Oxygen, Fire and Breathing

Candle off without blowing it!
Fire Magic Tricks

Our school teacher placed an empty inverted water glass over the small burning candle which soon began to flicker and soon the fire was extinguished. Why?

It was an effective trick to show us pupils how important oxygen is for burning and we still remember that free flow of oxygen is needed for good BBQ fire from the lecture given so many years ago.

But why do we breath?
In order to get oxygen, you moron!
Yes, but why do we breath oxygen, for what we need it? Are we also burning something?
Hmm...

Photosynthesis simplified wikimedia

Oxygen is a chemical element with symbol O and atomic number 8. Its name derives from the Greek roots ὀξύς (oxys) ("acid", literally "sharp", referring to the sour taste of acids) and -γόνος (-gοnos) ("producer", literally "begetter"), because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition. At standard temperature and pressure, two atoms of the element bind to form dioxygen, colorless, odorless, tasteless diatomic gas with the formula O2. This compound is an important part of the atmosphere, and is necessary to sustain terrestrial life.

Because it comprises most of the mass in water, oxygen comprises most of the mass of living organisms (for example, about two-thirds of the human body's mass).

All major classes of structural molecules in living organisms, such as proteins, carbohydrates, and fats, contain oxygen, as do the major inorganic compounds that comprise animal shells, teeth, and bone.

Elemental oxygen is produced by cyanobacteria, algae and plants, and is used in cellular respiration for all complex life.

Ach so! Cellular respiration
Whatever it is...


So ... putting off the burning candle?

The oxygen that a fire needs is used to support the chemical reaction which takes place when something burns. The oxygen is used along with heat to convert the fuel, which typically is composed of hydrocarbons, to mostly carbon dioxide and water. Without the oxygen the fire would die out, because the chemical reaction couldn't take place without it. A fire needs three things in order to remain burning: fuel, an adequate supply of oxygen, and a sufficient heat source.

Oxygen does not itself burns but supports burning.If the burning substance does not get adequate amount of Oxygen the burning of a substance willl b reduced and fire wouldn't rise much.It will blowed off.
Read more: wiki.answers.com

Hmm...
I am not sure if I quite understand yet the chemistry of burning; it apparently the process is not all that simple.
But that oxygen is needed, that I do remember.