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Alcohol Concept Map

Mr Khemistry

Alcohol Concept Map

Alcohol concept map

This is the 4th installation of a series of organic concept maps. Part 2 phenol will be uploaded next week, watch this space!

Free free to print out for personal use but do not distribute 🙂

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Alkene Concept Map

Mr Khemistry

Alkenes Functional Group Concept Map

Alkenes concept map

You can use this series of organic concept maps to familiarize yourself with the various transformations of the functional groups.

Using this format, we can also practice drawing skeletal structures for organic molecules.

You can download this and print it out for your own usage, not for distribution please 🙂

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Kinetics – The Big Idea by Mr Khemistry

Mr Khemistry

Kinetics

Kinetics is the study of speed/rate of a chemical reaction.

Definition: Rate of reaction is the change in concentration of reactant or products over time.

Question: How do we know what’s the change in concentration of reactant or products?

Ans: We have to MONITOR it.

Question: How do we monitor it?

Ans: Look at the reaction equation, what has changed from left-hand side (LHS) to the right-hand side (RHS)? We can monitor colour intensity (colourimeter), volume of gas evolved (downward displacement of water/gas syringe), loss of mass (mass balance), change in pressure (manometer), electrical conductivity, pH (pH probe, titration) etc.

Image result for colorimeter

Colorimeter

Main Product

Manometer

An important term in this chapter is “Order of Reaction”. We can only determine the order of reaction with respect to a particular reactant through experiments. Note: Order cannot be determined from the chemical equation.

Consider this chemical reaction:

A + B -> C + D

To find the order wrt reactant A, we will have to conduct expts keeping B constant and varying [A] to monitor the effect on rate. Likewise, to find the order wrt B, we will need to keep A constant and vary [B]. One of the ways to keep the other [reactant] constant is to make it in large excess.

To find out more about kinetics or other topics, come join our weekly JC tuition classes at bukit timah shopping centre.

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Life skill

Mr Khemistry

Life Skill

Let me start with a little anecdote. What if i tell you i have a fully paid vacation for you and your whole family to Hawaii, for 10 days. This offer has no catch except that you must leave tomorrow morning. Would you go? I bet most of us would scramble to delegate our tasks to do for the next 10 days just so that we can go for this trip no?

And since we can do that, why don’t we increase our productivity everyday just practising this hypothetical situation? Imagine packing all you can do in 10 days into just 1 day. And do it repeatedly for the next 30 days. Just how much can you get done in this month?

The truth is, our capacity is a mental state of mind. All limitations are self-imposed. Men can do whatever we set our minds to do. Nothing that we PURPOSED to do (set a goal to achieve) will be impossible.

So why is this important for us to realize? Because it is a life skill. Students often lament the lack of time. I believe it’s more a lack of purpose, or goals. Why do some students (even adults) find it hard to get up from their beds in the morning? Always feeling lethargic and tired. Procrastinating on basically anything and everything? Distracted by social media, tv etc. Again, it is due to the lack of a big enough goal/purpose.

If we set goals that affect us emotionally, that excites us, galvanize us, would we be distracted easily? Or struggle to get out of bed? Probably not. Hence, set goals. Don’t procrastinate. Move! Take action and watch your life change. You’re welcome 🙂

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Energetics Thermochemistry

Mr Khemistry

Energetics Thermochemistry

Energetics is such a broad topic students sometimes have difficulty understanding what the question is asking for. This post aims to help build a mental shortcut for students to “funnel” the question into broad question types. Thereafter to quickly apply the thought process for solving it.

In the picture below, you see the four broad question structures on the left. On the right side is the approach to solve certain types of questions. Additionally, there are also acronyms to help students remember the sequence of answer, e.g. F.A.I.L for Born Haber Cycles and BE.R.P. for bond energy.

Energetics Question Structure

Energy cycles can only be done well if you have a good grasp of the common definitions of different enthalpy change. Point 5 on the left shows the three main components of definitions for enthalpy change.

Energy level diagrams are simply a special type of energy cycle where the arrows point upward for endothermic reactions and downwards for exothermic reactions. Learn how to construct energy level diagrams quickly in our weekly classes. It is easier to learn how to construct energy cycles/levels when you can see how other students do it. Moreover, we can also see what kind of mistakes are commonly made.

