Paper 3 Trial SBP Year 2009

I'm marking paper 3 of my students now.  So far, students seems not to have much problems in this paper. Average of 5C students score 38/50.  Hopefully the rest of the students would perform too.

Will write more what I notice in the students' answers once I finish marking all the papers. 

This paper touch on

1. Electrochemical series
2. Effect of temperature on the rate of reaction

I suggest all form 4 students to try to answer the first question(Electrochemical Series) of this paper before you sit for your finals exam.  It'll help you to have a better idea about the format of the question from Paper 3. To view the question, please click.

Councils to Recycle Used Cooking Oil

I have seen one group of students did a research to preapre soap by using used cooking oil few years back. The ideas popped in these groups of students as they noticed most of the used cooking oil were not handled properly and passed into drains.  This could lead to environmental problems.

Now, 2 councils in Selangor are about to start to collect used cooking oil from restaurants.  The used cooking oil can be reprocessed to become bio-fuel and bitumen.  Good approach!! For more details, read Councils to recycle used cooking oil from The Star.

Effectiveness of a Fertiliser

Fertilisers are chemicals widely used to increase the yield of fruit or plant. Ammonium fertilisers are inorganic ferlilizer, mainly consists of simple chemical and minerals. Most ammonium ferlisers provide major plant nutrients : nitrogen, phosphorus and potassium(NPK). 

Once added into soil, ammonium ferlisers which consists of ammonium ions are converted to nitrate ions by bacteria. Nitrate ions are absorved by plant roots.  Nitrogen is used to make proteins in stalks and leavers.

Ionic Compound vs Covalent Compound

I found students quite confused over these basic concepts, even though I have shown them computer simulation, diagrams, etc.

Ionic Compound consists of ions.

• Positively charged ions and negatively charged ions are attracted by strong electrostatic force/ionic bond.

Covalent Compound consists of molecules.

• Molecules are attracted by weak intermolecular force/van der Waals force.

Therefore, ionic compound

• has high melting and boiling point
• can conduct electricity in molten state or aqueus solution.  WHY?

Covalent compound

• has low melting and boiling point
• cannot conduct electricity in all state. WHY?

Paper 2 Trial SBP Year 2009

I have finished marking paper 2 of my students. Overall I noticed students had some misconceptions in certain topics like ionic compound vs covalent compound, collision theory.They found the question tricky and made lots of silly mistakes here and there, especially Question 5, 6, 9 and 10. The topics tested in each question are as follows:

Section A
Question 1 : Soap & Detergent; Food additives
Question 2 : Atomic Structure, Isotope, Heating and cooling curve
Question 3 : Determining of empirical formula
Question 4 : Preparation of soluble salt and insoluble salt
Question 5 : Carbon Compounds
Question 6 : Redox reaction in the transfer of electron at a distance and displacement of halogen

Section B:
Question 7 : Alloy and Contact Process
Question 8 : Ionic Compound and Covalent Compound

Section C
Question 9 : Rate of reaction
Question 10 : Energy Profile Diagram and Heat of Combustion

I wish my students can review their mistakes carefully in this paper. Revise those topic that you're still weak for example: numerical problems related to the moles, rate of reaction, carbon compounds, redox, thermochemistry. and avoid careless mistakes during examination. All the best in the coming Trial JPWP!

Form 4 August Holidays Assignment Part 2

This holiday assignment focuses on two main topics in Chapter 9, Manufacture Substance in Industry: Sulphuric Acid and Ammonia.

These two chemicals are ranked among the top products in chemical industry. Sulphuric acid and ammonia are widely used in many aspects and at the same time bring some side effects to the environment.

Hope you'll refer the guide given and explore the topic deeper...

Any comments, just write under this post, ok?

Preparation of Ammonium Fertiliser

Ammonium fertiliser is a type of salt. It can be prepared through a reaction of ammonium hydroxide solution and acid.

 

ammonium hydroxide + acid --> ammonium fertiliser  + water

 

For example, to prepare ammonium sulphate, reactants required are ammonium hdyroxide solution and sulphuric acid.

 

Method used to prepare ammonium sulphate in the laboratory is using titration method.

1. 25 cm³ of ammonium hydroxide 1 mol dm^-3 is pipetted into a conical flask and few drops of phenolphthalein is added.
2. A buret is filled with aulphuric acid. Initial burette reading, V₁ is recorded.
3. Sulphuric acid is added into drops by drops into the ammonium hydroxide solution and the content of the conical flask is swirled.
4. Continue adding sulphuric acid until the colour of phenolphthalein turn to colourless from pink.
5. Final burette readind, V₂ is recorded.
6. Steps 1 - 5 is repeated by adding (V₂- V₁) cm³ of sulphuric acid from the burette into 25 cm³ of ammonium hydroxide solution in the conical flask(with adding phenolphthalein) and the conical flask is swirled.
7. The content of the conical flask is then poured into an evaporating dish and heated until the volume become one third from the initial volume.
8. The content is cooled into room temperature and filtered. The crystal (ammonium salt) is dried by using filter paper.

Diagram to show the set-up of apparatus.

Trial SBP Chemistry Year 2009

Paper 1

Paper 2

Paper 3

Answer Scheme

You are welcomed to post comments here about any problems in this set of question papers..

*Photo taken in Bali, Indonesia.

Physical Properties of the Halogens

Trial Perlis Chemistry SPM Year 2009

Paper 1, 2, 3 and the answer scheme.

Click here to open the pdf file.

For the things we have to learn before we can do them, we learn by doing them. ~Aristotle~

*Picture taken at Sg Lembing, Kuantan.

Chemistry Trial SBP Year 2008

Paper 1

Paper 2

Paper 3

Answer Scheme

Six die of ammonia poisoning

Six die of ammonia poisoning at Tanjung Karang, Selangor.

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Lightweight Reinforced Concrete(LRC)

Lightweight Reinforced Concrete(LRC) is actually one type of composite materials. It is a mixture of polystyrene and concrete. As it is light and cheaper, it is widely used in the construction of buildings.

*Picture taken from SinChew Jit Poh 10 August 2009

Electroplating A Coin with Copper

Yesterday when I entered my chemistry class, I challenged my students to electroplate their key chains/coins with copper before leaving chemistry laboratory at the end of my lessons.

Throughout the lessons, everybody paid 100% attention. By the time they started working in groups, they started talking profesionally.

"use the coin as cathode"

"copper is connected to the positive terminal"

"Wow, teacher, come and have a look! Changes occur so fast!"

"TEAcheer, how does it happen?"

"The coin is so nice!!!!"

This is the product prepared by Diyana. She said she wants to show it to his dad.

I really enjoyed the lesson especially looking them leaving the lab with happy smiling face! Hope everyone realise the importance of electrolysis in their daily life!

Chemical equation that shows the reaction occurs

at anode : Cu ---> Cu²⁺ + 2e^-

at cathode : Cu²⁺ + 2e^- --> Cu

The First Battery

Types of battery available:

1. dry cell
2. alkaline cell
3. mercury cell(e.g. battery in watch, calculator)
4. lead acid accumulator(e.g. car battery)
5. nickel-cadmium cell(e.g. rechargable battery mostly used in camera)
6. lithium ion cell(e.g. laptop, iPod)