O-Level Chemistry

PSLE marks the graduation of Primary school students and their entry into Secondary schools as teenagers. Discuss all issues about Secondary schooling here.
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questionable_i
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Re: O-Level Chemistry

Post by questionable_i » Sun Jul 24, 2016 5:29 pm

Jaszon99 wrote:Hi can anyone help me with chemical equation symbol/state? How do I know whether an element or compound is an aqueous, solid or liquid? I'm always having trouble with questions that ask me to write equation that need to include state. Thank you
Hi @Jaszon99, An element is a species of atoms having the same number of protons in their atomic nuclei (i.e. the same atomic number, Z). There are 118 elements that have been identified, of which the first 94 occur naturally on Earth with the remaining 24 being synthetic elements. (In a simpler words would be that the easiest way to identify them would be if you can find the chemical symbol in the periodic table, then it is an element) (An example of an element would be Na-Sodium which can be found in the periodic table)

A compound is a substance consisting of atoms or ions of two or more different elements in definite proportions joined by chemical bonds into a molecule. The elements cannot be separated by physical means. Water, for example, is a compound having two hydrogen atoms and one oxygen atom per molecule. (H2O)

Hope this helps anyway. :smile:

Superbugs
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Re: O-Level Chemistry

Post by Superbugs » Thu Jul 28, 2016 8:51 am

Urgent!

Any good tutor to recommend that can at least ensure that my daughter can secure at least a B (from fail) in her coming O level? Pls PM me. Tks

KiausuLormee
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Re: O-Level Chemistry

Post by KiausuLormee » Thu Jul 28, 2016 1:10 pm

Hi
Would greatly appreciate if you can email the copy to me.
Email:ohsuanchoo@yahoo.com.sg
Thank you.

raspberrybunny63
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Re: O-Level Chemistry

Post by raspberrybunny63 » Tue Mar 07, 2017 9:59 am

Hi,
I have just read your txt below on the Pure Chem tutor. I am desperately hunting for a good chem tutor for my girl taking "O" level this year. Would you please share with me your niece Pure Chem tutor contact. Thanks a million!

warmest regards,
jenny :?:

spicy wrote:
AdonciaTang wrote:
Mojostar wrote:Hi all,

I'm weak in electrolysis...any way to improve in this area? Any book to recommend? Thanks.
Hi Mojostar. Get a tutor to help u. My niece was also failing in her Pure Chem for a year and she bought all sorts of books to read thinking it would help. It does but its so minimal. After she engaged my DS's tutor, her results improved, because now there is someone who can help to guide her along in her work and teach her the concept which she might get wrong.
Hi
I have PMed you. Would it be possible to share your tutor's contact?
Thanks !

Modernbebe
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Re: O-Level Chemistry

Post by Modernbebe » Tue Jun 27, 2017 8:58 am

Hi,

Can someone help to explain this question from O-level 2010 P2A Q3b?

The answers are:
Universal Indicator Paper 1 is Indigo;pH 10
Universal Indicator Paper 2 is Red; pH 1

How do you determine which exact colour and pH to choose? Can the answers be:
Universal Indicator Paper 1 is Blue;pH 12
Universal Indicator Paper 2 is Orange; pH 3

Thanks in advance.

Image


K.Lim
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Re: O-Level Chemistry

Post by K.Lim » Wed Jul 05, 2017 10:53 pm

Re. the above Exam Question.

Things to recognise:-
1) Ammonia is WEAK alkali (Weak alkali has a ph of 10-11.)
2) HCl (on the right hand side of the tube) is STRONG acid (STRONG acid has a ph 0-1)
3) Universal Indicator color: pH 0-1 is RED; pH 10-11 is DARK BLUE (pH 12 is INDIGO)

Answers to your question:-
1) Better pH 10-11 (every difference of 1 in pH is actually 10x in the actual comparison) but the color CAN BE said as dark blue
2) pH CANNOT be 3 as HCl is strong acid.

K.Lim
KiasuNewbie
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Re: O-Level Chemistry

Post by K.Lim » Wed Jul 05, 2017 10:53 pm

Re. the above Exam Question.

Things to recognise:-
1) Ammonia is WEAK alkali (Weak alkali has a ph of 10-11.)
2) HCl (on the right hand side of the tube) is STRONG acid (STRONG acid has a ph 0-1)
3) Universal Indicator color: pH 0-1 is RED; pH 10-11 is DARK BLUE (pH 12 is INDIGO)

Answers to your question:-
1) Better pH 10-11 (every difference of 1 in pH is actually 10x in the actual comparison) but the color CAN BE said as dark blue
2) pH CANNOT be 3 as HCl is strong acid.

Modernbebe
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Re: O-Level Chemistry

Post by Modernbebe » Mon Jul 10, 2017 2:10 pm

:thankyou:
K.Lim wrote:Re. the above Exam Question.

Things to recognise:-
1) Ammonia is WEAK alkali (Weak alkali has a ph of 10-11.)
2) HCl (on the right hand side of the tube) is STRONG acid (STRONG acid has a ph 0-1)
3) Universal Indicator color: pH 0-1 is RED; pH 10-11 is DARK BLUE (pH 12 is INDIGO)

Answers to your question:-
1) Better pH 10-11 (every difference of 1 in pH is actually 10x in the actual comparison) but the color CAN BE said as dark blue
2) pH CANNOT be 3 as HCl is strong acid.

kitty2
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Re: O-Level Chemistry

Post by kitty2 » Wed Sep 06, 2017 10:04 am

Can anyone advise how to do well for SPA?

Metanoia
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Re: O-Level Chemistry

Post by Metanoia » Wed Sep 06, 2017 3:31 pm

kitty2 wrote:Can anyone advise how to do well for SPA?
Hi there, to clarify, are you referring to the school-based Science Practical Assessment taken by Pure chemistry students or the Science Practical Exams taken by combined chemistry students?

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