Thursday, June 30, 2011

Physics Form 4: Chapter 3 - Gas Pressure

Gas pressure in a closed container is caused by the frequency of collision between the gas molecules and the walls of the container. All collisions are elastic.


A molecule with a mass, m moving with a velocity  v, has a momentum = mv

After colliding with the wall elastically, the  momentum with it bounces back is   –mv.

Change in momentum = mv – (-mv) = 2 mv. Thus, produce an impulsive force. The force acting on an area of the wall produces pressure in the container.

 Gas pressure can be increased by:
  • increasing the temperature of the gas
  • reducing the volume of the gas.
  • increasing the number of gas particles.
 Gas pressure can be measured by using manometer as shown below:



Click on the diagram below to play!

Sunday, June 26, 2011

Chemistry Form 4: Chapter 6 - Types of Electrodes Affect Product of Electrolysis

  • Carbon dan platinum electrodes are inert because both of these materials do not react with the electrolytes or the product of electrolysis.
  • Other electrodes except carbon and platinum can react with the electrolytes.
Click on the diagram below to play!

Saturday, June 25, 2011

Federal scholarships for undergrads, not SPM top scorers from 2012

PETALING JAYA, June 23 — The Najib administration has decided to only give Public Service Department (PSD) scholarships to university entrants instead of SPM top scorers from 2012 to avoid the distress they have caused in past years. Prime Minister Datuk Seri Najib Razak however said those who do well in the Form Five SPM examination will receive small bursaries instead to pursue their foundation studies.

“Scholarships will be reserved if you are able to get very good results (at foundation) and (a) place at top universities,” said Najib (picture) in an interview with the Chinese-language One FM radio station today.

“Giving out scholarships at SPM level is not a good idea... Just because you do well at O-levels doesn’t mean you’ll do well at A-levels,” he added. Putrajaya gives out 1,500 scholarships annually and has asked government-linked companies to also offer money for top scorers.

MCA president Datuk Seri Dr Chua Soi Lek had said last week public examinations are too easy, leading to a high number of top scorers seeking scholarships.

Asked which universities were deemed “top” institutions, Najib said they would be identified in due course.
The PM also stressed that not all top students will be given overseas scholarships. “Our universities here need top students as well. Here, we complain our universities are not ranked highly in terms of the world ranking,” he said. “At the same time we insist on sending our top students abroad. It is a contradiction in terms of what we want to achieve,” he added.

The ranking of public institutions in Malaysia has dived through the years to the point of dropping out of the top 200 universities in the QS World University Rankings last year. Six out of seven Malaysian universities, however, improved their ranking on the QS Asian University Rankings this year, with Universiti Malaya climbing three spots to 39th, although no Malaysian university entered the top 10 ranks.

Despite Putrajaya handing out 500 special local scholarships recently on top of the 12,000 PSD grants it gives out annually, many top scorers were still disappointed they did not receive government funding to study overseas.The main bone of contention in the annual allocation of PSD scholarships centres around the 1,500 overseas grants, of which only 20 per cent are decided based on merit. Nine hundred are given out based on racial quotas, with Sabah and Sarawak natives getting 75 grants each and the remaining 10 per cent to special needs students.

Chemistry Form 4: Chapter 6 - Electrolysis of Concentrated of Sodium Chloride Solution


Electrolysis of dilute sodium chloride solution
Electrolysis of concentrated sodium chloride solution
At
anode :








Anions :  OH-   and   Cl-

OH- ions are selectively discharge according to the position of ions in the Electrochemical Series, ES. 

Gas bubbles are formed which lighted up a glowing wooden splinter. This gas is oxygen.

4OH- ---> 2 H2O  +  O2   +  4e


At
anode :








Anions :  OH-   and   Cl-

Cl- ions are discharged instead of OH- because of their higher concentration in the electrolyte.

A greenish-yellow gas with a pungent and choking smell is released. The gas turns the blue litmus paper red and then white.

2Cl-  --->  Cl2    +     2e

At cathode:
Cations :  H+   dan   Na+

H+ ions are selectively discharge according to the position of ions in the ES.

Gas bubbles are formed. When a lighted wooden splinter is placed near the mouth of   the test tube, a ‘pop’ sound is produced.  Hydrogen gas is produced

        2H+   +   2e ---> H2
       
At cathode:
Cations :  H+   dan   K+

H+ ions are selectively discharge according to the position of ions in the ES.

