2009-12-26

Red Cabbage Juice as An Acid Base Indicator



Have you ever tried this red cabbage(Brassica oleracea var. capitata f. rubra) before? It's often used for salads. Some of friends do not dare to tried even a small piece of it because of its colour.

The cabbage is red/purple, due to the presence of a colour pigment called anthocyanin. Its colour depends at the pH value of the soil. 

More acidic soil, the leaves grow more reddish.
More alkaline soil, more greenish yellow cabbage is produced.

Due to this special characteristic, red cabbage juice can be used as a home made acid base indicator. For more details, please visit http://www.funsci.com/fun3_en/acids/acids.htm.

Try to look around your garden too. May be you can colloect some flower petals and test whether there is any colour when difference acidic/alkaline substances are added. Who knows you might discover your own natural indicator too! Please don't forget to share with me your new finding too!!!

2009-12-25

Predict the Product of Electrolysis of Aqueous Solution

Most students are having a big problem in electrochemistry.  Normally questions related to electrolysis of aqueous solution are their common mistakes.

This is one of the questions in Chemistry SPM 2009 Paper 2.

If you need guide to predict the product of electrolysis of aqueous solution, click here.

You're welcomed to email your answer to sweemoi@gmail.com.  I'll reply and give comments as soon as possible.

2009-12-23

Rate of Reaction between Zinc and Hydrochloric Acid



This video shows the reaction between zinc and hydrochloric acid.  Hydrogen gas is released in both conic flasks.

Points to ponder:
  1. Any possible reasons that contribute the different size of ballons in both experiments?
  2. How to measure the of rate of reaction?

2009-12-18

Relationship Between Concentration of Acid and pH Value



This question appeared in Negeri Sembilan Trial paper. Those students from this state are very lucky.

Some students said they didn't carry out this experiment in their chemistry laboratory. Thus they have no idea how the experiment plan should be.

To my dear current form 4 students, Let's discuss this question together.

2009-12-15

Common Chemicals

Common salt - sodium chloride
Table Sugar - sucrose
Vinegar - ethanoic acid
Vitamin C - ascorbic acid
Baking soda - sodium bicarbonate
Dry ice - solid carbon dioxide
Aluminium foil - aluminium
Copper wire - copper
Clean sand - silicon dioxide
Diamond - carbon crystal

2009-12-08

SPM 2009 Paper 1, 2 & 3

Paper 2
  1. Alloy
  2. Period 2 & formation of ionic bond
  3. Empirical formula of copper oxide
  4. Homologous series, chemical properties of alkene
  5. Rate of reaction, collison theory
  6. Heat of neutralisation
  7. Homologous series, empirical formula & molecular formula & isomerism
  8. Electrochemical series based on potential difference, factor of concentration towards the producf of electrolysis of an aqueus solution
  9. Redox reaction involving changing iron(III) ion to iron(II) ion, U tube
  10. numerical problems involving molarity, role of water on the properties of acid, confirmatory test of cation and anion in a sample of salt given
Paper 3
  1. Electrolytic cell: study how the type of electrode affect the product of electrolysis of copper(II) sulphate solution
  2. Rate of reaction between marble chip and acid
  3. Relationship between the concentration of acid and pH value.  A look at the question.
Paper 1
 
  I notice some blogs already uploaded with the answer. May be you all can have a look. Click here.

2009-12-02

Chemistry Related Career

   One day, one of my students came to approach me after the end of her chemistry lesson.
    "Teacher, is it good I further study in chemistry?" She asked.

   "Of course, yes! But which part of chemistry do you like the most?" I said.

   She started to fall into a deep thought.

   Actually, deep in my heart, I'm glad my students have interest and plan to study more about chemistry.

  There are many fields requires chemistry knowledge:

  1. food science
  2. forensic science
  3. environmental science
  4. oceanology
  5. geochemistry
  6. education(teacher, or lecturer)
  7. biotechnology
  8. medicine
  9. engineering
  10. plastic chemistry
  11. metallurgy
  12. agrochemistry
  13. pharmaceuticals
  14. dietian

  The list is incomplete. Chemistry works in any industrial, educational, scientific, or governmental field. A chemistry student is equipped with excellent analytical and mathematical skills which help them to solve problems in their job.


