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Black GAMSAT Friday…

I saw this date approaching…I thought..no, surely not…but of course. Like a crazed vengeful zombie, there it was, that email from ACER, sitting in your inbox, with the date stamp Friday the 13th.

Only the Australia Council for Educational Research (aka ACER, aka creator of GAMSAT, aka the bane of a med-student wanna-be’s life) would be so cruel as to release GAMSAT results on Black Friday!

friday13

So here I have 5 tips for those who were LUCKY, and 5 tips for those who were UNLUCKY.

First up,

FOR THE UNLUCKY:

  1. Cry, scream, punch something (just not someone). It’s been a long, arduous process, you worked so hard and it’s really tough to have that end in disappointment. Then pull yourself together, reassess your life, dig deep and make the decision whether to give it another red hot go, this time with a whole lot more experience under your belt.
  2. Think about what you gained from the process. Now you know what it’s like to do 6 hours of exam in one day, and you know how you reacted under pressure, and whether you need to work on your timing, or question order strategy. Find out how to NOT be another GAMSAT crash test dummy.
  3. Where did you struggle? If you had trouble with all the graphs, or couldn’t do the maths quick enough, you’re not alone. Maybe it’s time to get back to basics when it comes to graphing, and if you have the right approach, you really can get over your fear of maths.
  4. What did you do right? Perhaps you nailed the essay section (because you read this post!) but need to work on your organic chemistry. Check out Organic Chemistry for GAMSAT. Where to start?
  5. If you’re feeling down and out- try not to be too hard on yourself. The GAMSAT is HARD. And super competitive. You did an amazing effort just to make the commitment to sign up for this gawd-awful test and sit through it! Check out our Top 10 tips for GAMSAT to see if there’s anything that might help you, should you decide to give it another shot!

FOR THE LUCKY BASTARDS ONES:

  1. Be super proud!
  2. Call your loved ones and thank them for putting up with you for the last year while you either a) slept with your text book, b) complained at how sadistic the GAMSAT is and how none of it is relevant to getting into med anyway, c) were a human jitterbug for the last 6+ weeks while you waited for the results to come out!
  3.  Have a well deserved party night off! Whether that’s a night out on the town, a romantic dinner for two, or a movie night with popcorn and chocolate. You’ve earned it!
  4. Call a friend who wasn’t so lucky. They probably worked just as hard as you, but it just didn’t come together on the day. We shouldn’t have to remind you not to #GAMSATGLOAT. Send them this article about Why they should embrace winter for GAMSAT study.
  5. If you were a cbsquared student, please get in touch and share the good news! Then you’ll need to start thinking about your interview process and decide what your uni preferences are. Good luck, and well done!

Well done to everyone, and remember to please get in touch if you need any ideas or advice for any stage of your GAMSAT journey.

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Organic Chemistry for GAMSAT: where to start?

An area of GAMSAT Section III that people tend to get a little worried (or let’s just be honest, completely freak out!) about is Organic Chemistry.

In my opinion, with a good knowledge of the language of O-Chem, and good use of pattern recognition skills there’s no reason why most candidates can’t do really well on these questions. In fact, I’ve often said that organic chemistry gives you your best bang-for-buck when it comes to study to increase in GAMSAT score ratio.

So, here’s my three steps to getting a good start on Organic Chemistry questions.

1. Learn some basic functional groups.

I’m not a big fan of learning by rote, but having a small repertoire of functional groups at your disposal will definitely help with Organic Chemistry questions, in particular the speed at which you can digest and deconstruct the stimulus.

Check out these online functional groups flash cards to really nail it!

 Functional Groups Flashcards
Click to use the flashcards

 

It would be helpful if you knew how to draw and recognise the following functional groups: alkane, alkene, alcohol, aldehyde, ketone, carboxylic acid, ester, halide/haloalkane, amine, amide, benzene/aromatic ring. Those taking the cbsquared Chemistry course will find a summary of these functional groups including structural formula, condensed structural formula, name/common name, prefix/suffix and an example as a resource document.

 

2. Be able to name molecules using IUPAC nomenclature

Again, not a fan of rote learning, but you must be able to apply IUPAC nomenclature to name and draw molecules in order to answer questions quickly and effectively. The Organic Molecule Game (OMG) will really scare you into naming organic compounds quick smart. There’s a mad professor and a zombie to really increase the sense of urgency. Bonus.