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More Energetics!(Born Haber Diagram)

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Cells of recognition

Mr Khemistry

Cells of Recognition

All of us have brain cells that helps us make sense of our environment. From the second we blink-open our eyes when we wake. These cells of recognition have been built way back when we were infants. Day by day, week by week, month by month and year by year. We are able to go through the day, sometimes without thinking much about what we’re doing because of them. Some experts call this habit. But before we can form a habit, we do need to think about what we’re doing. Only once we have made sense of the action, then we do it repeatedly WITHOUT thinking about it.

Why am i talking about this?

Because i believe the reason why many students do not do well with Chemistry (or any subject) is due to the fact that they don’t recognize this. Some do and they actively build cells of recognition as they are studying. That is the reason why we do Ten Year Series. To build cells of recognition. To see how Cambridge phrased the questions SO THAT we can recognize the pattern and give the correct answer. What we should try to do is to inculcate this routine into our daily studying.

How many of you realized that the duration that you have to learn more complex concepts is getting shorter? In primary school, you had six whole years to learn and build those cells of recognition. For secondary school, you had four whole years. However, in Junior College, you have slightly less than two years to make sense of the most abstract concepts!

Is it any wonder that students are struggling? Does it seem strange that you are failing tests where previously you have always done well? The  change in teaching and learning environment from classroom teaching to lecture/tutorials. You were expected to hit the road running. Many students find themselves wondering what happened. The truth is, even though humans are extremely adaptable creatures, we still need time to process changes and to adjust our thinking.

In primary school, we had six years to adjust to the concept of “School”. At secondary level, we had four years to make sense of many subjects at introductory level. For Junior College, we have slightly less than one and the half years to complete the “advanced” syllabus. To adjust to the new system of lecture/tutorial, for some, it’s also a period where they are exploring romantic relationships. With so many changes going on at the same time, it’s no wonder many youths cannot cope with their studies load.

How do we navigate this tumultuous times? By actively thinking and planning our time weekly, having a good overview of what we are doing. It helps when you can build up a routine for quickly reviewing and reflecting on the boatload of new content every week. The students who can adapt quickly to the changes and settle down to building new cells of recognition will do well. Those who take a long time to adapt will show symptoms, such as late-coming and lethargic behavior in class.

It’s vitally important that students make full use of their weekends to recap what they have learnt through the week. The many requirements imposed on them throughout the week can drain their energy, causing them to be too tired to revise at night. Those who force themselves to stay up late to study more often then not, put too much stress on themselves. Usually this results in lowered alertness and attentiveness during lesson time, which hinders their ability to take in new information. Not having adequate rest during the weekdays is detrimental to  learning.

In a nutshell, build routines quickly, then build cells of recognition. This process will allow you to quickly adapt to JC life and get down to learning the new concepts.

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Chemical Equilibrium Summary Table

Mr Khemistry

Chemical Equilibrium Summary Table

The qualitative aspect of Chemical Equilibrium can be summarized into the table below.

From the table, we can see that changes in concentration, pressure and catalyst does not affect Kc/Kp. The only factor that does affect equilibrium constants is temperature. Also, we would need to know whether the forward reaction is endo or exothermic to predict the effect temperature change will have on it.

Note that increasing temperature increases both the rate of forward and backward reactions. However, the rate of the endothermic reaction will be increased more than the rate of the exothermic reaction.

If the enthalpy change for the reaction is zero, temperature will have no effect on the equilibrium. Similarly, if the reaction has the same number of moles of gaseous particles on both sides, pressure will have no effect on it.

An interesting point to note is catalysts have no effect on position of equilibrium and equilibrium constant. The only effect it has is to increase the rate of both forward and backward reactions to the same extent.

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Relationship between Kc and Kp – Chemical Equilibrium

Mr Khemistry

Relationship between Kc and Kp – Chemical Equilibrium

I was updating the chemical equilibrium notes this week and thought it would be good to share this with all of you.

Didn’t know how Kc and Kp was related and i was stumped by a question about 10 years ago when i was still teaching in a JC.

Relationship between Kc and Kp

The main idea is to use the ideal gas equation to substitute partial pressures in concentration terms.

Once you got it, it’s quite easy to remember 🙂

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