Friday, September 30, 2011

Wednesday, September 28, 2011

Earth Scenic From International Space Station

A time-lapse taken from the front of the International Space Station as it orbits our planet at night. This movie begins over the Pacific Ocean and continues over North and South America before entering daylight near Antarctica. Visible cities, countries and landmarks include (in order) Vancouver Island, Victoria, Vancouver, Seattle, Portland, San Francisco, Los Angeles. Phoenix. Multiple cities in Texas, New Mexico and Mexico. Mexico City, the Gulf of Mexico, the Yucatan Peninsula, El Salvador, Lightning in the Pacific Ocean, Guatemala, Panama, Columbia, Ecuador, Peru, Chile, Lake Titicaca, and the Amazon. Also visible is the earths ionosphere (thin yellow line), a satellite (55sec) and the stars of our galaxy.




In the beginning God created the heavens and the earth. 2Now the earth wasa formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters. 3And God said, “Let there be light,” and there was light. 4God saw that the light was good, and he separated the light from the darkness. 5God called the light “day,” and the darkness he called “night.” And there was evening, and there was morning—the first day

........second day........third day ...........fourth day..................fifth day.................On sixth day.......... 

Then God said, “Let us make man in our image, in our likeness, and let them rule over the fish of the sea and the birds of the air, over the livestock, over all the earth,b and over all the creatures that move along the ground.”27So God created man in his own image, in the image of God he created him; male and female he created them. 28God blessed them and said to them, “Be fruitful and increase in number; fill the earth and subdue it. Rule over the fish of the sea and the birds of the air and over every living creature that moves on the ground.”

Physics Form 4: Chapter 4 - Charles's Law of Gas




Charles's law states that for a fixed mass of ideal gas, the volume is directly proportional to its absolute temperature at constant pressure.



Explanation of Charles law by the kinetic theory

·         When the temperature of a gas in an enclosed cylinder is raised, the gas molecules receive heat energy and their average kinetic energy increases.
·         This means that molecular velocity will increase and the frequency of collision between the molecules and the wall of the cylinder also increases. Thus, the gas pressure increases.
·         Increase in pressure will cause the piston to be pushed up and this indicates that the volume of the gas has increased.
 

Click on the diagram below to play!

Chemistry Form 4: Chapter 7 - Neutralization Reaction


As you can see from the equations, acids release H+ into solution and bases release OH-. If we were to mix an acid and base together, the H+ ion would combine with the OH- ion to make the molecule H2O, or plain water:


H+(aq) +   OH-(aq)  arrow H2O
Neutralization is a reaction between acid and base to produce salt and water only as shown below:

Acid
Base
Water
Salt
HCl  +  NaOH  arrow H2O  +  NaCl
HBr  +  KOH  arrow H2O  +  KBr

Uses of neutralization
  1. Soil treatment - if the soil is too acidic, it is treated with a base in order to neutralise it. Common treatments use quicklime (calcium oxide) or chalk (calcium carbonate). 
  2. Indigestion -  too much hydrochloric acid in our stomach leads to indigestion. Therefore, to cure this ailment we need to neutralise the acid with a base such as, sodium hydrogen carbonate (baking soda), or milk of magnesia. 
  3. Bee sting contains acid -  In order to relieve the painful symptoms of the sting we need to neutralise the acid. By rubbing on calamine lotion (zinc carbonate) or baking soda the acid can be neutralised.
  4. Wasp sting contains alkaline -  Hence acid is needed to neutralise and remove the painful sting. Vinegar (ethanoic acid) is used.

    Tuesday, September 27, 2011

    Physics Form 5: Chapter 5 - Einstein Equation, Mass-Energy Equivalence



    In 1905, Albert Einstein published his theory of Special Relativity. In this paper, Einstein took his readers through the thought process which led him to the most famous equation, E = mc².


    Introduction to mass and energy
    Mass is a measurement of how much quantity of matter inside of an object. Mass is also a measure of inertia - the more mass an object has, the harder it is to move and once it is moving, the harder it is to stop it. On the hand, energy is the ability to do work. Mass and energy can be neither created nor destroyed. While they can be converted into different forms (mass can turn from solid to liquid to gas, and can be cut up or turned to dust, while kinetic energy can be transferred to potential energy or sound energy or heat energy), there will always remain the same amount in our universe.

    Einstein's way to explain mass and energy
    Einstein began, it is said, by looking at the equation for finding an object’s kinetic energy:


    Einstein was able to take this equation, combine it with other known equations, do a little bit of math, and come up with the following:


     
    The equation most people are familiar with, E = mc², can be obtained by assuming that the “object” in question has a speed of zero. If an object is perfectly still, the entire right half of the equation cancels out, and we are only left with the familiar equation.

    This equation shows that Mass and Energy are not just similar – they are the same thing, but in different forms, with the ability to be converted into one another. Mass can be turned into energy, and energy can be turned into mass. Further, this equation shows us that a tiny bit of mass can be turned into a lot of energy (the equivalent of the amount of mass times the speed of light squared!), while a lot of energy can only be turned into a little bit of mass.

