Cya guyz soon. Enjoy watever is left of the hols!

Accolades IV

Yoz everyone,

After a year of hardwork, we have survived this year.

Let's celebrate the success together!

Accolades III

Hi, all,

This is the ranking for the CA.

Congratulations to all. Do work harder for the coming EOY. Remb our aims!

Application of Redox - Photochromatic lens

Hi,

You must have noticed that some of your friends wear glasses whose lenses change opacity under different lighting.

Nope, they are not from Hogwartz (unlike me, haha). This is the work of Redox Chemistry.

Basically, in their lenses, called photochromic lenses, silver chloride (AgCl) and copper(I) chloride (CuCl) crystals are added during the manufacturing of the glass while it is in the molten state and these crystals become uniformly embedded in the glass as it solidifies.

One characteristic of silver chloride is its suscepitibility to oxidation and reduction by light as described below.



The chloride ions are oxidized to produce chlorine atoms and an electron. The electron is then transferred to silver ions to produce silver atoms. These atoms cluster together and block the transmittance of light, causing the lenses to darken. This process occurs almost instantaneously. As the degree of "darkening" is dependent on the intensity of the light, these photochromic lenses are quite convenient and all but eliminate the need for an extra pair of sunglasses.

The photochromic process would not be useful unless it were reversible. The presence of copper (I) chloride reverses the darkening process in the following way. When the lenses are removed from light, the following reactions occur:


The chlorine atoms formed by the exposure to light are reduced by the copper ions, preventing their escape as gaseous atoms from the matrix. The copper(I) ion is oxidized to produce copper(II) ions, which then reacts with the silver atoms as shown.


The net effect of these reactions is that the lenses become transparent again as the silver and chloride atoms are converted to their original oxidized and reduced states.

Q. Identify the oxidising agents and reducing agents in both Eq 1 and 2.

Adapted from Oxidation/Reduction by Kapi'olani Community College.

Thanks!

Yoz guyz,

Thanks for all your cards, gifts, words of encouragement:



Enjoy the Sept hols, but dun forget to mug for you-know-wat-is-the-most-impt-subject.

Be prepared for presents from me via emails.

Cheers,
Mr Koh

Nitric Acid - A special one

Yoz,

We have been working on Acids for some time now.

What we know is that acid reacts with reactive metal (e.g. Zn, Mg, Ca) to form salt and hydrogen. The unreactive metals (e.g. Au, Cu) do not react with acids.

However Cu does react with nitric acid. Why? Because nitric acid is an oxidising agent as well. Read more about the nitric acid here.

Some terms you would be familiar would be: strong acid, acid concentration, etc.

You could also read about the 'strongest' acid which scientists have made. (see here) How is this acid contradicting what we discussed in class?

Carborane, part of the world’s strongest acid. [Atom color code: orange = boron, gray = carbon, green = chlorine, white = hydrogen.] Picture from ScienceDaily.com

Accolades II

Hi, all,

This is the ranking as of present (70% of RP CA and 37.5% of RA CA is included in computation).

Congratulations to all. Let's work hard to make the list longer!

Methane - Solution to the Rising Fuel Cost

Hi,

Recently, the local paper reported that more of our cars are being converted to ones driven by CNG (compressed natural gas). For those who still do not know what CNG is chemically, it is methane. The driving force to convert is that CNG is much cheaper when compared to the petrol. However, the price of CNG is also rising. Why? Think about it.

Actually the ground is not our only source of methane. We can get it from guts of cows, sheep, and maybe you!

In the 1960's, scientists found high levels of methane near the ocean’s oxygen-rich surface, which is unusual. Why is it unusual? Don't tell you now.

Now they have uncovered the reason behind this. To know more, read this.

Who's interested in working on this for RE? Maybe we could be the next millionair?!

Super Atoms

Hey. So long never blog liao.

Well, since there's really not much new research in the area of Mole Concept, let me post you a question regarding this topic:

Why was there only 1 Avogadro? (see Comments for answer and souce.)


Anyway, there is now such a thing call super atoms. It was found by researchers that metal atoms will form clusters in vapor phase and behave like another element. Want to find out more, read this.

Cya around.

Picture from ScienceDaily.com

Lavoisier

Yoz,

The hols is coming to an end soon.

Btw, do remember to submit your Lavoisier Assignment when school reopens. And don't be like someone who is trying to get the answer from yahoo.answer. And the person who replied is NOT me. =)

Anyway, here's one good book you might want to read:

A World on Fire - A Heretic, an Aristocrat, and the Race to Discover Oxygen by Joe Jackson.

It talks about Lavoisier and another scientist Joseph Priestley.

Enjoy!

