Chemistry Journal

Chemistry blog by Mok Wei Tong
Class:207 Teacher: Mrs Tay York Lan

Date: 19th January 2013

Input

Output

Elements, Compounds and Mixtures

An element is a pure substance that cannot be split up into two or more simpler substances by chemical processes or by electricity.

-->with a total of 118 elements found on earth for now(periodic table)
--> basic units are atoms, but some molecules are considered elements too.
(monoatomic-->noble gasses, diatomic-->O2, etc., triatomic,-->O3, etc. polyatomic molecules-->O4, S8, etc.)

Element can be further classified as:
-Metal
Metals are shiny, solids at room temperature, malleable, sonorous, ductile, and has a high melting point and boiling point(except sodium, potassium and mercury), are good conductors of heat and are good conductors of electricity in all states of matter.

-Non-metals
Non-metals are dull if they are solid(non-lustrous), volatile substances/solids with low melting points at room temperature point(normal pressure)--> pressure affects boiling/melting point, brittle if solid, poor conductors of heat(except carbon in the form of graphite and diamond), and are poor conductors of electricity(except carbon in the form of graphite)

-Metalloids
Metalloids are elements that have both metal and non-metal properties(that are elements near the staircase of the elements)

A compound is a pure substance that contains two or more elements chemically combined.
Bold words are those characteristics different from that of Mixtures.

Compounds also have a fixed composition(ratio) to make a certain compound. Different ratios of the same kind of element will not combine to form the same compound.

Apart from heating to combine two or more elements to form compounds, heating can also be used to break down compounds into elements/ simpler compounds. This is called thermal Decomposition. Another method that can be used is by using electricity.

Mixtures are formed when two substances are added together without chemical bonds being formed.

Chemical means vs. Physical means
Chemical means require heating, lighting, etc.
Physical means do not require any reaction to take place.

The element song we watched in class:

http://www.youtube.com/watch?v=zGM-wSKFBpo

Elements:

Microscopic view of atoms of an element (gas phase).

Microscopic view of molecules of an element (gas phase).

diatomic molecules(also considered an element)

Note that an element:

consists of only one kind of atom,
cannot be broken down into a simpler type of matter by either physical or chemical means, and
can exist as either atoms (e.g. argon) or molecules (e.g., nitrogen).

The two nitrogen ions move as a unit, and they are also similar, so they are elements.

Microscopic view of molecules of a compound (gas phase).

Compounds

Note that a compound:

consists of atoms of two or more different elements bound together,
can be broken down into a simpler type of matter (elements) by chemical means (but not by physical means),
has properties that are different from its component elements, and
always contains the same ratio of its component atoms.

Microscopic view of a mixture of two elements and a compound (gas phase).

Mixtures
Note that a mixture:

consists of two or more different elements and/or compounds physically intermingled,
can be separated into its components by physical means, and
often retains many of the properties of its components.

-->Output

Elements	Compounds
· Cannot be separated by any means into simpler substances · Do not need a fixed composition to make up an element · Made up of one kind of atom · Same properties of the original elements · Basic unit is both a molecule and an atom	· Can be separated by chemical means into simpler substances · Need a fixed composition to make up a compound · Made up of two or more different kinds of element · Different properties of the original elements · Basic unit is molecule


Practical work Bunsen Burner practical Iron sulfide practical

Separation Techniques

Input

Output

The techniques are used to separate the mixture based on the properties of the constituents.
In nature, most substances are mixtures
Mixtures need to be separated into pure substances for

-Characterization

-Identification

-Make important products