  Perhaps I'll post more chemistry related career later. So, what's your choice?

 For further reading, you might visit American Chemical Society.

2009-11-26

What are Soap and Detergent?

Most of my students are wondering how to identify soap and detergents? In fact, it's not easy to identify through their physical properties.  Soap and detergent are different in term of their chemical structures and their chemicals required during preparation. Hopefully the slideshow below will help you to to have a better idea.

Soap and Detergents

View more documents from sweemoi khor.

2009-11-24

What's in your food?

I find this book particular interesting. The author, Chia Joo Suan who is a food chemist give us a closer look at food through comprehensive and easy-to- read guide.

Food is important. We consumer food not only to sustain our life but also for their taste, nutritional and medicinal values. Are the food we are taking safe? Many food additives are added to enhance food quality. Do we realize what are they? Do these food additives bring any side effects to our health in the long term?

2009-11-23

Chemicals for Consumer

The discovery of chemicals manufactured for consumers such as cleaning agents, food additives and medicines has helped us improve our health and standard of living. Today, different type of these chemicals are produced to meet the needs and preferences of consumers. Therefore, understanding the chemistry of these chemicals will help a consumer select and use them wisely.

Hopefull this holiday assignment will make you realise the importance of many chemicals available in your daily life.  Any doubt, don't be hesitate to ask. Enjoy your holidays!

2009-11-21

Chemistry Review 2009

   The 2009 School Year at last comes to the end.  This is the first year I teach in this school.  5C, 5F, 4D & 4E were my students . At first, I found it was a whole new experience to teach in a all girls school.  Anyhow, I like my girls and happy with the their effort in their chemistry class.

  But i'm curious. Do my students like their chemistry lesson with me? What do they think about my teaching strategy/approach?  Knowing my students better would help me to improve in the coming school year.

I wish my students could email me their opinion to me, sweemoi@gmail.com. The follows are some guides what you could write:

  1. Do you like your chemistry lesson?
  2. What activity in the class you like the most? Computer simulation of abstract concepts, group experiment, module, topical questions, answering tips, pair/group discussion?
  3. What are your suggestion to improve your chemistry lesson?
  4. How frequent do you visit this blog? Everyday?
  5. Which part in this blog do you like? Notes, tips, class activity, chemistry related website link, chemitry related knowledge?

2009-11-08

How to get prepared for Paper 3 Chemistry SPM?


Many of my students keep on asking me about how to score Paper 3.  They are not sure whether they are ready for it or they are applying the correct learning strategies...

I think the most important is to get to know the format of Paper 3 first.

Different scientific skills are evaluated in this paper:
  1. observing
  2. classifying
  3. measuring and using numbers
  4. inferring
  5. predicting
  6. communicating
  7. using space-time relationship
  8. interpering data
  9. defining operationally
  10. controlling variables
  11. hypothesizing
  12. planning an experiment(problem stat/ement/aim of experiment, hypothesis/variables, materials & apparatus, procedure and tabulation of data)
   The scientifil skils are acquired by the students slowly when they plan, carry out experiments and make a report in their class.  PEKA is another way of assessment to evaluate students' scientific skills and attitudes too.
 
  So, the best strategy I would suggest is to go through the above list and identify which one you are still weak in.  Go through the past year questions or trial question from different state and try to study why an answer for a particular skill is considered as excellent answer(Score 3).

All the best! All the SPM 2009 Candidates.

Volume of Gas



1 mol of any gases, as you name it, oxygen gas, helium gas, hydrogen gas, neon gas, etc.... occupy the same volume in the room condition.

This concept is known as molar volume at room condition, which is 24 dm3 mol-1.

2009-11-04

Question Analysis of Paper 3 Trial Chemistry 2009 from Different State

I have done some analysis on the questions from all the trial papers that I  have gathered. It seems that some  questions are quite popular. However, I haven't get trial papers from Penang and Sarawak.

Hopefully this analysis will help students who are trying their best effort before sitting the Chemistry paper on 8 Dec 2009

2009-10-31

Measuring

Measuring is one of the important skill in chemistry. In the chemistry laboratory, it's common to find various apparatus e.g.buretthe, stop watch, voltmeter, thermomether, etc.

