New Topic Every Week

[Harry_-]

Hi,

I am a student in high school, wanting to study Chemistry at university. I am doing a challenge to read into a new chemical topic every week. I have here an Atkins Physical Chemistry textbook and would love it for whoever is reading to give me a random number between 10 and 850, this will be a page number and I will research that topic for that week. This forum will be an account of my progress and a place to get help on the topic.

Thanks

[studiot]

Hi, Harry.

Atkins offers no concessions to those who are not studying Applied Maths and/or Physics.

Are you also taking either/both of these?

He has written some excellent books and rather cornered the (UK at least) market in textbooks at this level.

But you need to say which edition you are working from because there are many and each is laid out differently.

For instance I hav ethe 5th and 6th editions,

Page 850 starts a chapter on "Processes at Solid Surfaces" (5th)

#Whilst page 850 in the 6th is towards the end of a chapter on transport phenoma in general and the diffusion equation in particular.

I would also not recommend jumping in at random points because at any point he assumes the underlying Physics and Mathematics.

I suggest it would be better to ask folks to pick some subject heading out so that you can follow them in some sort of logical order.

[Sensei]

2 hours ago, studiot said:

I would also not recommend jumping in at random points because at any point he assumes the underlying Physics and Mathematics.

I suggest it would be better to ask folks to pick some subject heading out so that you can follow them in some sort of logical order.

Knowledge presented in later chapters usually requires that reader is already familiar with earlier chapters..

[Harry_-]

These are all good points. I have maths and physics A-level. Ok so random number won't work, has anyone got a topic which will be enjoyable? I have the 11th edition.

[studiot]

1 hour ago, Harry_- said:

These are all good points. I have maths and physics A-level. Ok so random number won't work, has anyone got a topic which will be enjoyable? I have the 11th edition.

OK I will see what I can come up with in the way of a list, but it will have to be to topic headings, rather than page numbers I do not have access to the 11th ed.

In the meantime here are a couple of linked challenges for you to investigate and think about.

1) Chemistry recognises more states of matter than Physics, which recognises only 4 (solid, liquid gas ans plasma). Can you think of any?

2) A large part of Physical Chemistry is about the combined action of large collections of particles which obey many common equations, for example the bulk of free electrons in a semiconductor have been called an 'electron gas' because they obey similar laws to the gas laws. So the 'particles' are not always molecules or even atoms.
Can you identify any more? Hint some are called colligative properties.

[Harry_-]

On 9/22/2019 at 5:37 PM, studiot said:

1) Chemistry recognises more states of matter than Physics, which recognises only 4 (solid, liquid gas ans plasma). Can you think of any?

Ok so this question took me longer than expected but I think I have an answer. I looked into the phase diagrams of water and found that at high pressures/ low temperatures , the liquid and gas state merge into something in between. I looked into it just a little and its called a super critical fluid, that's as far as I have got.

On 9/22/2019 at 5:37 PM, studiot said:

2) A large part of Physical Chemistry is about the combined action of large collections of particles which obey many common equations, for example the bulk of free electrons in a semiconductor have been called an 'electron gas' because they obey similar laws to the gas laws. So the 'particles' are not always molecules or even atoms.
Can you identify any more? Hint some are called colligative properties.

As for this question, I have just read 'A brief introduction to superconductivity' in which it explains that superconductivity is a quantum phenomena. I'll be honest, a lot of the quantum mechanics were too complicated for me however I learnt that in this superconducting state electrons work as pairs to flow through a superconductor. Is this an example of particles not acting as molecules/ atoms?

[studiot]

Here are a few states recognised by Chemists.

The crystalline state
The gaseous state
The metallic state
The amorphous state (charcoal, elastic, rubber etc)
The vitreous state (glass, supercooled boron trioxide)
The liquid state
The dissolved state
The disperse state (colloids)
The ionic state
The interfacial state
 

I'm glad you found phase diagrams because that was on my list of 12 little pieces ( not yet finished but here are some more)

(3) Binary mixtures , phase diagrams, eutectics, the phase rule.

(4) pH, pOH and p(X)

(5) Chemical applications of polarised light.

