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
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.
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.
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.
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!
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.
25 cm3 of ammonium hydroxide 1 mol dm-3 is pipetted into a conical flask and few drops of phenolphthalein is added.
A buret is filled with aulphuric acid. Initial burette reading, V1 is recorded.
Sulphuric acid is added into drops by drops into the ammonium hydroxide solution and the content of the conical flask is swirled.
Continue adding sulphuric acid until the colour of phenolphthalein turn to colourless from pink.
Final burette readind, V2 is recorded.
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.
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.
The content is cooled into room temperature and filtered. The crystal (ammonium salt) is dried by using filter paper.
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