All the ‘miracles’ in the world to help you during exams

Sorry peeps,

I have not been writing new posts, as I am busy with the exam preparation for the students. Lots to catch up, follow up and to mark.

But here’s a tip for the examination:-

Say you have done all the preparation you needed, ( don’t worry, I believe you have if you have been spending at 6 hours each week for Chemistry), before you enter the examination hall, give a big smile to yourself, breathe out hard all the worries and butterflies you have, walk towards your table, sit down and relaxxx….

I cannot tell you how important the state of mind is for any examination or tests in this world.

Once you learn how to control that emotion and that mind of yours, you will see the wonders it can do to you in life!!

Some will take Essence of Chicken, others might take Cod Liver’s Oil or supplements like Gingko pills to boost the brain. AND it works!

In my school days, I take Essence of Chicken, now I am giving my students Gingko pills. Bear in mind though, Gingko is not a ‘miracle’ pill — one still needs to put in hard work for results. Gingko is just meant to keep the mind alert and not have the ‘mental block’.

(Contact me if you need more information about the supplements)

Gingko

And Yes! Proper regular sleeping hours/pattern and wholesome nutrition are all part of the gameplan as well. Eat well, and not MacDonald’s all the time will help boost the memory and brain activity too.

If you need to, go do a 20-30min run every other day. It improves blood circulation and so more blood goes to the brain.

In this period, the brain is working so hard, it is under oxidative stress, many free radicals are formed- you may not realize it but it is happening. Take fruits with high antioxidant levels like blueberry and grapes. Google and you will know more.

So good luck everyone and share with me what are some of your exam techniques.

As always, if you have any questions, post them here or email me.

Adieus. Yuyan

Kinetics – graphical work

After teaching for more than 5 years, I always feel that kinetics is one of the easiest chapters to score, provided one does not make careless mistakes!

Remember fundamentals are important!!

The basics of Kinetics: remember…
1) Rate = change of concentration / time
2) Rate = k[A]^n (where A is reactants, n is order of reaction)
3) units of rate = concentration units /time (eg, moldm-3s-1 , molm-3min-1 etc)
4) orders of reaction is an integer with values 0,1 and 2 only

Graph work:

ZERO ORDER REACTIONS
- Concentration vs time graph = downwards straight line. Gradient gives you rate. (from the equation Rate = change of concentration / time)
- Rate vs Concentration = flat straight line. Gradient gives you k. (from the equation, Rate = k[A]^n)
- Essentially, rate is INDEPENDENT of concentration, rate = k

FIRST ORDER REACTIONS
- Concentration vs time graph = downwards parabolic curve. Gradient gives you rate. (from the equation Rate = change of concentration / time)
- Rate vs Concentration = increasing constant straight line. Gradient gives you k. (from the equation, Rate = k[A]^n)
- Essentially, rate is DIRECTLY PROPORTIONAL to concentration
- Rate constant, k, is INDEPENDENT of concentration
- Concentration/time graph has a half-life that is constant, hence, we have the equation, t 1/2 = ln2 /k

SECOND ORDER REACTIONS
- Concentration vs time graph = downwards curve. Gradient gives you rate. (from the equation Rate = change of concentration / time)
- Rate vs Concentration = upwards curve. Gradient gives you k. (from the equation, Rate = k[A]^n)
- Essentially, rate is NOT PROPORTIONAL to concentration
- Rate constant, k, is DEPENDENT of concentration
- Concentration/time graph has a half-life that is NOT constant, dependent on initial [A]
- Half life t 1/2 = 1/k[A]

TIP:
When finding half-life, note the y-axis.

If it is concentration of REACTANTS against time,
determine half-life at 1/2 [A], 1/4[A] and 1/8[A], where [A] refers to the INITIAL concentration of reactant.