OMG
Click to play
OMG mad professor
Click to get scared

 

3. Understand reaction maps and pathways to solve chemical reactions

This is where rote learning chemical reactions WILL NOT HELP YOU. You WILL receive a reaction that you’ve never seen before in the GAMSAT, probably with functional groups you’ve never seen before either. The trick is to be able to use pattern recognition skills to deconstruct the reaction given in the stimulus, and then apply to your particular example to get the answer.

For example, you’ll probably be given a general reaction sequence in the stimulus, then you’ll be asked to give the products of a similar reaction, with the same functional groups involved. You should then rewrite the general equation given, using your specific molecules, to ascertain the structure of the product. The basic backbone of the compound (or functional group) will be the same, here’s when you use your pattern recognition skills to recognise where the key functional group is, and how it has changed as a result of the reaction taking place.

Check out the “Master Organic Chemistry” site for a great blog post with some examples and work through. Below is a reaction pathways map from their blog, similar to what is included in the cbsquared Chemistry for GAMSAT course, in the resources section.

reaction-map2
Click to read the blog post

 

Please note: You will not be given a reaction pathways map in the GAMSAT. BUT you will be given a general reaction, or a few reactions, as part of the stimulus for the question. If you know how to use a reaction pathway map, you will also know how to use and interpret a reaction given to you in GAMSAT stimuli.

Good luck! If you need more practice, the cbsquared GAMSAT for Chemistry attendance or online course could be for you.

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Top 5 Websites for Inspiring Reading (& GAMSAT Section II fodder)

Our busy lives, the 24 hour news cycle, the dynamic, often fleeting interaction and exposure we have to news and information and even with those around us – it’s hardly conducive to thoughtful pondering or philosophical contemplation.

When we are busy, tired, rushed…even friendly banter or debate in the form of a well constructed argument is often put in the “too hard basket” and exchanged for small talk.

And yet, a large part of the GAMSAT Section II requires a written demonstration of not only your ability to absorb and understand deeper issues, but the capacity to present an argument, or at least demonstrate your own stance or opinion on a particular topic or theme.

Rather than set yourselves the near impossible task of reading every Man Booker Prize winning novel for the last 20 years, or TIME’s top 100 Novel’s of all time, I suggest a less arduous approach, something more intrinsic, that can become a daily habit in your life.

The following websites have published some of the most fascinating, thought provoking and sometimes controversial articles or essays I have read.

I’ve listed my top 5, in alphabetical order, below. I include a sample article from each to get you started.

Follow them in your aggregator of choice, and you won’t be able to resist reading them as they pop up.

Enjoy 🙂

aeon

 1. Aeon

Aeon is an online magazine that “asks the biggest questions and finds the freshest, most original answers, provided by world-leading authorities on science, philosophy and society.”

When I started reading Aeon, it published longform essays “explorations of deep issues written by serious and creative thinkers.” now it also has another three channels: video, short opinion section and interactive conversations.

I’ve chosen this article with the “C” word because it I feel it has relevance for anyone wanting to move into healthcare. It encompasses the entire body (pardon the pun) of the medical treatment process right from the very start- the research question, the actual medical research, the funding, the implementation, and then the bureaucracy that has the power to help and hinder outcomes for people’s lives. Interwoven through it all, is hope.

Follow aeon: WebFacebook | Twitter

Hand picked for you: Why are people still dying of cancer?

 

brainpickings

2. Brainpickings

A blog…. that’s not just any blog. Written by the amazing Maria Popova, bulgarian self-proclaimed “reader, writer, interestingness hunter-gatherer, and curious mind at large.” The blog gets close to 2 million hits a month, the Facebook page has almost 4 million followers. Read her articles for a week and you’ll see why.

“If something interests me and is both timeless and timely, I write about it. Much of what is published online is content designed to be dead within hours, so I find most of my material offline. I gravitate more and more towards historical things that are somewhat obscure and yet timely in their sensibility and message.”

I love science philosophy and I especially love when Carl Sagan talks science philosophy-hence my hand picked article below.