Measuring is one of the scientific skill included in Paper 3 Chemistry SPM. After going through different exam papers, examples of apparatus that I have noticed are as follows:
  • stop watch(2003, 2008)
  • Ruler (2003)
  • Electronic balance(2004)
  • Thermometer(2005, 2006, 2007)
  • Buret
  • Voltmeter
In order to score in this section, remember :
  • write the value of the measurement according to the accuracy of the apparatus. E.g. buretthe reading has 2 decimal places.
  • All the values must be consistent and with units.E.g. the unit for buretthe reading is cm3. Please ensure all reading recorded with 2 decimal places.
Any doubts with the measurement, please leave your comments here. All the best!

2009-10-18

Question Analysis for Paper 2 & Paper 3 Trial SPM 2019 from Different States

Thousands thanks to
  • Hanna & Hanni who have contributed their analysis for Trial Kelantan paper.
  • Dhiya who has sent her analysis for Trial Negeri Sembilan paper
  • Anis Adibah who has comments on Trial Perlis paper. (Incomplete analysis on Paper 2)
  • Syafiqah, Nazirah and Shakina who have posted their comments on Trial Kedah paper
  • Liyana Yahaya and Rohiza comment on Mallaca Trial Paper
  • Sofea and Syazwani  comment on Selangor Trial Paper
  • Lisa and Najihah sent their comments on Perak Trial Paper.
The analysis will be updated from time to time...

2009-10-17

Transfer of Electron at A Distance

Students find difficulties in answering question related to this topic.
  • which electrode is the negative terminal/positive terminal?
  • mark the flow of electrons on the circuit
  • which one is the oxidized substsance/releases electron/reducing agent?
  • which one is the reduced substance/gain electron/oxizing agent.
  • write half equation to show the reaction occur at each electrode
  • write overall ionic equation for the reaction that occur in the U-tube
  • Write observation.

Actually a student only need to remember some examples of oxidizing agent and reducing agent. Some examples of oxidizing agent and reducing agent are as follows

Lets take an examples when iron(II) sulphate solution and bromine water are used.

iron(II) sulphate solution is the reducing agent.

  • iron(II) ion loses electron to form iron(III) ion.
  • So, iron(II) ion is the oxidized substance.
  • As electrons is produced, the electrode that dipped in the iron(II) sulphate solution is negative terminal
  • electrons flow from this eletrode to another one through the external circuit.
  • Observation: the green iron(II) sulphate solution turn yellow/brown
  • Half equation: Fe2+ --> Fe3+ + e-


Bromine water is the oxizing agent.
  • electrode that dipped in bromine receive electron from the external circuit.
  • So, this electrode is the positive terminal.
  • Bromine gain electron, so bromine is reduced to bromide ion.
  • So bromine is the reduced substance.
  • Half equation: Br2 + 2e- --> 2Br-
  • Observation : the brown bromine water turn colourless.

As writing overall ionic equation, a student just need to add both half equation together.

Half equation 2Fe2+ + Br2 --> 2Fe3+ + 2 Br-

Try different questions to see how much you apply the tips given. All the best!

Photos shown my students were working in groups to set up apparatus to study transfer of electrons at at distance.

2009-10-14

Moles



 
Concept of moles is an important concepts in chemistry. Students learn the basic concepts in Chapter 3 Chemical Formulae and Equation during form 4. Later, they relate the moles concepts with molarity of a solution in Chapter 7 Acids and Bases and Chapter 8 Salts.

 
During form 5, students are expected to apply the concept well in various numerical problems in Chapter 1 Rate of Reaction, Chapter 4 Thermochemistry.

Some common wrong concepts that I have come across:
  • students thought that the moles is the same with molarity.
  • they thought that volume refer for both solution and gas.
Plese my dear students, please study the relationship above thoroughly. Whenever come across any question related to this concepts, understand the questions and substitute the value given in the equation correctly.

Form 4 Final Examination SBP Year 2008



Dear form 4 students, please download  this 2008 final exam paper and have a look.

Perhaps it will help you
  • to have a clearer picture about the examination format
  • to identify which areas you are still weak in.
Any doubts about the foming finals, you're always to post  your comments here. 

All the best and enjoy your Deepavali holidays.