(6) The Boltzman distribution

(7) Metallic bonding and Fermi levels

(8) Electronegativity v electron affinity

[Harry_-]

17 minutes ago, studiot said:

Here are a few states recognised by Chemists.

The crystalline state
The gaseous state
The metallic state
The amorphous state (charcoal, elastic, rubber etc)
The vitreous state (glass, supercooled boron trioxide)
The liquid state
The dissolved state
The disperse state (colloids)
The ionic state
The interfacial state
 

I'm glad you found phase diagrams because that was on my list of 12 little pieces ( not yet finished but here are some more)

(3) Binary mixtures , phase diagrams, eutectics, the phase rule.

(4) pH, pOH and p(X)

(5) Chemical applications of polarised light.

(6) The Boltzman distribution

(7) Metallic bonding and Fermi levels

(8) Electronegativity v electron affinity

Thanks so much for your continued help, I will look into all of these in the coming weeks. Your questions are also very helpful, I have upcoming interviews where they will be asking me questions similar to as you have just posed. I don't think my answer to Q2 was quite satisfactory and this is mainly as I don't think I understand the question, could you clarify the question further?

[studiot]

23 hours ago, Harry_- said:

Thanks so much for your continued help, I will look into all of these in the coming weeks. Your questions are also very helpful, I have upcoming interviews where they will be asking me questions similar to as you have just posed. I don't think my answer to Q2 was quite satisfactory and this is mainly as I don't think I understand the question, could you clarify the question further?

You also mentioned complicated quantum mechanics.

Learning your first QM fromAtkins is pretty daunting.

So I have a suggestion.

Sometimes a gentler introduction aimed at another discipline can be very helkpful, especially in the initial stages.

This current Phys Chem book from Oxford can be obtained very cheaply  second hand from Amazon, Abe or Ebay, and serves this purpose admirably.
I have included a couple of pages from the quantums ection, which is the easiest simple explanation I have seen.

 

 

The book is also similarly clear in other chapters.

 

As regards my number (2)

23 hours ago, Harry_- said:

I don't think my answer to Q2 was quite satisfactory and this is mainly as I don't think I understand the question, could you clarify the question further?

No I was meaning things like vapour pressure, osmosis, Raoult's law, depression of freezing point, elevation of boiling point......
Many of these properties have a common basis in that they depend upon the number of particles.

But this will become clearer when I add the last few topics (much of which can be found in Price et al.

[studiot]

I have carefully avoided the topics needing more difficult maths. Also quantum theory as it affects Chemistry needs to be worked through a bit more.
But it is important to realise that whilst Physicists deal largely with atimic theory, this is of little use to Chemists, who deal largely with molecules.
And molecules have structure and bonding to consider. Further some of the states of matter (eg metals and ionic crystals) amount to giant 'molecules' the size of the substance.

Following on from topic (1) we have topic (9)

(9) What types of bonding can you identify?

Chemists are also interested in reactions so let us do a bit of chemical maths

(10) Investigate the reaction, the  equilibrium constant, the solubility constant, the dissociation constant and the law of mass action and the mathematics of chemical reactions.

Here is an example you should be able to follow but ask if need be.

 

Hydrogen Flouride partially dissolves in water as hydrogen ions and flouride ions.
If the equilibrium constant is 6.7 x 10^-4 calculate the concentration of the species that form when 1 mole of HF is dissolved in water to give 1 litre of solution.

So firstly we write down the (dissociation) reaction.

HF = H⁺(aq) + F^- (aq)

From this we can see there are three unknowns since the dissociation is not complete (HF is a weak acid)

The unknowns are:- The concentrations of the hydrogen ions, the flouride ions and the remaining hydrogen flouride molecules.

Are you familiar with the notation of putting the species inside a square bracket to denote concentration?

Thus the concs are [H⁺], [F^-] and [HF].

Three unknowns so mathematics tells us we need three equations.

1) From the definition of the equilibrium constant

[math]\frac{{\left[ {{H^ + }} \right]\left[ {{F^ - }} \right]}}{{\left[ {HF} \right]}} = {K_a} = 6.7x{10^{ - 4}}[/math]

2) Electroneutrality or charge balance.