Gas bubbles are formed. When a lighted wooden splinter is placed near the mouth of the test tube, a ‘pop’ sound is produced.  Hydrogen gas is produced

    2H+   +   2e ---> H2


Thursday, June 23, 2011

Killing the teachers, zombifying our children


Opinion by Erna Mahyuni from Malaysian Insider


JUNE 22 — There is only one thing our schools are good for these days: Creating the living dead. I don’t just mean our “national” schools but all our schools. An education these days is not about preparing the next generation for the future, but the business of scoring on standardised tests. We covet soulless parrots, with the ability to regurgitate whatever information was crammed down their throats along with the insipid “values” our education system attempts to inculcate. Moral Education, for instance, is a stupid subject that exists only to allow students to get one more A.

When I was part of the Barisan Nasional Youth Lab (yes, taxpayers, I apologise for wasting your money), I remember one member spouting that what our kids needed were guides on “how to study.” Essentially, his idea of education was teaching children the best way to study to get the highest marks. The amazing thing was how the other lab members shot him down, some with biting, cutting remarks. The poor bloke never came back to another lab session.

But who can blame him? Achievement is based on testing, scoring, exams. I wait for the day that students’ worth is not measured by how many A’s they can score but for their unique talents. That day will not come too soon for our overburdened teachers trapped in a system that makes it challenging to do what they’re supposed to do — teach. Teachers I know have a snarky alternative meaning for our national curriculum, KBSM. They say it stands for Kerja Berat Sampai Mati (work hard, until death). Look at the workloads teachers have to cope with and you would probably agree with them.

Teaching, like journalism, is not a profession for those who want to get rich. It is hard work, made complicated by bureaucracy and whoever is heading the Education Ministry. It is no secret that the education portfolio is a coveted one, for it gives its bearer the power to drive high-visibility initiatives that in the end, seem to benefit no one. How can you expect teachers to concentrate on the business of educating their charges when they have countless reports to hand in on various useless minutiae? Let the administrators administrate, and the teachers get on with the business of moulding young minds.

A friend of mine recently joined the Teach for Malaysia initiative; her eyes go all starry-eyed when she talks about how fresh, unspoiled graduates will go in and change the lives of deserving underprivileged children. She got quite upset by the reception and cynicism she met from teachers who told her that it was a waste of time trying to teach the children of hawkers or of particular races. That these children would not, no, could not amount to anything. She says these jaded teachers give up too soon. That if they know their charges aren’t being fed enough, they should be doing more for the children, meeting up with the parents personally and actively make a difference. 

The Teach for Malaysia teachers will do all that and more, hunting for sponsors for underfed children if they must. I hate to sound like a spoilsport but she highlights one problem with our society — we ask far too much of our teachers and give little in return. For too little pay for too much work, teachers are supposed to be godparents as well? I’m not saying there aren’t bad teachers. Plenty of teachers neglect their charges at school, prioritising those monied enough to pay them for after school tuition. There are the lazy ones who became teachers because they wanted an “easy” job or could not secure another profession. These individuals should be culled from the teaching body and told they are not welcome.

As the saying goes, it takes a whole village to raise a child. Therefore it takes a nation to raise all our children. We shouldn’t be vilifying our teachers and pointing the blame in their direction. The system has failed them. We who have done nothing, said nothing, sent our children to private schools... we have failed the teachers and by doing so, failed our children. Too many of us suffer from an insidious selfishness. Why care about other children besides our own getting an education? But it is our duty as citizens to care.

Politicians, for all their big speeches, cannot be depended on to push educational reform with a political agenda. Parents on the other hand, will do it because they are parents. They know better than most that bringing up a child shouldn’t be graded with a KPI.

It is time for parents to step up to the plate at schools, support those tasked as temporary guardians. One school might not change the system but all the schools together, demanding educational reform? We just might get somewhere.


* The views expressed here are the personal opinion of the columnist.

Wednesday, June 22, 2011

Physics Form 5: Chapter 3 - Transmission of Electricity



Electricity is transmitted mainly through overhead lines or underground cables. Due to the resistance of the transmission wires, there is always some loss of power through the heating effect of current. The electricity transmission systems must be designed in ways which reduce this loss as much as possible.

High voltage transmission
Electricity generated in power stations is raised to a very high voltage for transmission. This is to reduce the current flow to the transmission cables.
Ploss = I 2R

The power loss is proportional to the square of the current, thus a small current greatly reduces heat loss. As seen from the equation above, a small current can be achieved by using a high voltage. For example, if we double (×2) the transmission voltage, the current would be halved (×1/2), and the power loss would be reduced to a quarter, (1/2)2 = 1/4, i.e. 25% of the original value.

Low Resistance Transmission Wire
We see from the equation above that the power loss in the transmission wire Ploss is directly proportional to the resistance R of the wire. The lower the resistance, the lower will be the power loss. Copper and aluminium are the most commonly used metals in transmission wires. They are very good conductors, cheap, resistant to corrosion, and strong. The resistance of the transmission wire is lowered by making the wire thicker. Thicker wires have larger cross-sectional areas and therefore lower resistance.