The picture is taken from http://annaleeblysse.blogspot.com/

2009-10-13

Trial Chemistry Selangor 2009




Paper 3

Dear visitors, please leave comments about the questions after going through the papers. You're welcomed to leave any doubts/querries about the questions. Thanks.

2009-09-21

A Good Defined Chemistry Term

  I'm always wondering what is in my student's mind when they're asked to define a chemistry terminology. Most of the times they have shown their best effort to explain the terms, but yet missing lots of important key points. Perhaps they didn't really understand the whole idea of the terms.


    A good definition basically has two elements:
  1.  First part explain WHAT is it;
  2.  Second part explain anything about the term. For example: How it happen; What is the properties; When....etc.
Example:
  1. What is the meaning of neuralisation?
   Neutralisaition is a reaction when acid reacts with alkali to  produce salt and water only.

 
   2.  What is empirical formula?

  Empirical formula is a chemical formula that shows the simplest ratio of atoms of each element in a compound.

   3. What is the definition of hydrocarbon?

  Hydrocarbon is a compound that consist of carbon and hydrogen atom only.

   4. What is meant by heat of displacement?

      Heat of displacement is energy change when 1 mol of metal is displaced by a more electropositive metal by its salt solution.


I wish students who sit for SPM compile a list of common chemistry terms and understand them.  The list helps as you can refer it anytime instead of flipping through your thick notes or reference books. If you have any doubts, I'll always ready to help. 

2009-09-20

Trial Chemistry SPM 2009 Johor, Mallaca, Kedah, Pahang, Kelantan, Sabah, Perlis



Trial Johor

Trial Mallaca

Trial Kedah

Trial Pahang
Paper 1; Answer
Paper 2; Answer
Paper 3; Answer

Trial Kelantan

Trial Sabah

Trial Perlis
Paper 1, 2, 3; Answer


Will upload more when I find more questions from other states. Any problems with this exam papers, just click comment and leave your message.

2009-09-16

Trial Chemistry SPM 2009 from Different State

Chemistry Tutor's Blog is worth a visit. You may find
  • Trial Sabah 2009
  • Trial Melaka 2009
  • Trial Kedah 2009
  • Trial Pahang 2009
  • Trial - Times 2009
  • Answering Technique for Paper 3 SPM
  • SPM 2004 - 2008 Analysis
  • WAJA PERAK 2009
~ Practice makes perfect! All the best!

2009-09-11

To determine the end point in the titration of hydrochloric acid and sodium hydroxide solution using acid-base indicator

PEKA 2

Titration is an important method to determine the concentration of a solution.
Through Acid-base titration, concentration of acidic or alkaline solution can be determined.

Format of the Report
(Refer practical book page 103)
  1. Aim
  2. Materials
  3. Apparatus
  4. Diagram
  5. Procedure
  6. Result
  7. Observation
  8. Discussion
  9. Conclusion
Please get ready before come to the lab. You might find video in this blog that show the correct method to carry out acid-base titration. 

Schedule for PEKA is as follows :
4E : 15/9/09(Tuesday)

4D : 18/9/09(Friday)*
*Subjected to changes, might be earlier.

2009-08-28

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.

2009-08-27

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.

2009-08-26

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!

2009-08-25

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?

2009-08-24

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, Vis 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, Vis 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.

2009-08-19

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.

2009-08-15

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.

2009-08-11

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

2009-08-07

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

2009-08-05

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)

2009-07-26

Love Chemistry



Photo taken from one of student's sketch on her exercise. Looks like she enjoys my chemistry class very much.

Learning a subject with enthusiasm will help students to ask, explore and master the subject well.
All the best, Siti Azwa(4E)!

2009-07-19

Perfect Score Chemistry SBP Zon Tengah 2009

From 17 -19 July, my colleague, Ms Foo and I were involved in Perfect Score Chemistry organized by SBP at UKM, Bangi as fasillitators. 3 students each from SAS, SSP, SESERI, ASIS, KISAS, KUSES, SEMASHUR, SMSS, SMAP Kajang, SBPI Sabak Bernam, SBPI Rawang, SBPI Gombak, SEMESTER took part in this activity.



