gas to solid (sublimation @ desublimation)????

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[Lim Tze Khai]

Any one can confirm the term for process involving change of state from gas to solid?

In text book, sublimation process but in CD, desublimation/deposition process!!!!

For me, it should be desublimation or deposition. Any comment?

This is bcoz higher level book use this term.

[Lim Tze Khai]

Any teacher can answer this question?

[Choo Yih Teen]

http://en.wikipedia.org/wiki/Desublimation

solid to gas - sublimation
gas to solid - desublimation / deposition

maybe the translator do direct translation, since in BM last time, both changes from gas to solid and solid to gas are named as "pemejalwapan". not sure with the spelling anymore..   

hope this helps

[Ch'ng Oon Hock]

http://en.wikipedia.org/wiki/Desublimation

solid to gas - sublimation
gas to solid - desublimation / deposition

You are right about this.
Actually I have checked and tried to answer to Lim, but I was unable to access to engkabang.net for the reply.

Anyway, thanks for confirming what I've read.

[Ting Tin Chung]

http://en.wikipedia.org/wiki/Desublimation

solid to gas - sublimation
gas to solid - desublimation / deposition

Hi,
According to the Form 4 text book, they are using the term sublimation for both condition. If we introduce the term to the student (desublimation / deposition), i mean Form 4 and Form 5 students, and they use it in the SPM exam.... will the examiner accept the answer? Here is the problem!! What the students learn at Form 4 and Form 5 different with Form 6......

[Lim Tze Khai]

In text book, sublimation process but in CD, desublimation/deposition process!!!!

The CD that i mean is the Form 4 CD.

[Lim Tze Khai]

Actually I have checked and tried to answer to Lim, but I was unable to access to engkabang.net for the reply.

Thanks for your time to check the term.

Hope that we can work together to improve the knowledge of chemistry for teachers, students and ourselve.

[Jong Kah Yin]

Just let me offer my 2 cents' opinion here. Both are terms used is correct. But for the interest of students, just use sublimation as in the text book. Normally, should there be a discrepancy in the terms used, they usually refer to textbooks and syllabus. Sometimes too many terms used will confused students and they maybe penalised in SPM exams.

[Lim Tze Khai]

Just let me offer my 2 cents' opinion here. 

Thank you for sharing your opinion.

[Lim Tze Khai]

Example of chemical undergo sublimation!!!!

   Given in text book,

      Iodine, carbon dioxide and ammonium chloride 

What do you think?? Is the given example correct.....

Let discuss ... will give my opinion later....

[Jong Kah Yin]

Personally, i think there is nothing wrong.  Please correct me if I m wrong.
Ammonium chloride, appear to sublime because of chemical reactions. When heated, ammonium chloride decomposes into hydrogen chloride and ammonia in a reversible reaction:   
NH4Cl → HCl + NH3

[Lim Tze Khai]

But if we study the defination of sublimation - change of physical state from solid to gas.

This mean that chemical change from solid to gas without chemical change. Right?

Therefore for me, CO₂ and I₂ undergo sublimation by changing for solid to gas without chemically changes.

But ammonium chloride which change to gas due to chemical change does not undergo sublimation.

Anyone can comment on this..... 

[Choo Yih Teen]

But ammonium chloride which change to gas due to chemical change does not undergo sublimation.

agree... if it is a chemical reaction, it is not exactly sublimation... (only appears to be... )

ammonium chloride, sublimes at 338 °C (refer to  http://www.detailsnetwork.com/en/wiki/Ammonium_chloride.html).

[Lim Tze Khai]

ammonium chloride, sublimes at 338 °C

if we study further in form 6, any compound can sublime if suitable conditions applied

for me, since text book has ammonium chloride, then, can be used too.. 

Thank you for your information.
I also have the same opinion, because most of the time "the expert" will say refer to textbook.

ammonium chloride, sublimes at 338 °C at specific pressure? but at 1 atm, it decompose to ammonia and hydrogen chloride as we know.

[Choo Yih Teen]

yupe...

that's why they say ammonium chloride appears to be sublime, as we observe, the solid really turns to gas in the experiment.

[Jong Kah Yin]

Ammonium Chloride
 
Ammonium chloride is a compound of ammonia containing the chloride radical Cl2. Ammonium chloride, when heated, undergoes thermal dissociation, to form ammonia and hydrogen chloride. Ammonia and hydrogen chloride recombine at the cooler upper parts of the test tube, and settle down as a white layer. Since the same ammonium chloride is re-obtained, this change is sometimes referred to as "sublimation". In actual sublimation, there is only a change of state and no decomposition. In the case of ammonium chloride, decomposition does take place, though the products, when cooled, recombine to from ammonium chloride.
 
 
http://www.tutorvista.com/content/chemistry/chemistry-i/physical-chemical-changes/heat-on-substances.php

This is a platform to share and exchange ideas and opinions. Please try not to be sarcastic or exude some insinuations in one form or another. The very action will discourage others to share and to join our forum. As a teacher, we should be humble and sincere to learn, showing exemplary example to students. Thank you

[Lim Tze Khai]

Thank you for the info.

question ask meant to be answer so that we can gain more knowledge.

As for this question, i think many teacher will benefit from our discussion with fact. As for me, i learn from your answer and others.

Keep on asking question and every one that part actively in the discussion!!!!!

All of us will gain benefits from it.

TQ

 

[Choo Yih Teen]

agree.. a platform for us to exchange our opinions..

[Edward Lim]

Wow, this a great place to share. I learned a lot here.
 Thank you.

I have one question. Does naphthalene melts or sublimes or both?
If it is left at room temperatue, it will sublime but if heated in water bath it will melts. Different temperature but same air pressure will make the process change. What is the triple point for naphthalene??

Hope someone can give comment. Thank you.

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