Hand picked for you: Carl Sagan on Science and Spirituality

Follow Brainpickings: WebFacebook | Twitter

 

conversation

3. The Conversation

Thank goodness for The Conversation. Proud to say it was launched here in Australia, it is an independent, not-for-profit media outlet that uses content sourced from the academic and research community.

That’s real researchers doing real research writing this stuff. There’s plenty of comment on news and current affairs (which is not a focus of the other websites in this list).

Most of the articles I read on The Conversation are quite academic and at times dry, so I’ve listed this one as a bit of an antidote, or at least a reminder that a good story is good for the soul -so says science 🙂

Hand picked for you: ‘Remember when we…?’ Why sharing memories is soul food.

Follow The Conversation: WebFacebook | Twitter

 

nautilus

4. Nautilus Magazine

Nautilus is an online and print science magazine that “combines the sciences, culture and philosophy into a single story.” Issue topics have included human uniqueness, time, uncertainty, genius, mergers & acquisitions, and feedback.

It was only launched in 2013, but since then has won some pretty prestigious awards, including a Webby Award in 2014 for best science website and in 2015 won two National Magazine Awards (aka “Ellies”), for General Excellence (Literature, Science and Politics Magazines) and Best Website.

Nautilus has also had two stories selected to be included in 2014 edition of The Best American Science and Nature Writing.

Need I say more? It’s awesome.

I came across this article after working for a short time in 2014 with the author, palaeontologist Peter Douglas Ward, who’s enigmatic personality will engage you in his science as if his life depended on it. His story here is beautiful, haunting, fascinating.

Hand picked for you: The Story of Nautilus.

Follow Nautilus: WebFacebook | Twitter

 

new phil

5. New Philosopher

Another home grown magazine to be proud of. Each edition is set around a philosophical theme and features an interview with a leading intellectual – previous subjects have included the likes of Noam Chomsky, Jane Goodall, Peter Singer and David Wood.

I’ve listed the shortest article of all here: 13 questions with Michael Leunig, beginning with 1. What is the biggest threat to our minds? Answered with “Our minds.” and culminating with “What is the meaning of life?” you’ll have to start reading to find out 🙂

Hand picked for you: The Cartoon Philosopher: 13 questions with Michael Leunig

Web | Facebook | Twitter

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Acids & Bases: a Guide to Tutorial 9 (Part 2)

This is the sequel to the post Acids & Bases: a Guide to Tutorial 9 Part 1.

See below for hints and tips and things you should know for questions 9.17-9.36.

Leo acidbase

Questions 9.17, 9.18, 9.19, 9.20, 9.21
Using equilibrium expressions for pKa to calculate pH and vice versa

  • Understand how to write equations for the dissociation of acids and bases with water. The general chemical equations are as follows:General equation of dissociation of an acid, HA in water:HA + H20 → A + H3O = KaGeneral equation of dissociation of a base, B in water:
    B + H20 → BH+ + OH = Kb
  • Know how to construct the equilibrium expressions for the above dissociation equations:Image result for acid dissociation constant    Understand that the concentrations of the species that we plug into the above expressions are the equilibrium concentrations after dissociation has occurred (not initial concentrations of acid or base)
  • Know or be able to derive the following equations:pH = -log[H+] and rearrange to:
    [H+] = 10-pH


    pOH = -log[OH]
    and rearrange to:
    [OH] = 10-pOH
    [H+][OH] = 1 x 10-14 and rearrange to:
    pH + pOH = 14
  • Be able to construct an equilibrium table (sometimes known as an ICE table or RICE chart, see here for an explanation) to show how concentrations change from initial to equilibrium concentrations
  • Understand the weak acid/base approximation-if you are told that the acid or base used is weak, then it will hardly dissociate at all. The initial concentration of acid or base will be pretty much the same at equilibrium. So we can approximate and make our calculations easier.
  • Equation used to calculate the percent ionisation of an acid or base:percentionisation

Step by step guide:

1. Write out the equation for the dissociation of the acid or base with water.

2. Ascertain what variable you need to calculate based on which of the following equilibrium expressions you will use:

Image result for acid dissociation constant or 
for example, you might be given the pH and therefore can calculate the Hconcentration, or you may be given the pKa and will need to convert this to the Ka.

3. Construct an ICE table in order to work out equilibrium concentrations.

4. Plug these values into one of the equilbrium expression equations above, you may need to rearrange and/or do a weak acid approximation in order to arrive at the value you need to answer the question.

