Nota Terkini

Monday, January 04, 2010

[Science Form 1] Oxygen & Carbon Dioxide

Oxygen (O2) and carbon dioxide (CO2) are two of the most important gases in air.

Oxygen is the third most abundant element in the universe and makes up nearly 21% of the earth's atmosphere.

Joseph Priestly and Carl Wilhelm Scheele both independently discovered oxygen in 1774, but Priestly is usually given credit for the discovery.

The name oxygen was created by Antoine Lavoisier, who incorrectly believed that oxygen was necessary to form all acids.

Carbon dioxide is a chemical compound, the molecule of which consists of one atom of carbon joined to two atoms of oxygen (CO2).

It was first called "fixed air" by the Scottish chemist Joseph Black, who obtained it through the decomposition of chalk and limestone, and recognized that it entered into the chemical composition of these substances.

What are the properties of oxygen and carbon dioxide? Let's take a look at the table below.

Property

OXYGEN

CARBON DIOXIDE

Colour

Colourless

Colourless

Smell

Odourless

Odourless

Taste

Tasteless

Sour

Solubility in water

Slightly soluble

More soluble then oxygen

Solubility in sodium hydroxide solution

Not soluble

Very soluble

Combustion and burning

Supports combustion but does not burn

Does not support combustion and does not burn

Effect on lime water

No change

Turn chalky

pH

Neutral

Acidic

Test for presence of gas

Rekindles glowing wooden splinter

Turn lime water chalky


1 comment:

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