Students worked on different exam-like questions in their own groups and presented their answers in front of other participants and fassilitators. Through their peer group presentation and fasilitators' comments , students learnt. Thanks to all facilitators, Pn Norini, Pn Norlia, Pn Marlina, Pn Norma, Mr Alan, Mr Shukri. Without them, the program wouldn't be carried out smoothly and successfully.


On the first session, I shared with all the participants some tips to score chemistry. In fact I was a bit nervous to talk about the topics especially in front of so many experienced teacher. Surprisingly, it received great response from all the participants. That really means alot to me.

To all the participants, they have shown their enthusiasm throughout the program. They were proactive, creative in giving ideas and fluent in English. All the best to all the participants! Hope all of you will shine.....

2009-07-07

Prefix for Naming of Carbon Compounds

Picture taken is from one my student’s note.


Sounds like part of love letter or some sort of poem. Ha ha…

Actually that’s one of her way to remember the prefix used for naming of carbon compounds.

Mengapameth
Engkaueth
Pergi – prop
Buat – But
Pedih – Pent
Hati – Hex
HambaHept
Oh – Oct
No - Non
Dia - Dec

In my chemistry class, I encourage my students to create stories/interesting sentence for any chemistry keywords/facts. Sometimes they can come up with a very creative idea during their brainstorming session. Their friends might laugh at their ideas, but students tend to remember those dull facts better.
Perhaps, this is one learning strategy you can apply in other subjects too... Through my reading on ways to boost up our memory. Some people even try to visualise each keyword with a picture and link all them in a story.
When I'm free, I'll post more examples of ways to remember chemistry facts......
Thanks Fitri(5C)!

Plastics that Decompose within a Year

Thanks for your efforts, scientist from Universiti Sains Malaysia!!!
reported by The Sun, 25 June 2009. Click the image for more details.

2009-06-23

Fluoride in Toothpaste


Photo taken show ingredients in a type of toothpaste.
Sodium lauryl sulphate is a type of detergent that helps in cleansing our teeth.
Sodium fluoride(NaF) and sodium monofluorophosphate (Na2PO3F) are active ingredients to prevent cavities.

Biodegradable Plastics?

Biodegradable plastic bag from Jusco..

Another one from Tesco...









Both Jusco and Tesco uses biodegradable plastics and encourage their customers to to reuse the plastic bags.

I just found out from news paper, IKEA is no longer provide free plastic bags for its customer. It'll be charged upon customers' request.
I hope with the effort of these giant hypermarkets, the public will reduce the usage of plastic and choose more environmental friendly alternatives. Save our mother earth from plastic...

Detergents and additives

The photo was taken from a type of detergent used to cleaning cloths.

Detergent is a salt formed from the reaction between an alkyl hydrogen sulphate and an alkali.

















Additives are added to make detergent more effective in cleaning.

Examples of additives that can be recognized are:
Optical whitener:
stabiliser:
fragrance:

Funtion of different types of additives in detergent:
  1. biological enzyme : remove protein stains such as blood. E.g. amylase, proteases, lipase.
  2. whitening agent(include bleaches): convert stains to colourless substances, thus make clothes whiter and cleaner. E.g. sodium perborate and sodium hypochlorite
  3. optical whitener: make white clothes look whiter. E.g. fluorescent dyes
  4. fragrances : add freagrance to fabrics.
  5. drying agent: ensure the detergent powder is always dry. e.g. sodium sulphate & sodium silicate
  6. stabiliser : control foaming in detergent. e.g. alkyl monoethanolamide
  7. builder: enhance the cleaning efficiency of detergent by softening the water. e.g. sodium tripolyphosphate
*sodium tripolyphosphate is banned as when it is discharged into lakes, will cause euthrophication.
Normally a box of detergent contains between 15 - 20% of detergent.

Colourful Transition Elements














"Wow!!"

"They're so beautiful!"
Comments by my students when I showed them those colourful chemical in the test tubes.

From the left, it was iron(III) chloride, iron(II) sulphate, copper(II) sulphate, potassium dichromate(VI) and potassium manganate(VII).

Silicon Valley

"A place where silicon is mostly found?