Picture from Lukeman.com

Mole Concept - Word Search

For those who are too boliao, you can test your understanding of mole concept here!


Puzzle from Oklahoma State University
Enjoy!

p.s. why is the molar gas volume different from ours? I thought it should be 24 dm3? Do not be confused ok!

Balancing Equations

Yoz,

Here's some websites for you to practice the balancing of equations.

You get to check if you have gotten it right immediately.

Notes and Exercise: http://richardbowles.tripod.com/chemistry/balance.htm
Exercise: http://funbasedlearning.com/chemistry/chemBalancer3/default.htm
Exercise: http://www.chem.vt.edu/RVGS/ACT/notes/scripts/bal_eq1.html


Picture from Edventure.com

Accolades

Hi, all,

This is the ranking as of present (38% of RP CA and 25% of RA CA is done).

Congratulations to all.

Chemistry - It's so Fun

Hi,

Still can't distinguish elements from compounds after mugging for hours now? Don't fret, go take a look at Elementeo, a card game created by a 14-year old CEO. (Related article here)

Take a break from all the mugging.

Best wishes!

Picture from Elementeo.com

Announcement: CCT 1

Yoz,

The real test has arrived. The CCT 1 for Chemistry has been scheduled to be done on 14 Apr (Mon).

The topics tested are:

- Particulate Nature of Matter
- Experimental Design and Purification Techniques
- Atomic Structure (including spdf subshell)
- Chemical Bonding (only ionic and covalent bonding)

Ganbatte!


Picture from Art.com

RA students to refer to the RA Forum for more details of your CCT 1 which would be held on the same day.

Am I hearing you rite, Ionic Liquid??

Hi, guys,

As we have studied in our class, ionic compounds are usually solid. Why?

Long pause.... cos ionic bonds are strong rite!!! Because ionic bonds are strong, large amount of energy is needed to break these bonds in order to turn the ionic solid into liquid state.

Now, not all ionic compounds have high melting point. There are actually things called 'ionic liquids'. As the name implies, it is an ionic compound but is also in liquid state.

How is that possible? Again, it has to do with the strength of the ionic bond. In ionic compounds where there is a large difference in the size of the ions (i.e. one big ion and a small ion), the ionic bond would be weaker. Hence, this results in the compound existing in liquid state under room temperature.

Now, these ionic liquids are useful stuff. One of the latest application is to use it as a substitute for mercury and alcohol in thermometer.

Read this for more info.

Enjoy!

Picture from Chemical Technology

Diamond vs Glass

Hi, guys,

Thought about this question on the way to school this morning....

Since you are currently working on the 'Structure and Bonding' e-learning (or at least I imagine you are), you would know that Diamond is hard because all C atoms are ______ and _____ bonded to each other. Since covalent bonds are _______, _____ amount of energy is needed to break them and hence diamond is hard.

Now, we also know glass has a similar structure, though not exactly. Now, the question is, why diamond is hard while glass shatters?

Interesting question rite? Do discuss in the comments....

What to do?

What to give for extension?? Haiz.... Primary school topics really nothing to talk about... haiz...

Bohr's Atomic Model

Hi, everyone,

As we have discussed in class, Bohr came up with his model of the atom through experimentation.

Through his experiments, he found that atoms only absorb certain wavelengths of light (i.e. certain energy). This gives evidence that electrons can only occupy certain energy levels (which we now call shells). The energy carried by light of these wavelengths corresponds to the energy gap between the shells.

Should there not be shells (discrete energy levels), any wavelength of light would be absorbed by the atom to excite its electron to any energy state.

Here's a video which I think is rather useful. It talks about the emission spectrum, which shows that light emitted by excited atoms (i.e. atoms with their electrons promoted to higher energy shells) are also of particular wavelength and expectedly, this energy corresponds to the gap between the shells.

Enjoy!



For the learners who prefer reading, this website is also quite simple to understand.

Test for Weeks 9 and 10

Hi, everyone,

This is an announcement about the tests coming up:

1. Week 9:

SPA Skill A (Written test)
Date: 29 Feb
Time: Immediately after school
Venue: Auditorium

2. Week 10:

Atomic Structure (Open-book assessment)
Date: Lesson 1
Venue: Respective classrooms

Mug hard! Remember, all to get 4.0!!

The Mystery Begins

Yoz, ppl,

About two months have passed since we embarked on the journey of conquering the subject of Chemistry together.

To some, the subject seems Cheem... (for our international scholars, 'Cheem' = profound").

To others, it is just a mystery that you would like to solve.

Whatever the case, I hope this blog would serve as a point for you to discover more about the topic.

Let's dive into our Cheem Mystery!


Picture taken from HawaiiArt.com

p.s. anything wrong with the picture?