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Oxygen and Combustion Gas


Oxygen gas is a gas of fundamental importance for the vital processes of our planet, used in the breath of most living things. Algae and plants also absorb oxygen in respiration, but, through photosynthesis, release this gas, enabling its continuous renewal in the environment.

Most of the inspired oxygen is used by living beings to produce energy that maintains their vital systems.

Now look at the picture.

If we tip a glass over a lighted candle, the flame goes out. The candle goes out because oxygen inside the glass has been used up during the candle burn. Oxygen is therefore required for candle burning. Incidentally, it is required for burning other materials as well. The burning process is called combustion.

In 1783, the French chemist Antoine Lavoisies (1743-1794) explained these phenomena: In combustion occurs the combination of oxygen with other substances, releasing large amount of heat in a short time.

When the car engine runs, for example, gasoline combines with the oxygen in the air. Gasoline or the other substance being burned is called fuel, and oxygen is called oxidizing. Oxidant is therefore the substance that causes combustion.

In the case of the lit candle, the oxidizer is the oxygen in the air. The fuel is the candle paraffin. But to start combustion, you need to heat the fuel. In the case of the candle, we light the wick with a match. The heat of the wick flame warms the paraffin that combines with oxygen and is burned.

Combustion releases chemical energy that is stored in the fuel.. This energy appears in the form of heat and light. With the energy of combustion, humans drive gasoline, gas, diesel or alcohol vehicles and cook food on the stove. This energy can also be released from thermoelectric plants, which transform energy from fuels such as coal and oil into electricity.

After the candle burns out, a little paraffin is left. But the amount left over is much smaller. Where then did the missing paraffin go?

Combustion transforms the fuel, which in this case is paraffin, into water vapor and carbon dioxide. What happens here is called chemical transformation or chemical reaction. The substances in paraffin become other substances: carbon dioxide and water.

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Oxygen and cellular respiration

An animal kept in a closed container dies soon - even if there is enough food. Why?

Almost all living things use oxygen in a process that releases energy for their activities. Without oxygen, most living things can't get enough energy to stay alive. This process is called cellular respiration.

Let's see how it occurs:

The process that involves oxygen entering our lungs and carbon dioxide output is called pulmonary respiration. From the lungs air enters and, through the bloodstream, is carried into microscopic structures that make up our body, the cells. In cells occurs cellular respiration, where oxygen combines with food chemicals (mainly sugar, glucose) and releases energy. In addition, carbon dioxide and water are also produced.

See a summary of cellular respiration:

glucose + oxygen -------> carbon dioxide + water

The difference between cellular respiration and combustion

Both cellular respiration and combustion of most substances produce carbon dioxide and water vapor. But breathing is a more complicated and time-consuming process than combustion: breathing occurs in stages. Glucose, for example, is transformed into a series of substances to become carbon dioxide and water.

If breathing occurred in the same way as combustion, energy would be released too quickly, and heat would cause the body's temperature to rise so much that it would cause death. Instead, in breathing the energy is gradually released without the cell temperature rising much.