5. Calcuate percent ionization if required using the equation shown earlier.

 

Questions 9.22 and 9.24
Acid strength as a result of molecular structure

  • Carboxylic acids are organic acids and are weak acids.
  • Be familiar with the 6 common strong acids:  hydrochloric acid (HCl), hydroiodic acid (HI), hydrobromic acid (HBr), perchloric acid (HClO4), nitric acid (HNO3) and sulfuric acid (H2SO4). These acids all ionize 100% in water. Know that anything that you come across that is not one of these strong acids is most likely a weak acid.
  • Understand how molecular structure affects acid strength. A general understanding of electronegativity and periodic trends would help here.
  • Benzoic acid is an organic acid with the carboxylic acid functional group, COOH. Boron and Fluorine are in the same period, so their acids, boric acid and hydrofluoric acid can be compared on the basis of the relative electronegativities of Fluorine and Boron. Fluorine is much more electronegative than Boron, so is a much stronger acid (although both are classed as weak acids).
  • Hydrofluoric acid, HF and iodic acid, HI are hydrogen halides, and their relative strength can be illustrated by the trend of acidity within the group 17 halogens. Unlike the trend for acidity across a period, the acidity down group 17 does not follow electronegativity. Iodic acid is the stronger acid of the two based on the poor orbital overlap due to size mismatch of the two atoms meaning that the H-X bond is weaker. This trend is discussed in the lecture notes for this topic.

 

Questions 9.23 and 9.25 – 9.28 and 9.30-9.32
Buffers and the Henderson-Hasselbalch equation

  • Know what a buffer is.
  • Be able to recognise and distinguish between acids, bases and their salt forms.
  • Understand how to use the Henderson-Hasselbalch equation:


Know that sometimes A is replaced with “base” and HA is replaced with “acid”
Keep in mind that when equal concentrations of acid and base are used, that it results in the entire last variable in the equation being “log 1” which is = 0.

Questions 9.29 and 9.33 – 9.36
Acid Base Titrations

  • Know the terms: equivalence point, half equivalence point, end point and be able to label them on a titration curve.
  • Know how to construct a titration curve (plot mL vs pH) and know roughly the different shapes depending on whether the titration involves a strong acid/strong base, strong acid/weak base or weak acid/strong base

 

Extra resources:

Check out the videos below from Crash Course and Khan Academy that summarise the concepts required for this tutorial.


Titration curves and acid-base indicators:

 

For more information about how the cbsquared Chemistry for GAMSAT course can help you achieve your GAMSAT and medical school goals, or just for some guidance and advice about how to kick start your study, please feel free to get in touch.

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The GAMSAT “test run”. Will you end up another crash test dummy?

The GAMSAT test run. Otherwise known as the “trial run”, “first attempt”, “going to see how I go”.

It can be a very beneficial experience, hey, it might be enough to get you a place into med school! But you can easily end up as just another GAMSAT crash test dummy.

Rather than squandering a lot of money and wasting an entire day, here’s how to best use your “GAMSAT test run” opportunity.

 

Are you the next crash test dummy?
Are you the next crash test dummy?

 

If you’ve never sat GAMSAT before, there are a lot of unknowns.

Is the test harder than the practice books?

How will I deal with the pressure?

Do I have the stamina to last the whole day?

Will I have enough time?

What strategy will I take when answering the questions?

And the big one:

How will my result compare to the rest of the cohort?

Some of these questions can only be answered in one way-by sitting the GAMSAT. However there are some aspects that can be worked through before you enter the testing centre.

Here I discuss the benefits of the “GAMSAT test run” and 5 ways to get the most out of it.

 

Is the test harder than the practice books?

  • Depends on how prepared you are. Be prepared to be faced with questions that are outside of the concepts that appear in the practice books. You should have a good idea of what concepts are testable across all subject areas.
  • Ratio of Biology/Chemistry/Physics: Often students will say to me “there was so much organic chemistry!”. This is more a reflection of the student perhaps not feeling as confident with organic chemistry and so spending more time on those questions and then feeling like the test was full of them. The ratio of Biology/Chemistry/Physics doesn’t change much from test to test and the ratio of general chemistry to organic chemistry remains pretty much constant too.
  • If you come out feeling like there was a lot of one particular area, or that you struggled with, or took more time on particular questions, make a note of this to add to your study plan for round two.

