Chemistry

Curriculum

S3 (Compulsory part)

  • Topic I Planet Earth

S4 (Compulsory part)

  • Topic II Microscopic World I
  • Topic III Metals
  • Topic IV Acids and Bases
  • Topic V Fossil Fuels and Carbon Compounds
  • Topic VI Microscopic World II

S5 (Compulsory part)

  • Topic VII Redox Reactions, Chemical Cells and Electrolysis
  • Topic VIII Chemical Reactions and Energy
  • Topic IX Rate of Reaction
  • Topic X Chemical Equilibrium
  • Topic XI Chemistry of Carbon Compounds
  • Topic XII Patterns in the Chemical World

S6 (Elective part)

  • Topic XIII Industrial Chemistry
  • Topic XV Analytical Chemistry

Weighting of Papers

S3

Items Weighting
Lesson Performance and Co-operative Learning 5%
Assignment 15%
Test 20%
Exam 60%

S4

Items Weighting
Lesson Performance and Co-operative Learning 5%
Assignment 15%
Test 20%
Exam 60%

S5

Items Weighting
Lesson Performance and Co-operative Learning 5%
Assignment 15%
Test 20%
Exam 60%

S6

Items Weighting
SBA 20%
Exam 80%

Life Chemistry

Blowing Bubbles

Blowing bubbles must be something that adults and children love to play, The colorful bubbles make people dream like a fairy tale, But beautiful things are always very short, The bubble disappears in a few seconds! How good would it be to have a bubble that would never break ...

Do you know why bubbles form a ball in the air? How did the colorful neon above come from? Usually the liquid we use to blow bubbles is soapy water, and the soap molecule is a "surfactant". That is, the molecule has two ends, one end is a "hydrophilic end" attractive to water molecules, and the other end is a "hydrophobic end" that does not dissolve in water. Because the membrane of soap bubbles is composed of two layers of soap molecules and contains a small amount of aqueous solution, they are arranged in layers like a sandwich biscuit. Also because the bubble is maintained by the flow of water, the bubble will break as long as it touches the dry thing. If we wet our hands, the water on our hands will become a part of the bubbles when touching the bubbles, which is not easy to break!

As for why there is a rainbow on the bubble? It turns out that the thickness of the bubble film is different from the wavelength of visible light, so the light hitting the film will cause interference after reflection and refraction. This is the same principle as the rainbow appears! However, the water in the bubble film will gradually be lost due to gravity or evaporation, resulting in a thinner film, so the rainbow gloss will become less and less obvious. In other words, we can also judge the thickness of the bubble film by the color on the bubble film! When the bubble becomes dull and dull, it means that it is almost broken.

From the principle point of view, we can know that the thickness of the bubble film must be maintained, and the bubble will not break easily! Therefore, we can use a sawtooth blower when choosing a bubble blowing tool to increase the contact area with moisture, so that the bubble film can be thicker.

In addition, we can also use external force to make the bubble not easy to break, that is to increase the speed of movement during the bubble blowing process. There are experiments abroad to blow bubbles on the jet machine, it is really not easy to break it!

Alcohol Chemistry

Three cups of beer will make you feel happy and relaxed, but if you drink too much, you will get uncomfortable when you get up next day. Hangovers such as headache and nausea, vomiting, thirst, dizziness, fatigue, etc., but what is causing the hangover in the body?

First of all, let us understand the metabolic process of alcohol in our body! The main component of wine is ethanol (C2H5OH). Alcohol is a general term for an organic compound that has a hydroxyl group (-OH) composed of a hydrogen atom and an oxygen atom. When alcohol is metabolized by "ethanol dehydrogenase (ADH)" to toxic acetaldehyde (C2H4O), it is then metabolized by "acetaldehyde dehydrogenase (ALDH2)" to non-toxic acetic acid (CH3COOH).

"Acetaldehyde" can cause headaches, nausea, and nausea, so when we consume too much alcohol and the body lacks ALDH2, the removal of "acetaldehyde" is slow, causing the concentration of acetaldehyde in the blood to increase. When the amount of ADH is insufficient, acetaldehyde cannot be decomposed and remain in the body, causing a hangover and causing the following symptoms:

  1. Dehydration: Alcohol is regarded as a diuretic, which will cause the kidneys to produce more urine, so there will be dehydration and electrolyte imbalance, and thirst, dry mouth, headache and nausea.

  2. Gastrointestinal discomfort: Alcohol may irritate the stomach and cause inflammation. It may also cause abdominal pain or nausea due to increased stomach acid.

  3. Lower blood sugar: drinking alcohol will limit the production of sugar (glucose) in the body. If blood sugar drops, you will feel weak or tired.

However, the degree of hangover actually varies from person to person, and the intensity ranges from light to heavy. The decomposition power of acetaldehyde dehydrogenase in different races is also different. In 1983, Assistant Professor Harada Katsuda of the University of Tsukuba, Japan, did a survey and found that Europeans have stronger acetaldehyde dehydrogenase activity, while Asians have more acetaldehyde dehydrogenase activity than Europeans The power is relatively weak.

In fact, there are many reasons for hangovers. For example, the effect of the amount of alcohol added may be one of the causes of hangovers. In order to enhance the flavor of the wine, additives are added to the wine. If two alcohols with the same alcohol concentration are compared, if the content of the additive is smaller, the hangover symptoms caused are also mild.

The next time you drink alcohol, remember to measure your physical condition first. Do n’t drink too much, hurt your body, and hangover all day next day, resulting in poor physical condition and unable to do things well. And if the amount of wine is good, if the amount is appropriate, be careful of the "liver"!

Legend of Ghost Fire-Peek into the secrets in "Ghost Fire"!

In many animations in Japan, when the protagonist comes near the cemetery, There were yellow flames floating around in the air, The protagonist immediately shouted: Ghostfire! ! ! What happened? How did these flames appear? What is their true identity?

Ghost fire, "phosphorus fire", is a natural phenomenon. The reason for the formation of phosphorus fire is actually very simple, because the animal's bones contain a large amount of calcium phosphate (Ca3(PO4)2), after a long time of change, these calcium phosphate will gradually become phosphine (PH3).

Phosphine is a gas substance at normal temperature and pressure, and its spontaneous ignition temperature is only 38 °C, so it is easy to mix with air and then burn itself to form a phosphorus fire. And because the average temperature is higher in summer, phosphorus fire (ghost fire) is more likely to occur in summer.

So why do some people say that ghost fire seems to chase people? This starts with the combustion mechanism of the phosphorus fire, because if there is no wind when the phosphine is burning, the phosphorus fire will stand still; if there is air agitation at this time, such as wind or someone passing by, causing the surrounding air to flow faster and pressure Smaller. Phosphorus fire will flow from places with high pressure (high concentration) to places with low pressure (small concentration), so the phosphorus fire will follow people, forming an illusion of chasing people.

In addition, the occurrence of phosphorus fire is actually a good phenomenon! Phosphine is actually toxic. If it accumulates too much, it may cause damage to the human respiratory and nervous system if someone inhales it accidentally. Therefore, the occurrence of phosphorus fire can help reduce the accumulation of phosphine!

Finally, when you see the phosphor fire in the future, you can stop worrying!

Extended Activities

Lab visit

  • SGS Hong Kong Limited
  • ALS(HK)

Competition

  • Secondary School Mathematics and Science Competition