STPM 化学部落各和練習下載+2009 chemistry 重要 topic

891108

不明白以下CONSEP

MELTING POINT AND BIOLING POINT OF
SIO2
AL2O3
WHICH HIGHER?
MY CONSEP IS  SIO2  GIANT COVALENT STRUCTURE
AL2O03 IS HYFROGEN BOND BETWEEN AL AND H MOLECUL
SO WHICH ONE STRONG AND BP MP  IS DEPEND STRUCTURE OR BOND??

玄風劍

原帖由 891108 于 26-10-2008 01:42 AM 发表
不明白以下CONSEP

MELTING POINT AND BIOLING POINT OF
SIO2
AL2O3
WHICH HIGHER?
MY CONSEP IS  SIO2  GIANT COVALENT STRUCTURE
AL2O03 IS HYFROGEN BOND BETWEEN AL AND H MOLECUL
SO WHICH ONE STRONG  ...

where did you get H from Al2 O3 ?
there is no hydrogen boond exist in that particle.....
if we compared hydrogen bond with a infinite tetrahedral structure..... the infinite tretrahedral strucutre has the higher mp and Bp

玄風劍

原帖由 ckkwill 于 24-10-2008 12:48 PM 发表
很多的中學生有一個缺點，就是把參考書儅聖經。其實stpm的參考書一點幫助也沒有。它最多只是告訴你哪一些是在syllibus裏要讀的東西。真真想弄懂弄明白的話，去圖書館找college text看，就會一清二楚了。一本弄不懂看 ...

這句話我很喜歡....很有根據性

891108

原帖由 玄風劍 于 26-10-2008 02:29 PM 发表


where did you get H from Al2 O3 ?
there is no hydrogen boond exist in that particle.....
if we compared hydrogen bond with a infinite tetrahedral structure..... the infinite tretrahedral strucut ...

sorry
im wrong
that is no H bond in  AL2O3
but may i ask
AL with form  H bond with what  molecul?
i remember got 1
izit OH??

玄風劍

Al form no H bond with any other compound. It is because Al is not a requirement  to form a H bond.
back to definition , H bond is form when a H compound is bonded with these compound  F, O,N.
so for Al(OH)3
it is still ionic bond form between Al and OH....
but as i know , H bond is only for the inorganic compound (correct me if i am wrong)
for example R-OH compound, whereby R is a long chain of hydrocarbon.
the h bond exist is between the R-OH and the R-OH molecules
and the H bond position is linked between the OH to another OH

      R- O-H
            ll
            H-O-R             ll = hydrogen bond

ynnee

为什么你spot 的题目没有organic的？

玄風劍

如果他全部都spoT 了 ....那麼步就是要讀完全部?
其實在該考卷的時候,會看到2種人
A)ORGANIC 系的人  B) PHYSICAL CHEMISTRY 的人
就算你不會oRGANIC 我覺得你還可以SCORE 的

ckkwill

謝謝nikuang幫我回答了。
mp and bp depends on both bonding and structure
SiO2 = covalent bond with giant molecular structure :highest mp bp
Al2O3 = ionic with covalent character, so in between giant ionic and giant molecular structure, so lower mp then SiO2

891108

原帖由 ckkwill 于 27-10-2008 04:03 PM 发表
謝謝nikuang幫我回答了。
mp and bp depends on both bonding and structure
SiO2 = covalent bond with giant molecular structure :highest mp bp
Al2O3 = ionic with covalent character, so in between giant ...

我也觉得是这样
但是Chemistry Pahang Trial STPM 2008 [edu.joshuatly.com].pdf
却调反

891108

原帖由 玄風劍 于 27-10-2008 01:14 PM 发表
如果他全部都spoT 了 ....那麼步就是要讀完全部?
其實在該考卷的時候,會看到2種人
A)ORGANIC 系的人  B) PHYSICAL CHEMISTRY 的人
就算你不會oRGANIC 我覺得你還可以SCORE 的

但是要make sure physical是很厉害那种。。

ynnee

这就是我最担心的，如果physical不会做就死翘翘了！

ckkwill

說了很多次了，trial exam 的題目不用去看他。10題會有5題是錯的。
每一題正常的題目都給改到亂七八糟，信一半也死。如果打傢還是堅持做tial的題目的話，大家好自為自。

ckkwill

physical 以時間來講很難可以把全部東西都弄懂。除非stpm有5年的時間。所以，如果想拿好成績的話, 不如多花點時間在organic 和inorgainic. 如果成績不重要的話，那只做physical 也無妨。

ynnee

我比较会physical 嘛！organic做三题至少错两题！您的网站真的很hot哦！进了半个小时都进不去！

玄風劍

Physical chemistry required more skills of answering ....( pls refer to your teacher and your tuitor) not necessary u can score if u just understood the concepts
emphasizing the technique of answering !!!!
organic has the lower marking skeme .... so even u have a little understanding about i

ynnee

so ,organic difficult mah?bcoz my teacher teach too fast,还我整天在发梦！

891108

原帖由 ckkwill 于 27-10-2008 06:58 PM 发表
說了很多次了，trial exam 的題目不用去看他。10題會有5題是錯的。
每一題正常的題目都給改到亂七八糟，信一半也死。如果打傢還是堅持做tial的題目的話，大家好自為自。

那应该做什么呢

ckkwill

只剩下2星期，要做也不能做了。只有多做一點題目，明白問題的重點，看marking skeme 的解答方式，那一些是point, 那一些是垃圾。別亂寫一通。有哪一些地方覺得忘了或不清楚的，重新再看一遍。別大概懂。這樣只有等死。要真真的懂。不要懶惰思考。
好像旋風劍說的一樣，physical明白是沒用的。一句裏面每個字你都懂不代表你真正明白他的意識。有一些concept 我用了5年才搞清楚。
eg past year question:
Why use volume to calculate Mr the value is smaller than use n = m/Mr to find?
單單要明白那一個是theory 那一個是experimental 我也要用了超過5個小時。

morphv02c01

一个忠告，organic不能放，放掉肯定你拿不到A，不管你的physical多么厉害。。

玄風劍

organic isnt easy nor hard also..... as i said you will found out those reaction sometimes linked to each other.... (inconclusion u dont have to be stress out with that many reactions need to memories)
in answering organics... first we must identified types of question
thr are 7 types of question may ask in the exams : schematic, reaction ,short essay , long essay, etc.....
(sadly i cant remember those , as there are long throw into the back of my brain   )
each of it required diff types of answering , of course u need to have some answers (e.g. reaction equation, catalyst, temp, observation.....) to gain the marks.
after knowing this... u must or atleast able to write down all the reaction involve about organic reaction (which in the syllabus) trust me ... after going through this barrier .. i bet u can easily see through the trick of the any organic question that try to bombared you at the exams.

good luck