Electrolysis of water (a few drops of universal indicator is added in water)

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Posted by Mr. Ricky Tsui | Posted in Chemistry, Integrated science | Posted on 18/03/2017

[DSE CHEM] How to memorise the inter-conversion between different organic compounds?

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Posted by Mr. Ricky Tsui | Posted in Biology, Chemistry | Posted on 12/08/2015

Hope this will help you abit!

[F1 IS] Steam engine + generator + light bulb

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Posted by Mr. Ricky Tsui | Posted in Integrated science | Posted on 11/06/2015

Slow motion:

 

Parts that you may be interested in:     (Source: Howstuffworks)

Keyword(s): burn, energy, energy change, energy convertor, fuel, light bulb, motor, steam engine, generator

[F3 IS/ DSE Chem] Compare the reactions of Ca and Mg

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Posted by Mr. Ricky Tsui | Posted in Chemistry, Integrated science | Posted on 08/05/2015

Reaction with cold water

Reaction with air (burning)

Keyword(s): air, calcium, calcium hydroxide, calcium oxide,cold water, hydrogen gas, magnesium,magnesium hydroxide, magnesium oxide,metal, metal hydroxide, metal reactivity series,oxide, oxygen, reaction of metal

[F1 IS / DSE CHEM] Water treatment plant – Filtration

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Posted by Mr. Ricky Tsui | Posted in Chemistry, Integrated science | Posted on 20/04/2015

Filtration is commonly used to remove insoluble impurities from a mixture.

Question:

In filter column, we often put small and fine substance on TOP (e.g. sand, activated carbon powder) and put large substances at BOTTOM (e.g. rocks, stones), WHY?:)

Let’s see:

DEMONSTRATION

 

REAL

Keyword(s): filter column, filtration, particle size, water purification

Distillation of Coke

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Posted by Mr. Ricky Tsui | Posted in Chemistry, Integrated science | Posted on 26/03/2015

Keyword(s): boiling, condenser, distillate, distillation, residue, simple distillation, solute, solution, solvent

[F1 IS] Properties of images under the light microscope

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Posted by Mr. Ricky Tsui | Posted in Biology, Integrated science | Posted on 04/03/2015

[DSE Chem] Equilibrium examples

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Posted by Mr. Ricky Tsui | Posted in Chemistry | Posted on 07/01/2015

Example (1) – Cobalt(II) chloride

Now, you are going to understand this …

1

 

 

233153586

 

 

 

 

 

 

 

 

 

 

 

 

Example (2) – Dichromate

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[DSE Chem] Polar and Non-polar molecules demonstration

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Posted by Mr. Ricky Tsui | Posted in Chemistry, Integrated science | Posted on 14/11/2014

Four liquids (from left to right): water, cyclohexane, acetone (propanone) and ethanol are placed inside burettes.

Once the tap is opened, a (negative) charged ruler is placed near the jet of liquid to see any deflection occur.

What can we conclude for the molecular polarity? (Is it polar or non-polar?)

1

 

 

Keyword(s): acetone, alkane, dipole, dipole moment, ethanol, hexane, hydrogen bond, non-polar, partial charges, polar, propanone, solvent, water

[DSE CHEM] Follow the rate of reaction between thiosulphate ions and hydrochloric acid

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Posted by Mr. Ricky Tsui | Posted in Chemistry | Posted on 10/10/2014

thiosulphate

Test for SO2(g) produced: turn wet pH paper from yellow to orange

Keyword(s): acidic gas, cross, hydrochloric acid, pH paper, rate of reaction, sulphur, sulphur dioxide, test for gas, thiosulphate

[F3 IS / DSE BIO] Rat dissection (digestive system)

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Posted by Mr. Ricky Tsui | Posted in Biology, Integrated science | Posted on 09/04/2014

Keyword(s): digestive system, rat dissection

[F2 IS / DSE CHEM] Bubbling (excess) carbon dioxide gas into limewater

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Posted by Mr. Ricky Tsui | Posted in Chemistry, Integrated science | Posted on 11/03/2014

8

Keyword(s): carbon dioxide, carbonate, hydrochloric acid, hydrogencarbonate, limewater, limewater test, marble, milky, observation, re-dissolve, soluble

[F2 IS / DSE CHEM] Universal indicators in daily life acids and alkalis

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Posted by Mr. Ricky Tsui | Posted in Chemistry, Integrated science | Posted on 04/03/2014

 

Look at the color change of universal indicator in different acids and alkalis in our daily life:

Keyword(s): acid, alkali, color change, domestic acids, domestic alkali, indicator, observation, pH, universal indicator