The solution starts off electricall neutral so the number / concentration of negative charges must equal the number of positive

[math]\left[ {{H^ + }} \right] = \left[ {{F^ - }} \right][/math]

3) Mass balance.

The total number of moles of flourine must be the same as we started with and we are told that we started with 1 mole of HF ie 1 mole of flourine.

[math]\left[ {HF} \right] + \left[ {{F^ - }} \right] = 1[/math]

Using those three equations you should be able to come to the conclusion that

[H⁺] = [F^-] = 0.0256M and [HF] = 0.97 M

 

 

 

[Dagl1]

On 9/24/2019 at 12:00 AM, studiot said:

Here are a few states recognised by Chemists.

The crystalline state
The gaseous state
The metallic state
The amorphous state (charcoal, elastic, rubber etc)
The vitreous state (glass, supercooled boron trioxide)
The liquid state
The dissolved state
The disperse state (colloids)
The ionic state
The interfacial state
 

I'm glad you found phase diagrams because that was on my list of 12 little pieces ( not yet finished but here are some more)

(3) Binary mixtures , phase diagrams, eutectics, the phase rule.

(4) pH, pOH and p(X)

(5) Chemical applications of polarised light.

(6) The Boltzman distribution

(7) Metallic bonding and Fermi levels

(8) Electronegativity v electron affinity

Most of the content in this thread goes over my head (for now), but I am wondering, is his answer regarding super critical fluids not considered a distinct state (I did not see it in your list (looked up SCF but did not spot any different name presented on the wikipedia that corresponds with your given states). Apologies if I missed it!

Thanks!

-Dagl1

[studiot]

1 hour ago, Dagl1 said:

Most of the content in this thread goes over my head (for now), but I am wondering, is his answer regarding super critical fluids not considered a distinct state (I did not see it in your list (looked up SCF but did not spot any different name presented on the wikipedia that corresponds with your given states). Apologies if I missed it!

Thanks!

-Dagl1

There is no hard and fast rule about what can be called a 'state' Supercritical could be so considered since it is a condition where there is no distinction between liquid and gas.

Moore (Physical Chemistry) calls this a fluid. FYI the meniscus is the boundary between liqid and gas when there is a distinction.

Note that 'super' in this context means above - it is the temperature that is above the critical temperature. It does not mean 'extra special'.

[Dagl1]

17 minutes ago, studiot said:

There is no hard and fast rule about what can be called a 'state' Supercritical could be so considered since it is a condition where there is no distinction between liquid and gas.

Moore (Physical Chemistry) calls this a fluid. FYI the meniscus is the boundary between liqid and gas when there is a distinction.

Note that 'super' in this context means above - it is the temperature that is above the critical temperature. It does not mean 'extra special'.

[Picture]

Thanks! I will read it again and let the information sink in (I feel it's not intuitive that density of a vapor increases when temperature increases, but I suppose that is the result of the Ideal gas law, just conceptually I don't get it; if volume remains the same, why would the mass/volume increase if I heat something, kinetic energy doesn't contribute to mass right?) 
Please excuse my general ignorance on this topic, I've only recently become interested in these things and should have paid a lot more attention in high school;p.

___________________________________________________________________________________

Another question, related, but which possibly should become a different thread (I'll let the mods judge that), could you explain why water's density is highest at 4 degrees in a, conceptually understandable manner? (I've read: https://www.quora.com/Why-is-water-more-dense-at-4°C-than-at-0°C?redirected_qid=12443275#!n=12 but I find it difficult to follow + I would like to understand why the maximum of the density temperature graph is 4 degrees, what fundamental properties are behind (why is it not 5 degrees etc.), from the explanation on that website, if I leave 4 degree water for long enough without introducing new kinetic energy in a room that is exactly 4 degrees, it should eventually become ice... ?) 

edit: reason for my last comment regarding ice formation [From the website: "At 4 °C, the clusters start forming.The molecules are still slowing down and coming closer together, but the formation of clusters makes the molecules be further apart.Cluster formation is the bigger effect, so the density starts to decrease.Thus,the density of water is a maximum at 4 °C."]

-Dagl

Edited September 26, 2019 by Dagl1