Electrical Transmission by Overhead Wire
Overhead lines are held high above the ground by metal towers called pylons. If you look at a pylon carefully, you will see that the overhead lines are held by a stack of discs hanging from the pylon. This stack of discs is a series of suspended insulators which prevents the line from being electrically connected to the pylon. This prevents the electrical leakage from transmission wire to the ground.

Insulating disc

Monday, June 20, 2011

Physics Form 4: Chapter 3 - Atmospheric Pressure

Atmospheric pressure is the force per unit area exerted against a surface by the weight of air particles in Earth's atmosphere.

Click on the diagram below to play!



Units of atmospheric pressure:
1 atm = 105 Pa
105 Pa = 105 N m-2  

Barometer mercury gives atmospheric pressure to 76 cm Hg 

Vertical column of water gives atmospheric pressure to 10.3 m.


 
  • Atmospheric pressure depends on the height of a place above sea level and decreases with altitude. At higher altitude, the density and temperature of the air are lower, so the number of collisions between molecules are less and the pressure is lower.
  • Atmospheric pressure can be measured by using barometer mercury, barometer Aneroid and barometer Fortin 
Barometer Aneroid

Barometer Fortin

Friday, June 17, 2011

Chemistry Form 5: Chapter 3 - Redox Reaction

  • Redox reactions are chemical reactions involving oxidation and reduction occurring simultaneously.
  • Oxidising agent is the substance that causes oxidation.
  • Reducing agent is the substance that causes reduction.

Oxidation involves loss of electrons and increase in oxidation number.
Reduction involves gain of electrons and decrease in oxidation number.

Example:


The magnesium's oxidation state has increased from 0 to +2 , it has been oxidised. Magnesium acts as reducing agent. The hydrogen's oxidation state has decreased from +1 to 0 ,  it has been reduced. The hydrogen ion acts as a oxidising agent.

Click on the diagram below to play!




There is no change in oxidation number. Therefore, this is not a redox reaction.

Wednesday, June 15, 2011

Physics Form 4: Chapter 3 - Liquid Pressure

Liquid pressure is due to the weight of liquid acting on the surface of any objects in the liquid.


P = Pressure
h = depth
ρ = density of liquid
g = Gravitational Field Strength
Liquid pressure increases with depth. The deeper the object in the liquid, the higher the pressure exert on the object.


Pressure acts in all direction perpendicularly to the surface area of the object.


 Pressure in liquid does not depends on
- the size of the container.
- the area of its surface 
- the shape of the container







Pressure in liquid depends only on its vertical distance from the surface of the liquid.

Pressure at A = Pressure at B

Tuesday, June 14, 2011

JPA offers 4,000 scholarships to SPM holders

Written by Bernama   
Monday, 13 June 2011

KUALA LUMPUR: The Public Service Department (PSD) has offered 1,500 scholarships under the overseas degree programme (PILN) and 2,500 scholarships under the local degree programme (PIDN) for Sijil Pelajaran Malaysia (SPM) 2010 holders. Minister in the Prime Minister's Department Datuk Seri Mohamed Nazri Aziz said on Monday, June 13 882 Bumiputera students and 618 non-Bumiputera students received the scholarships under the PILN.

For the local degree programme this year, 1,301 Bumiputera students and 1,199 non-Bumiputera students received scholarships, he said during the question-and-answer session in the Dewan Rakyat, here. Nazri said the 10 per cent allocation for Sabah and Sarawak Bumiputera students remained, with 75 from Sabah offered scholarships for studies overseas under this category. Besides that, he said, Sabah's students were offered study sponsorship overseas under the Academic Excellence category, bringing the total number of Sabah students sponsored under the PILN in 2011 to 77.

"The government has allocated RM1.44 billion for PSD sponsorship this year of SPM 2010 holders, with RM0.36 billion of the sum for studies at local higher learning institutions and RM1.08 billion for studies abroad." Nazri said among the reasons for many excellent students not being offered scholarships to study overseas was the increased number of top scorers and imited government funds.

"There were also many bright students choosing popular fields of study like medicine and engineering compared to arts and science, causing them not being offered scholarships to study overseas as the offer also depends on the public sector and country's manpower needs. "The PSD will review and improve the existing policy in the future to avoid the scholarship offers from becoming an issue each year."

Saturday, June 11, 2011

Chemistry Form 4: Chapter 6 - Electrolysis of Lead (II) Bromide

  • Electrolysis is a chemical process where a substance in its molten state or in an aqueous solution decomposed by electric current.
  • This involves conversion of energy from electrical energy to chemical energy.
  • Electrodes are the strips of metals inserted into electrolyte for conduction of electricity. he metal electrode connected to the positive terminal of the battery is called the anode (+). The metal electrode connected to the negative terminal of the battery is called the cathode (-).
  • Electrolytic cell is the complete set-up for electrolysis. This consists of the vessel containing the electrolyte, anode, cathode, battery and  wires. 




