not all the titration results (cos some maybe off specs/accuracy due to human error)

There are alot more things that you need to pay special attention to in a Chemistry Practical Exam.

Click the archive link HERE (on previous blogposts) to learn more

Until next time (next year i will have the Master Your Chemistry Practicals Guidebook ready- tentative name). Stay tuned if you are taking your major Chemistry Practical Exam next year or so…

Wishing all the best in your Chemistry Practicals Exams,

Sean Chua,
Master Trainer & Author

We learned about Metals & Its Reactivity Series.

Sodium (Na) is considered a very reactive metal and it will reacts vigorously when added into water.

Video below shows the “mini explosions” that occurs when a small piece of sodium is added into a large basin of water.

Alternatively, you can check out this specific link to this youtube video.
http://www.youtube.com/watch?v=6xEyik_dQZI

PS: What is product of this reaction? Leave me a comment below this post.