    The equation truly was a revolutionary one, though no one knew just how much so until it was realized that it would be possible, using radioactive elements, the atomic bomb, and later atomic energy.

    It is Einstein’s equation which helped scientists predict just what would happen when that first nuclear explosion was triggered, and it is what tells particle physicists what will happen when they smash two beams of particles together in an accelerator.

    Thursday, September 22, 2011

    Physics Form 4: Chapter 4 - Absolute Temperature

    • Temperature is a measure of the average kinetic energy of a system particles. When temperature rises, the average kinetic energy of particles also increases.
    • Temperature is the degree of hotness, a measure of heat intensity.

    Absolute temperature is based on the Kelvin scale. Units on the Kelvin scale are called Kelvins (K) and no degree symbol is used.






    The concept of an absolute zero of temperature evolved in connection with experiments with gases. When a fixed mass of gas is cooled at a constant pressure (volume), its volume (pressure) decreases with its temperature. A plot of the experimental values of volume (pressure) versus temperature can be extrapolated to cross the temperature axis when the volume (pressure) would be zero. The temperature is the absolute zero of temperature. It is -273.15 °C, or more approximately -273 °C.


    What happens to the matter at absolute zero temperature?
    At absolute zero temperature, it's the point at which particles have a minimum energy. Near absolute zero, the matter stops acting the way it should and starts exhibiting some strange properties. Some types of matter become superconducting, carrying electric current with absolutely no resistance, and some of them, like helium, become superfluid at this temperature, exhibiting absolutely no friction, becoming a Bose-Einstein Condensate (BEC). This means that a droplet of superfluid helium can rotate inside a container forever, as if it were in a vacuum.


    So far, this temperature has never been achieved, and in theory it could never be achieved. In 1994, the NIST achieved a record cold temperature of 700 nK (billionths of a kelvin). In 2003, researchers at MIT eclipsed this with a new record of 450 pK (0.45 nK).

    Tuesday, September 20, 2011

    This Is Called Life

    人生何其短華髮換白頭

    May all of you have abundant life 

    Monday, September 19, 2011

    Physics Form 5: Chapter 5 - Ionizing Power and Penetrating Power


    Type of Radiation
    Alpha particle
    Beta particle
    Gamma ray
    Symbol
    α
    β
    γ
    Mass (atomic mass units)
    4
    1/2000
    0
    Charge
    +2
    -1
    0
    Speed
    slow
    fast
    very fast (speed of light)
    Ionising ability
    high
    medium
    weak
    Penetrating power
    low
    medium
    high
    Stopped by:
    paper
    aluminium
    lead


    Alpha particle:
    • It carries +2 charge and exerts greater forces on the neighbouring air molecules.
    • It moves at a relatively low speed. The chance of ionising the neighbouring molecule is higher.
    • It has a strong ionising power and it loses kinetic energy readily to ionise the air molecules along its path. So it has absorbed in the air quickly.
    Beta particle:
    • It carries -1 charge and exerts smaller forces on the air molecules.
    • It travels faster and the chances of ionising the neighbouring molecules are lower.
    • It has much weaker ionising power. So it loses kinetic energy at lower rate. Thus, it has a stronger penetrating power than alpha.
    Gamma particle:
    • It is electrically neutral and travels very fast at the speed of light.
    • Ionising effects only occur when they collide directly with the air molecules. Since the chances for such a collision are very slim, gamma rays seldom produce ion pairs.
    • It is a high frequency electromagnetic wave and it possess the highest energy.
    • It has extremely weak ionising power. So it loses kinetic energy at the lowest rate.

    Chemistry Form 4: Chapter 7 - pH Scale

    • The pH scale is used to measure degree of the acidity or alkalinity of an aqueous solution based on the concentration of hydrogen ions.
    • pH is defined as the concentration of hydrogen ions in solution.

    Click on the diagram below to play!

    1. The higher the concentration of H+ , the lower the pH value.
    2. The higher the pH value, the higher the concentration of hydroxide ions.
    3. At pH =7, the concentration of H+ ions is equal to the concentration of OH- . The solution is termed as being neutral for example pure water.
    4. The stronger an acid, the lower of its pH value.
    5. The stronger an alkali, the higher of its pH value.

    Click on the diagram below to play!

    Wednesday, September 14, 2011

    Physics Form 4: Chapter 4 - Boyle's Law of Gas

    Boyle's law states that the pressure of a fixed mass of gas is inversely proportional to the volume of gas provided the temperature of the gas is constant.

    The law was first proposed in 1662 by Robert Boyle

    Because pV = constant that means that p1V1 = constant and so does p2V2. We can therefore write:
     
    where
    V1 = equals the original volume,
    V= equals the new volume,
    p1  = the original pressure, and
    p2  = the new pressure.





    Explanation of Boyle's law by the kinetic theory:

     

    • At constant temperature, the average kinetic energy of the gas molecules is constant.
    • When the gas is compressed, the volume is decreased. Therefore, the number of molecules per unit volume will increase.
    • The rate of collision of the gas molecules with the wall of container will increase.
    • Thus, the pressure of gas increases.