At the CathodeAt the Anode
Observation
  • When electricity is flowing, a silvery deposit of lead metal forms on the cathode. In fact, as it is molten, it is more likely to drip off in a molten blob.
Observation
  • When electricity is flowing, brown fumes of bromine gas are seen at the anode.
Half equation
Pb2+ + 2e ---> Pb
Half equation
2Br- ---> Br2 + e
Explanation
  • The lead(II) ions, as they are positive, move to the negative cathode, where each ion gains two electrons to form a lead atom.
  • Any reaction at a cathode involved  a gain in electrons. This is called reduction or more exactly, cathodic reduction .
Explanation
  • The bromide ions, as they are negative, move to the positive anode, where each loses an electron to form a bromine atom.
  • Then two of these newly formed atoms combine to form bromine gas.
  • Any reaction at an anode involves a loss of electrons.

Tuesday, June 7, 2011

Physics Form 5: Chapter 3 - Transformer

Transformer is an electrical device which increases and decreases an alternating voltage. Transformer only works with alternating current


How transformer works:
  • A transformer works on the principle of electromagnetic induction.
  • When the a.c voltage, Vp is applied to  the primary coil, an alternating current flows through the coil. The soft iron core is magnetized in one way and then the other.
  • This causes a changing magnetic flux to pass through the secondary coil producing an a.c voltage Vs.  
 

Types of transformer:
  1. Step up transformer:  The number of turns in the secondary coil is more than the number of turns in the primary coil. Output voltage is higher than the input voltage.
  2. Step down transformer: The number of turns in the primary coil is more than the number of turns in the secondary coil.
Click on the diagram below to play!


Monday, June 6, 2011

Chemistry Form 5: Chapter 3 - Rules of Oxidation Number

There are several rules for assigning the oxidation number to an element. Learning these rules will simplify the task of determining the oxidation state of an element, and thus, whether it has undergone oxidation or reduction.
  1. The oxidation number of an atom in the elemental state is zero.
    Example: Cl2 and Al both are 0 
  2. The oxidation number of a monatomic ion is equal to its charge.
    Example: In the compound NaCl, the sodium has an oxidation number of 1+ and the chlorine is 1-.
  3. The algebraic sum of the oxidation numbers in the formula of a compound is zero.
    Example: the oxidation numbers in the NaCl above add up to 0
  4. The oxidation number of hydrogen in a compound is 1+, except when hydrogen forms compounds called hydrides with active metals, and then it is 1-.
    Examples: H is 1+ in H2O, but 1- in NaH (sodium hydride).
  5. The oxidation number of oxygen in a compound is 2-, except in peroxides when it is 1-, and when combined with fluorine. Then it is 2+.
    Example: In H2O the oxygen is 2-, in H2O2 it is 1-.
  6. The algebraic sum of the oxidation numbers in the formula for a polyatomic ion is equal to the charge on that ion.
    Example: in the sulfate ion, SO42-, the oxidation numbers of the sulfur and the oxygens add up to 2-. The oxygens are 2- each, and the sulfur is 6+.

Saturday, June 4, 2011

Physics Form 4: Chapter 2 - Force Acting on a Skydiver

When an object falls, it accelerates. As its speed increases, the air resistance increases.
Eventually, the force from the air resistance will equal the force from the weight of the object.

At that point, the speed will remain constant: the object has reached its "terminal velocity" and can't fall any faster.


Click on the diagram below to play!

Physics Form 4: Chapter 3 - Pressure

  • Pressure is defined force per unit area applied in a direction perpendicular to the surface of an object
  • The unit of pressure is Pascal.
  • The larger the area of surface, the lower the pressure exerted on an object.
  • The greater the force, the higher the pressure exerted on an object.
 Application of pressure:
When the area is small, a moderate force can create a very large pressure. This is why a sharp knife is good at cutting things: when you push the very small area of the sharp blade against something, it creates a really large pressure.



Supermodel can damage floors by walking on then in high-heeled shoes. This is because the area of the heel is small, so you can easily create enough pressure to cause a dent in the floor.



Camels have large feet to increase surface area of contact with sand. Pressure produced is small. This is why a heavy camel will not sink into sand while walking on dessert.

Wednesday, June 1, 2011

Chemistry Form 4: Chapter 6 - Electrolyte

  • Electrolyte is a chemical substance which conducts electricity in the molten or aqueous state.
  • Electrolytes are able to conduct electricity because there are freely move ions in the molten or aqueous state.
  • Examples of electrolyte are salt solution, dilute acids and dilute alkalis 
Click on the diagram below to play!