How will I deal with the pressure?

  • Do a practice test (or two) under test conditions in the weeks leading up to the exam. This is possibly the one of the best preparation tools you have.
  • Remind yourself that it’s not the end of the world if don’t get the marks you want this time. The test is stressful enough as it is, putting extra pressure on yourself is just counterproductive and can actually make you perform worse.
  • Don’t let other test candidates put you off your game! Get into a good headspace going into the test and don’t let others nerves or overt confidence interfere.
  • If you feel you didn’t go as well as you would have liked in the first section, don’t let that taint the rest of your day. Put it behind you and move into Section III with confidence.
  • Use visualisation techniques in the weeks and months leading up the exam to help you maintain confidence, positivity and a clear head on the day.

Do I have the stamina to last the whole day?

  • Again, taking a practice test or two under test conditions leading up to the day is invaluable. Use it to work on your focus and concentration limits.
  • Eat food that is low GI and will keep your energy levels stable throughout the day. You aren’t allowed to eat food during the test, so make sure you eat well on the day prior and have a decent breakfast and packed lunch. The brain is an energy hungry organ, so the last thing you want is to start feeling light headed because you’ve hit a sugar low midway through section III.
  • Be prepared for the unknown. Wear layers-as testing centres might be colder or hotter than the environment you’re used to working in. Or you might warmer on the day because of your nerves!

Will I have enough time?

  • Be aware that the GAMSAT is designed to be HARD. It is designed to separate out the cohort as much as possible. This means that even if you only have time to answer two thirds of the questions,  you could still end up with a pretty competitive result.
  • At the end of the test, take note of how many questions you answered with confidence, how many were educated guesses, and how many you simply bubbled in because you ran out of time. This information along with your results can help you to formulate a strategy if you have to sit a second time around.

What strategy will I take when answering the questions?

  • What will you do in the reading time-start answering the first question, look at what questions are there, or start reading through a particularily long stimulus?
  • Will you answer all the questions in the order they appear, or will you answer all the chemistry questions first?
  • Whatever you do, you need to have a clear plan in place about what you will as soon as the exam commences. This will help calm your nerves, give you focus and ultimately save you time because you wont be floundering trying to decide what to do on the day.

And the question everyone wants to know:

How will my result compare to the rest of the cohort?

  • If you don’t get the marks you want first go, your result is really the best indicator of how much work you have to do.
  • You may be surprised at how well you did in sections I and II, but shocked at your Section III (science) mark.
  • Most students seem to underestimate the amount of preparation required to do well in section III.
  • Section III is weighted double, so a good score can really bump up your overall GAMSAT result.

Use your mark from your first go as tool for devising a plan for future attempts. You can draw motivation from your score and focus on areas that you know you need to improve on.

You can also be pragmatic, work out what sort of preparation or extra help you might need. Whether that’s a designated science course, a GAMSAT study plan, or just a kick up the bum to get you a bit more focussed and determined with your study efforts.

If you’re after some advice based on your specific background, please don’t hesitate to get in touch, or join our mailing list, or drop us a line using the red “contact us” pop up at the bottom right of this page.

Good luck!

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Handy reference: List of ions, orbitals, equations & constants

When you’re getting started with Chemistry, the volume of information thrown at you can seem overwhelming.

Students taking the cbsquared Chemistry for GAMSAT course have a host of resource documents available to them in the course already, but I thought I would post a few extra online resources with a few great images to help you form a visual picture of the building blocks of chemistry at the molecular level.

Please note: here is no need to rote learn any of this material for the GAMSAT!

1. Table of common polyatomic ions with 3D models.

Once you get to topic 2 and 3, we start talking about lewis dot structures and it can be helpful to be familiar with some common polyatomic ions.

Polyatomic ions table

 

 

2. Orbitron, a website with images showing what the orbitals and hybridised orbitals look like in 3D

Useful for understanding what an atomic orbital might look like, and also for the hybridisation topic, to get an idea of what hybrid orbitals look like.

Orbitron

 

 

3. Lists of useful equations and physical constants used in physical chemistry.*

*PLEASE NOTE: You do not need to rote learn these equations or physical constants. They will be provided in the stimulus of the GAMSAT question. You should learn the very basic equations, such as c = n/v and n = m/M for chemistry questions.