    Tuesday, September 13, 2011

    Physics Form 5: Chapter 5 - Application of Radioactive (Carbon-14 Dating)

    C-14 is another radioactive isotope that decays to C-12. This isotope is found in all living organisms. Once an organism dies, the C-14 begins to decay. The half-life of C-14, however, is only 5,730 years. Because of its short half-life, the number of C-14 isotopes in a sample is negligible after about 50,000 years, making it impossible to use for dating older samples. C-14 is used often in dating artifacts from humans.


    (Real mummy from Ramesses II)
    How old is he ..............?
     

    For determining age of fossils older than 60,000 years one uses a potassium-argon dating technique. Potassium dating has a half life of 1.3 billion years, thus allowing the age of rocks several billions years old to be determined. A more accurate "argon-argon" dating technique (determining the ratio between argon-39 and argon-40) has also been developed.

    Monday, September 12, 2011

    6 Principles of Life on MONEY

     1.   No point using limited life to chase after unlimited money.

     2.   No point earning so much money you cannot live to spend it.

     3.   Money is not yours until you spend it.

     4.   When you are young, you use your health to chase your wealth; when you are  old, you use your wealth to buy back your health. The difference is that it is too late.

     5.   How happy a man is, is not how much he has but how little he needs.

     6.   No point working so hard to provide for the people you have no time to spend with.



    Sunday, September 11, 2011

    Chemistry Form 4: Chapter 7 - Strength of Alkali

    The strength of alkali depends on the degree of dissociation of the alkali in water to produce hydroxide ions. The pH of an alkali solution depends on the concentration of hydroxide ions.



    Strong Alkali
    Weak Alkali
    ·     Strong alkali have a higher degree of dissociation.
    ·     A strong alkali is an alkali which dissociates completely in water to produce a high concentration of hydroxide ions.
    ·     Thus, pH value for strong alkali is higher than weak alkali.

    ·     Weak alkali have a lower degree of dissociation.
    ·     A weak alkali is an alkali which ionises partially in water to produce a low concentration of hydroxide ions. Only a part of the molecules ionises and the remaining still in covalent molecules.
    ·     Thus, pH value for weak alkali is lower than strong alkali.


    Click on the diagram below to play!

    Saturday, September 10, 2011

    Chemistry Form 4: Chapter 7 - How to Differentiate Between Strong Acid and Weak Acid

    A) Reaction between acids and reactive metals

    • Strong acids can react with reactive metal faster and more vigorously. More hydrogen gas produced at a faster rate.
    • Weak acids can react with reactive metal slower and less vigorously. Less hydrogen gas produced at a slower rate.
    B) Electrical conductivity

     

    Conductivity Behavior of Acids 
     Compounds
    Appearance of light bulb

     Classification
    Weak or Strong

     Inference of Ions or Molecules
     water, H2O  no light  weak  molecules
     hydrochloric acid, HCl  bright  strong  ions
      acetic acid, HC2H3O2  dim  weak mostly molecules, less ions
    • Strong acids able to conduct electricity better as shown in hydrochloric acid because it contains a large number of freely moving ions as strong acids dissociate completely in water.
    • Weak acids conduct electricity weakly as shown in acetic acid because it contains a few number of moving ions as weak acids dissociate partially in water. Most of weak acids still remain in covalent molecule.

    Physics Form 4: Chapter 4 - Latent Heat

    Latent heat is the quantity of heat absorbed or released by a substance to change its physical state without any change in temperature.
     
    • Specific latent heat of fusion is the quantity of heat needed to change 1kg of a solid to liquid at its melting point without change in temperature.
    • The temperature does not change even though heat is being absorbed by the solid particles. This is because the heat absorbed does not increase the kinetic energy of particles but is used to overcome the force of attraction between the particles.

    • Specific latent heat of vaporization is the quantity of heat needed to change 1kg of a liquid to gas at its boiling point without change in temperature.
    • The temperature does not change even though heat is being absorbed by the liquid particles. This is because the heat absorbed does not increase the kinetic energy of particles but is used to overcome the force of attraction between the particles.


     
    Specific latent heat of vaporization is greater than its specific latent heat of fusion because:
    • More energy is required to break the bonds between liquid molecules in order to change into gas phase.
    • Extra energy is required to overcome atmospheric pressure.
    • Energy is used to overcome the surface tension of a liquid when its molecules change into the gas phase.
       
    Further information about latent heat

    Tuesday, September 6, 2011

    Physics Form 5: Chapter 5 - Half Life of Radioisotopes

    • Half life is the time taken for radioisotope to decay to half of its original quantity. 
    • Different radioisotope have different value of half life.


    The half life formula is an exponential equation:

    where Nt is the remaining substance after time t, N0  is the initial amount of the substance, t1/2  is the half life of the substance, and t is the elapsed time.


    Click on the diagram below to play!
     


    Radioisotope will continue to decay to form new atom until it becomes stable