Chemistry of You

99% of the mass of the human body is made up of only six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Every organic molecule contains carbon. Since 65-90% of each body cell consists of water (by weight), it isn't surprising that oxygen and hydrogen are major components of the body.

Source : chemistry.about.com/od/periodictableelements/ig/Elements-in-the-Human-Body/

Gold Alloys

When you buy gold jewelry, it isn't pure gold. Your gold is really an alloy, or mixture of metals. The purity or fineness of gold in the jewelry is indicated by its karat number. 24 karat (24K or 24 kt) gold is as pure as gold for jewelry gets. 24K gold is also called fine gold and it is greater than 99.7% pure gold. Proof gold is even finer, with over 99.95% purity, but it is only used for standardization purposes and is not available for jewelry.

So, what are the metals that are alloyed with gold? Gold will form alloys with most metals, but for jewelry, the most common alloying metals are silver, copper, and zinc. However, other metals may be added, especially to make colored gold.

Source : chemistry.about.com/od/jewelrychemistry/a/goldalloys.htm

Mnemonic - The Reactivity / Electrochemical Series

The suggestable mnemonic for the Reactivity Series is :
Please Send Camels, Monkeys And CARBON Zebras with HYDROGEN In Tom's Large Containers of Solid Gold


Please (Potassium)
Send (Sodium)
Camels (Calcium)
Monkeys (Magnesium)
And (Aluminium)
CARBON
Zebras with (Zinc)
HYDROGEN
In (Iron)
Tom's (Tin)
Large (Lead)
Containers 0f (Copper)
Solid (Silver)
Gold

Whereas, for the Electrochemical Series, the suggestable mnemonic is :
Please Send Camels, Monkeys And Zebras In Tom's Large HYDROGEN Containers of Solid Gold

The reactivity series and the electrochemical series are quite similar except for the addition of carbon element and different position of hydrogen element in the reactivity series. Therefore, it is advisable for you to just memorised carbon and hydrogen at heart.

Mnemonic - Diatomic molecules

There are seven elements that are always found as diatomic molecules. The first one is the first element Hydrogen; the rest form a 7 on the periodic table: Nitrogen, Oxygen, Fluorine across, then going down Chlorine (Cl), Bromine, Iodine.

Suggestable mnemonic : I Have No Bright Or Clever Friends

The Periodic Table of Elements

Chemical formula or Chemical equation??

Many students get confused of chemical formula and chemical equation. Here, I will show a few examples of chemical formulae and equations and their descriptions. Hopefully, this will help you to distinguish between the two.

Chemical formula
A chemical formula tells us the composition of a compound in a short form but understandable to anyone with, at least, basic chemistry. We have a few types of chemical formulae such like :



Chemical equation
Meanwhile, a chemical equation describes a chemical reaction, which means it describes the interaction between reacting chemical substances (called reactants) to produce new chemical substances (called products). There are also a few types of chemical equations, namely :



Remember to balance the chemical equations every time you write them.

Using the terms REACTIVITY and ELECTROPOSITIVITY correctly

REACTIVITY :

Table below shows the observation of an experiment to study the reactivity of metals X , Y and Z with oxygen. Metal powders of X , Y and Z are heated in a flow of oxygen. Potassium manganate(VII) powder is used as the source of oxygen.



Q : Based on the observation in the above table, arrange
the reactivity of metal X, Y and Z in ascending order.
A : X, Z, Y

Explanation :
The more vigorous the reaction the more reactive the metal. Vigorousness in a reaction indicates the reactivity of a substance. Vigorousness is determined through observation such as brightness of flame or glow, speed of the reaction, etc. For the above case, the brighter the flame the more reactive the metal. Thus, the higher its position in the Reactivity series of metals with oxygen.

In F4 and F5 Chemistry syllabus, the term reactivity is mainly used in
i) Determining empirical formula of metal oxide (F4 - Chap 3)
ii) Comparing reactivity of Group 1 elements (F4 – Chap 4)
iii) Comparing reactivity of Group 17 elements (F4 – Chap 4)
iv) Reaction between metals and oxygen, Reactivity
series (F5 – Chap 3)
v) Reaction between carbon / hydrogen with metal oxides (F5–Chap 3)
vi) Reaction between carbon dioxide / water with metal (F5–Chap 3)
vii) Extraction of metals (F5 – Chap 3)


ELECTROPOSITIVITY :

Diagram below shows the set up of apparatus of a chemical cell.



Q i) State the negative terminal
A : Magnesium

Q ii) Explain your answer in Q(i).
A : Magnesium is more electropositive than copper / Magnesium is
higher than copper in the electrochemical series

Explanation :
Metal that acts as a negative terminal must be a metal with higher tendency to donate electrons. Between magnesium and copper, magnesium loses electrons more easily than copper. So, magnesium is said more electropositive. The term reactivity is not suitable to be used here because the process of losing electrons in the chemical cell does not show any vigorousness.

In F4 and F5 Chemistry syllabus, the term reactivity is mainly used in
i) Comparing electropositivity of Group 1 elements (F4 – Chap 4)
ii) Comparing electropositivity of elements across a period
in the Periodic Table (F4 – Chap 4)
iii)Determining the negative terminal of a voltaic cell (F4 - Chap 6)
iv) Displacement of metal from its salt solution (F4 – Chap 6 & F5 – Chap 3)


ELECTRONEGATIVITY :

Table below shows three pairs of chemicals.