For more information about how the cbsquared Chemistry for GAMSAT course can help you achieve your GAMSAT and medical school goals, or just for some guidance and advice about how to kick start your study, please feel free to get in touch.

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Making maths in physical chemistry less scary

Once students arrive at the physical chemistry topics of the Chemistry for GAMSAT course, they are confronted with a subset of mathematical skills that are required.

The maths is quite straight forward believe it or not, but the big equations and the use of logarithms can make these questions seem more difficult, and let’s face it, sometimes kinda scary!

Fear not, it takes a little practice but the more you see and use your basic math skills with these equations, the less scary they become, until you’re laughing in the face of huge equations!

The following set of videos cover the following mathematical techniques:

  • Rearranging equations involving logs
  • Using simultaneous equations to find values for more than one unknown
  • “Linearising” an equation (ready for graphing, or just to simplify)

The idea of this post is to remove some of the “scary factor” when you see complex equations, and to help you become more familiar with, and learn how to manipulate them.

All the videos are around 3 minutes long. If you don’t understand the rearragements or log rules, you should consult the other maths for Chemistry resources on this blog, such as “Logs in less than 5 minutes“.

Resource 1: Logarithms in Chemical calculations

The following resource explains the maths used when manipulating some common physical chemistry equations.

  • Nernst Equation: The use of log to base 10 and the natural log (ln) in the Nernst equation is shown, and how the equation can be rearranged to be able to plot on a straight line graph.
  • Gibbs Free energy related to the Equilibrium Constant: How to rearrange the equation ΔG = RTlnK to solve for using log rules
  • Clausius-Clapeyron Equation (relating vapour pressure to temperature): Another example of how to rearrange an equation involving log rules.

Resource 2: Simultaneous Equations and the Arrhenius Equation

This video is concerned with the Arrhenius equation (relates the rate constant k to the temperature). It summarises the following:

  • Rearranging the Arrhenius equation into a “linear” form
  • Using simultaneous equations to solve for more than one unknown

Resource 3: Simultaneous Equations and Thermodynamic Expressions

More practice at using simultaneous equations and rearranging equations with logs in them.

I hope these resources help you feel more at ease with some scary looking equations.

For more information about cbsquared GAMSAT preparation courses, please visit: https://cbsquared.co/learn/courses/

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Back to basics: Graphing and the GAMSAT

This week, in the Chemistry for GAMSAT course, we start on the GASES topic. For many, this topic also marks their first foray into maths and graphing as part of their GAMSAT preparation.

The GAMSAT is notorious for using graphs to represent data, and for requiring that graphs are interpreted correctly to answer a question.

But hands up who can’t even remember doing a simple straight line y = mx + c graph since school, and who’s graphical prowess is either limited to a graphics calculator, or those blue pie charts in excel?

Never fear.

Being able to interpret and draw a graph are excellent skills to have, they can be applied across all three of the sciences of GAMSAT Section III, and they are suprisingly easy to learn!

Here are a couple of resources for getting up to speed with graphs.

Resource 1: BBC Bitesize – Graphs and Proportion

This resource gives a quick rundown of:

  • direct proportion
  • inverse proportion
  • straight line graph (proportional)
  • quadratic
  • cubic
  • square root
  • inverse proportion
Credit: bbc.co.uk (click to link to original article)
Credit: bbc.co.uk (click image to link to original article)

 

Resource 2: Zona Land Education – A closer look at graphing

Weird name, and old school looking website, but good explanations. Scroll to the bottom for links to each of the following:

  • Direct proportions
  • Linear functions
  • Inverse proportions
  • Inverse proportion graph
  • Rational functions, 1/x
Image Credit: Zona Land Education (click to link to original article)
Image Credit: Zona Land Education (click to link to original article)

 

I hope these resources helped jog your memory and enable you to “tow the line” so to speak, when it comes to graphical analysis.

For more information about cbsquared GAMSAT preparation courses, please visit: https://cbsquared.co/learn/courses/

 

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i.o.u. an explanation for a.m.u.

Ok, let’s get something straight.

There’s a lot of language to get your head around when you first start out with Chemistry, and it all starts with how the very smallest chemical particle is measured.