If it is the concentration of PRODUCTS against time,
determine half-life at 7/8 [B], 3/4 [B] and 1/2[B], where [B] refers to the MAXIMUM concentration of products formed (if it can be possibly found from the question)

The trick with Chemical Energetics

Chemical Energetics is the study of energy changes in chemical reactions. Energy cannot be created nor destroyed; it can only be converted from one form to another.

Change : You can have either negative energy change ( net heat given off = exothermic), no change ( no net heat given off or taken in = equilibrium) or positive energy change (net heat taken in = endothermic)

Enthalpy Change ∆H is the net heat change of a given reaction.

The trick with Chemical Energetics is to be able to define exactly the respective enthalpy changes AND be able to convert the definition into equations with STATE SYMBOLS. (state symbols are EXTREMELY IMPORTANT and essential to include in questions and answers).

What are the definitions of ∆H that you have to know:

1) ∆H of formation
2) ∆H of reaction
3) ∆H of combustion
4) ∆H of hydration
5) ∆H of atomisation
6) ∆H of vaporization
7) ∆H of fusion
∆H of sublimation
9) ∆H of solution
10) Lattice Energy
11) Ionization energy
12) Electron Affinity

13) Define Hess’ Law

Born-Haber cycle is just a method that relates to lattice energy of ionic compounds.

So the above 12 definitions, are you able to write them into equations?

The importance of Chemical Bonding and Structure of Compounds

Today I will like to emphasize about the importance of this topic. I believe many of you know this chapter relatively well. At least you understood the gist of the topic.

Like you know what is a metallic bond, ionic bond and covalent bond. (I hope you do).

But what is more crucial is the ability to fully understand the How, Why and Where these bonds and formed.
Also, the important KEY PHRASES to use when describing the bonding and structure of ANY compounds, so that during the exams, your answers are 1) structured 2) to the point 3) accurate.

3 important factors in answering any question in this chapter.

Now when we move onto the structure of compounds, this starts to become complicated as now we have another ‘bond’ to consider. However, to make things clearer, I prefer to call these ‘bonds’ —- FORCES, more accurately called ‘Intermolecular Forces of Attraction’ (IMF for short).

IMF in compounds may or may not be same as bonds between atoms in a single molecule. Hence, students should learn to differentiate the two terms very well.

Hope this tip has helped you in approaching revision for this chapter.

All the best!
–Yuyan
( SMS: 9447-8193 for individual or group consultation)

16-weeks to A level Chemistry Paper 3

Paper 3 of A level Chemistry is one of the papers Chemistry students fret most! Because each question is worth 20 marks and topics tested can be from any chapter throughout the syllabus.

On average, a student should spend no more than 30minutes on each question, in order to finish the paper ACCURATELY within the 2-hour time allocated.

Now that is a BAD strategy, as it leaves NO TIME for checking through.

Based on experience, I realized that the checking-through process actually helps in scoring more marks, as you go through your answers again,  FINE-TUNING your answers and diagrams.

Fine-tuning is always an important but over-looked process.

So ideally,  spend no more than 25minutes on each question ,so that you are left with 20minutes to take a breather, collate your answers sheets and check-through your work at least once.

With just 16-weeks left to Paper Three, it is time to start doing past-years papers or at least a revision plan in place.

Be sure to solidify your foundation and understanding before handling trickier questions. It will be good if you can form a small study group of 4 ( friends who are serious with their work, of course) and revise together.

16-weeks/4-months: It is not too late still as long as you start making plans NOW.

YuYan

I am still available for intensive revision coaching with individual or group of 4 on weekdays and Sundays.

Welcome!

Welcome to CambridgeChemistry’s blog.

I have now finally achieved my dream of coaching a group of A level students who require help and guidance for A level Chemistry. It gives me great pleasure to interact with the young adults, as we both learn from each other.

Going through the same 2-year Junior College in Singapore, I understand perfectly the agony, and the frustrations one has when preparing for the A levels.

I am proud to have device my own studying method, more importantly, exams techniques and learning styles that have put me through my studying years effectively.

So I welcome all of you from all levels of learning to experience my fun, heart-lightening teaching approach.