Q i) Put a tick (/) in the box beside the pair of chemicals which will
undergo a displacement reaction. Explain your answer.
A : Chlorine is more electronegative than iodine / Chlorine is higher
than iodine in the group 17

Explanation :
It goes the same with the term electronegativity. Electronegativity means a measurement of the strength of the atom of an element to attract electrons towards its nucleus. The atomic size of chlorine is smaller than iodine. Therefore the strength of the nucleus of chlorine to attract electrons is stronger than iodine. Thus, chlorine is said more electronegative than iodine. That is why chlorine is able to displace iodine from its halide solution.
In addition, the reaction also does not show any vigorousness, that is why the term reactivity is not suitable to be used to explain the reaction.

In F4 and F5 Chemistry syllabus, the term reactivity is mainly used in
i) Comparing electronegativity of Group 17 elements (F4 – Chap 4)
ii) Comparing electronegativity of elements across a period
in the Periodic Table (F4 – Chap 4)
iii)Displacement of halogen from its halide solution (F5 – Chap 3)

Chemistry Form 4 & 5

Berikut adalah beberapa slaid persembahan yang bagus daripada pelajar yang boleh anda download untuk rujukan ataupun nota.

Tingkatan 4
THE PERIODIC TABLE OF ELEMENTS
Group 17
Group 18
ELEMENTS IN A PERIOD
ELECTROCHEMISTRY
TEST FOR CATIONS

Tingkatan 5
Medicine

Strong and weak alkalis

Hari ni ada seorang student tanya sama ada calcium hydroxide masuk kategori strong or weak alkalis.
Lepas cari maklumat, dapatlah disimpulkan bahawa :

Some common strong alkalis include : NaOH, KOH, Ba(OH)2, Ca(OH)2 and Mg(OH)2, LiOH
Weak akali : NH3 solution

Concept of strong and weak base/alkali depend on degree of ionisation of the base/alkali whether involves complete or partial ionisation/dissociation.

Ca(OH)2 and Mg(OH)2 for examples are slightly soluble in water but they are still considered as strong bases/alkalis. It is because what does dissolve is still completely ionised into calcium ion and hydroxide ion. They re still counts as a strong base/alkali because of the complete ionisation ( e.g. Ca(OH)2 ----> Ca2+ + OH- ).

Latihan topikal Tingkatan 4

Anda boleh download latihan-latihan berikut untuk menguji ataupun mengukuhkan kefahaman dalam topik-topik berkenaan. Selamat mencuba!!!
Practice 2 - Matter
Practice 3 - The structure of atom
Practice 4-Mole
Practice 5 - Empirical formula MgO
Practice 6-Empirical formula CuO
Practice 8-Noble gases
Practice 9-Halogens
Practice 10-Elements in a Period
Practice 11-Periodic Table
Practice 12-Alkali metals
Practice 13-Transition elements

Kertas 3 - To construct ECS

Berikut adalah beberapa contoh jawapan soalan struktur kertas 3 yang telah cikgu berikan sebagai latihan masa cuti sekolah (Ogos) yang lalu untuk semakan dan rujukan.

Example 1
Example 2
Example 3
Example 4
Example 5
Example 6
Essay-Example 1
Essay-Example 2
Essay-Example 3
Essay-Example 4
Essay-Example 5
Essay-Example 6

Terima kasih atas sumbangan para pelajar yang tugasan mereka telah terpilih sebagai contoh.

Belajar tajuk Salts dengan lebih mudah

Topik ini tak susah pun. Nota salts yang saya sediakan ni adalah ringkasan bab ni. Jadi pelajar boleh tengok perkara yang perlu dihafal tidaklah begitu banyak dan kenalpasti keyword yang berkenaan.

Rahsianya, ingat yang sedikit. Contohnya, senarai soluble and insoluble salts...ada beberapa salts sahaja yang insoluble - PbSO4, CaSO4, BaSO4, PbCl2, AgCl, semua carbonate salts except Na2CO3, (NH4)2CO3 dan K2CO3. Jadi selebihnya adalah soluble salts. Ingat, nak senang...INGAT YANG SEDIKIT SAHAJA.

Antara keyword yang berkenaan, perkataan crystal dan aqueous solution merujuk kepada soluble salt dan perkataan powder ataupun precipitate biasanya merujuk kepada insoluble salt.

Selamat belajar. Salts.doc

Topik Kertas 2 SPM 2003 - 2008

Berikut adalah topik-topik yang telah diuji dalam soalan-soalan berstruktur kertas 2 Kimia SPM 2003 hingga 2008 untuk rujukan anda :

Berikut pula adalah topik-topik yang telah diuji dalam soalan-soalan esei kertas 2 Kimia SPM 2003 hingga 2008 untuk rujukan anda :

Topik kertas 3 SPM 2003 - 2008

Berikut adalah topik-topik yang telah diuji dalam kertas 3 Kimia SPM 2003 hingga 2008 untuk rujukan anda :