In topic 1 of the Chemistry for GAMSAT course, we start from the very basics, so this post is to help you get off to a good start.

It’s the small things….

We are dealing with such small particles, that have very very small masses, so there are some unique terms that have been derived to help us. It will help if you have an understanding of the following terms:

  • atomic mass
  • relative atomic mass (replaces the old term atomic weight)
  • unified atomic mass unit (replaces the old term atomic mass unit)

The following video has a good introduction from first principles, including a quick explanation of the distinction that physicists make between weight and mass. The chemistry definitions start around the three minute mark.

 

Notice that the video makes no mention of relative atomic mass, or of unified atomic mass unit, which are actually the new terms for the atomic weight and the atomic mass unit respectively.

Although still somewhat shrouded in controversy among chemists, the terms relative atomic mass and unified atomic mass unit (still abbreviated to amu) replace the old terms. However, both terms in each case are still in use and are officially sanctioned by the International Union of Pure and Applied Chemistry (IUPAC)

Out with the old, in with the new:

  • The relative atomic mass is exactly equivalent to the old term atomic weight. Changed in 1961 after controversey arising from the distinction between weight and mass.
  • The unified atomic mass unit is the new term for atomic mass unit, both are abbrevieated to amu.

What does it all mean?

unified atomic mass unit

  • Defined 112 of the mass of an atom of carbon-12.
  • Symbol u.
  • One unified atomic mass unit is approximately the mass of one proton (or one neutron) and is equivalent to 1 g/mol.
  • Has a value of 1.660538921(73)×10−27 kg.

relative atomic mass 

  • Defined as m/mu where m is the average mass of an element and mu is atomic mass constant. (mu = m(12C)/12 which = 1 Da or 1 u).
  • Symbol Ar.
  • This is the number that appears on the periodic table which takes into account natural isotopic abundances.
  • Indicates a ratio-it compares a property of one substance to the same property of another substance. Hence it has no units, it is strictly not a mass but a ratio of two masses.
  • However, for both practical and historical reasons, relative atomic masses (and molecular masses) are almost always quoted in grams per mole (g/mol or g mol−1) in chemistry.

atomic mass

  • Defined as the mass of an atomic particle, sub-atomic particle, or molecule.
  • Symbol ma
  • Commonly expressed in unified atomic mass units (u)
  • Does not take into account natural isotopic abundances.

For another explanation of the atomic mass units, relative atomic mass and natural isotopic abundance, check out the Fuse School videos below:

This is covered in Tutorial 1 of the Chemistry for GAMSAT course. To view a preview of the course click here.

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Understanding how molecules bond in 3D – Hybridisation

Hybridisation is useful to understand for the GAMSAT at face value, and also to gain a deeper understanding of more difficult organic chemsitry concepts. For GAMSAT, focus on sp, sp2 and sp3 hybridisation.

You can understand hybridisation the quick way or the more in depth way.

The quick way is mostly about simply matching the hybridisation labels sp, sp2 and sp3 with the “regions of electron density”.  Remember that sp hybrid orbitals are made of two atomic orbitals: an s and a p, sp2 hybrid orbitals are made with one s and two p atomic orbitals and sp3 hybrid orbitals are made of one s and three p hybrid orbitals.

This is explained by Ben in this short video:

You can also understand hybridisation using orbital box diagrams, and 3D representations of the atomic and molecular orbitals. When you do this, you can get a real visual picture of how the electron density is redispersed from a single atom, to around two or more atoms when they bond with one another.

The following video contains a three dimensional video of the formation of hybrid orbitals.

The hybridisation models past the 8 minute mark are outside of the scope required for understanding of GAMSAT concepts, but are interesting to see how the hybridisation theory can be expanded to bigger molecules.

 

If you’re struggling…

The Khan Academy always has great videos that really break down the concepts, although they often take a bit longer to watch.

Sal Khan breaks down his explanation into two videos, one focussing on sp3 hybridisation and sigma bonding, and the other on sp and sp2 hybridisation and pi bonding.

 

 

Hank Green from Crash Course always has colourful and unique ways of explaining things, so this video is also worth a watch if you’re still a little perplexed-or would like some light entertainment that involves learning about hybridisation…yes it’s possible 🙂

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