"A place in Malaysia?"
As I discussed about the uses of semi-metal in the microelectronic industries, I asked my students where is Silicon Valley. Above are some examples of responses I get.
Ha ha.. Silicon Valley is at the sounthern part of San Francisco, US. It originally referred to the large number of silicon chip innovators, semi-conductors and computer industries in this area. However, now it refers to the region where most of the leading ICT-based company reside. Companies like Microsoft, HP, Apple, Intel, eBay, Yahoo, Google are headquartered here.
Can we imagine, what would happen to our world without silicon? A world without handphone, ipod, mp3, computer, etc.. out of imagination... My students get stunned when the ideas sank into their deep heart...

Stanford University and its graduates play an important roles towards the development of this area.


Picture taken at Stanford Universtity, San Francisco during my visit during Christmas year 2003.

2009-06-20

All About Moles

Let's start a journey of the mole....
















Any relationship with the mole with the Avogadro Constant, Mass and Volume of Gases?



Five Short Chapters


I
I walk down the street.
There is a deep hole in the sidewalk
I fall in.
I am lost… I am helpless.
It isn’t my fault.
It takes forever to find a way out.

II
I walk down the same street.
There is a deep hole in the sidewalk.
I pretend I don’t see it.
I fall in again.
I can’t believe I am in the same place.
But, it isn’t my fault.
It still takes a long time to get out.

III
I walk down the same street.
There is a deep hole in the sidewalk.
I see it is there.
I still fall in. It’s a habit.
My eyes are open.
I know where I am.
It is my fault. I get out immediately.

IV
I walk down the same street.
There is a deep hole in the sidewalk.
I walk around it.

V
I walk down another street.


AUTOBIOGRAPHY IN FIVE SHORT CHAPTERS
From There’s a Hole in My Sidewalk By Portia Nelson

2009-06-09

Displacement Reaction

I found these two videos on displacement reaction from youtube.com. It's quite interesting! Have a look...

video

(1) Reaction between silver nitrate solution and copper

video

(2) Reaction between copper sulphate solution and iron nail
For the first reaction, reaction between silver nitrate solution and copper
  • copper is more electropositive than silver
  • copper displace silver from its salt solution
  • the silver solid, silver is displaced by copper from its salt solution
  • Chemical equation:
     AgNO3(aq) + Cu(s) --> Ag(s) + Cu(NO)3(aq)
Question: Why does the colourless solution turns blue?
For the second reaction, reaction between copper sulphate solution and iron nail
  • iron is more electropositive than copper
  • iron displace copper from its salt solution
  • the brown solid, copper is displaced by iron from its salt solution
  • Chemical equation: 
      CuSO4(aq) + Fe(s) --> FeSO4(aq) + Cu(s)
Question: Why the intensity of blue copper sulphate solution decrease?
Points to ponder: Why both reaction are examples of redox reaction?

Food Additives in Chili Sauce

Let's try to look at the ingredients in this chili sauce pack?
Besides the main ingredient: Chili, to give a good taste of chili.
of course! Why there are so many other things being added here?
  • permitted food conditioners(modified food starch, Xanthan Gum)
  • permitted preservative(sodium benzoate)
There are known as Food Additives!
Food additives are added into food in small quantity to
  • make food last longer
  • enhance the flavour of food
  • improve food appearance

Can you identify more examples of food additives in some food packages at your homes? Do these food additives bring any harm to human if being consumed in large amount? Looking forward comments on this topic...

2009-06-07

Scoring 1A in SPM Chemistry

Guess scoring 1A in SPM Chemistry is everyone hope. ..

Here is a story from a student, Chong. She said her practice and experience in great details.

http://www.malaysia-students.com/2006/06/scoring-1a-in-spm-chemistry.html

You're welcomed to post your comments after reading the article...

2009-06-05

Heating Curve


The graph shows the heating curve of element Y.
Describe the graph in terms of state of matter, particle arrangements and changes in energy.

From t0 – t1


1 In liquid state


2 Particles are arranged closed to each other but not closely packed together


3 Particles are not arranged in order


4 Energy increases



From t1 – t2


5 In liquid and gas state


6 Some particles are close to each but some are far apart


7 Particles are not arranged in order


8 Energy remains constant//does not increase



From t2 – t3


9 In gas state


10 particles are far apart from each other


11 Particles are not arranged in order


12 Energy increase