[DSE CHEM] Reaction between aqueous metal ions and alkalis

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Posted by Mr. Ricky Tsui | Posted in Chemistry, Integrated science | Posted on 25/02/2014

Precipitation between aqueous metal ions and alkalis (NaOH & NH3):

Mx+(aq) + x OH-(aq) –> M(OH)x(s)

Before reaction:

before

 

1. Metal ions + Sodium hydroxide solution (until in excess)

After excess NaOH is added:

after1

 

2. Metal ions + Ammonia solution (until in excess)

After excess NH3 is added:

after2

Keyword(s): alkali, base, complex, complex ions, hydroxide ions, metal ions, precipitation, re-dissolve, reaction rate

[F3 IS / DSE PHY] Convection

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Posted by Mr. Ricky Tsui | Posted in Integrated science, Physics | Posted on 22/01/2014

Here is a demo for showing the air flow when convection happens.

In convection, hotter gas rises and cooler gas sinks and replaces the hotter gas.

Therefore heat can be transferred from a hotter place to a cooler place by this air flow (convection).

Keyword(s): air flow, convection, heat transfer, hot air, rise

[F3 IS / DSE CHEM] Thermal decomposition of calcium carboante by strong heating

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Posted by Mr. Ricky Tsui | Posted in Chemistry, Integrated science | Posted on 21/01/2014

Keyword(s): break down, carbon dioxide, carbonate, decomposition, heat, limestone, limewater, milky, planet earth, thermal decomposition

[F3 IS / DSE Chem] Test for chloride ions in an aqueous solution

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Posted by Mr. Ricky Tsui | Posted in Chemistry, Integrated science | Posted on 21/01/2014

In case we want to test for the presence of chloride ions in an aqueous solution, we can use the precipitation method.

Ag+(aq) + Cl-(aq) –> AgCl(s)

Ag+(aq) is from silver nitrate solution (ALL nitrates compounds are soluble in water)

Cl-(aq) is from the sample (if the aqueous sample contains chloride ions)

Test methods:

Adding acidified silver nitrate solution (WHY do we need to ACIDIFY the silver nitrate solution? See below)

Positive result:

White precipitate is formed

From the video above, carbonate ions will also form white precipitate with silver ions:

Ag+(aq) + CO3^2-(aq)–> Ag2CO3(s)

This will affect the accuracy of test because we do not know the white precipitate is due to presence of carbonate ions or chloride ions.

From the video above, once we added some dilute nitrate acid into the test tubes with white precipitates.

The test tube with Ag2CO3(s) turns to colorless as Ag2CO3(s) reacts with HNO3(aq) to form soluble AgNO3(aq):

Ag2CO3(s) + 2HNO3(aq) –> 2AgNO3(aq) + CO2(g) + H2O(l)

Therefore, if we want to test the presence of chloride ions in a solution, ACIDIFIED silver nitrate solution will be used.

Keyword(s): chloride, ocean, planet earth, qualitative analysis, silver chloride, silver nitrate, test for chloride

[F3 IS / DSE Phy] Total internal reflection

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Posted by Mr. Ricky Tsui | Posted in Integrated science, Physics | Posted on 03/01/2014

Total internal reflection

is a phenomenon that happens when a light ray strikes a medium boundary at an angle larger than the critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is greater than the critical angle, the wave cannot pass through and is entirely reflected. The critical angle is the angle of incidence above which the total internal reflectance occurs.

Application of total internal reflection – optical fiber (光纖)

A technology that uses glass (or plastic) threads (fibers) to transmit data. A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves.

Advantages of Optical Fiber

Less expensive

Higher carrying capacity – Because optical fibers are thinner than copper wires, more fibers can be bundled into a given-diameter cable than copper wires. This allows more phone lines to go over the same cable or more channels to come through the cable into your cable TV box.

Less signal degradation

Keyword(s): critical angle, light, optical fiber, refraction, total internal reflection

[F3 IS / DSE Phy] Mirage by curved mirror

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Posted by Mr. Ricky Tsui | Posted in Integrated science, Physics | Posted on 02/01/2014

Can you see a pig and a marble on the dish?

Can’t you catch the pig and the marble? 🙂

They are the real image! a kind of mirage formation

Keyword(s): image, mirage, mirror, real image, reflection

[F3 IS / DSE PHY] Refraction of light (Snell’s Law)

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Posted by Mr. Ricky Tsui | Posted in Integrated science, Physics | Posted on 19/09/2013

Refraction (Snell’s Law)  states that the relationship, sin i / sir r is a constant. Below shows you a good video for demostrating the law stated above (Source: YouTube Rosa Brígida)

Part A: light travels from air to glass

Part B: light travels from glass to air

Keyword(s):  light, refraction, Snell’s Law

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