Why can t some objects burn and which cannot?

Combustion requires two conditions, one is that the ignition point of the object needs to be reached, and the other is that it needs to be in full contact with oxygen.

Oxygen in the air accounts for just over 20 percent, and oxygen is scarce for the combustion of some objects, so it cannot be burned. For example, iron can't burn in the air, but in oxygen, it can burn, and it's very violent, and Mars is cheap, generating ferric tetroxide!

It can be explained from a chemical thermodynamic point of view; If the Gibbs free energy of the reaction is 0, the reaction must not take place including combustion.

Some react Gibbs free energy <0. However, the reaction conditions are demanding and can be explained from the perspective of reaction kinetics. For example, water produces hydrogen and oxygen, and Gibbs free energy < 0, but it does not decompose at room temperature, and can only be used with electricity.

Combustion (in junior high school chemistry) refers to a violently luminescent, exothermic reaction with oxygen.

Some substances cannot react with oxygen at all (such as carbon dioxide and other most ** oxides) and certainly cannot be burned.

Some substances react with oxygen, but not as violently (e.g. nitrogen, ammonia) and do not count as combustion.

Because the structure is stable and reactive substances are required.

The universal rule is: in oxygen.

For elemental matter: alkali metals (lithium, sodium, potassium, rubidium, cesium, francium), alkaline earth metals (magnesium, calcium, strontium, barium), hydrogen, carbon can be burned (if the oxygen concentration is large, aluminum, zinc, etc. can also be burned).

For inorganic compounds (sodium chloride, calcium oxide, etc.): almost all are non-flammable, excluding a few compounds (e.g. azide, ammonium salt, can **).

For organic compounds (ethanol, methane, benzene, etc.): almost all are flammable, excluding a few compounds (tetrafluoroethylene, carbon tetrachloride, etc.) where hydrogen is completely replaced

Mixture: look at the proportion of combustible and non-combustible, if the proportion of combustibles is large, it is basically combustible (silk, cotton), and the proportion of non-combustibles is non-combustible (glass fiber blended fabric).

Most inorganic compounds cannot be burned, such as sodium chloride (table salt), water, etc., and some mixtures cannot be burned, such as glass, bricks, stones, asbestos, etc.

The universal rule is: in oxygen.

For elemental matter: alkali metals (lithium, sodium, potassium, rubidium, cesium, francium), alkaline earth metals (magnesium, calcium, strontium, barium), hydrogen, carbon can be burned (if the oxygen concentration is large, aluminum, zinc, etc. can also be burned).

For inorganic compounds (sodium chloride, calcium oxide, etc.): almost all are non-flammable, excluding a few compounds (e.g. azide, ammonium salt, can **).

For organic compounds (ethanol, methane, benzene, etc.): almost all are flammable, excluding a few compounds (tetrafluoroethylene, carbon tetrachloride, etc.) where hydrogen is completely replaced

Mixture: look at the proportion of combustible and non-combustible, if the proportion of combustibles is large, it is basically combustible (silk, cotton), and the proportion of non-combustibles is non-combustible (glass fiber blended fabric).

What occurs when an object is burned is an exothermic and luminescent chemical reaction, which makes the large chain reaction process extremely complex, the chain reaction of free radicals is the essence of the combustion reaction, and light and heat are the physical phenomena that occur during the combustion process. During combustion, momentum, heat and mass are transferred between fuel, oxygen and combustion products, resulting in a complex structure of flames, which consists of multi-component concentration gradients and non-isothermal two-phase flows.

Oxygen (oxygen), chemical formula O2. Chemical formula: , colorless and odorless gas, the most common elemental form of oxygen.

Melting point, boiling point -183 . Not easily soluble in water, about 30ml of oxygen is dissolved in 1L of water. In the air, oxygen accounts for about 21%.

Liquid oxygen is sky blue. Oxygenation is a blue crystal. At room temperature, it is not very active imitation silver, and it is not easy to interact with many substances.

However, it is very active at high temperatures and can be directly combined with a variety of elements, which is related to the electronegativity of oxygen atoms second only to fluorine. Tansun.

What is total combustion?

Answer: Any new substance that can not continue to burn after the combustion of a substance is called complete combustion.

27. What is incomplete combustion?

Answer: After the combustion of any substance, the new substance that can be burned after the mass is burned is called the coarse, and this kind of combustion is called incomplete combustion.

Question 1: Why can't some organic matter be burned, and why is it still called organic matter, thank you! Organic matter is mainly composed of oxygen, hydrogen and carbon slag.

Organic matter is the material basis for the production of life. Fats, amino acids, proteins, sugars, heme, chlorophyll, enzymes, hormones, etc. The metabolism of organisms and the genetic phenomena of organisms are involved in the transformation of organic compounds.

In addition, many substances that are closely related to human life, such as oil, natural gas, cotton, dyes, chemical fibers, natural and synthetic medicines, etc., are organic compounds.

Organic compounds are generally combustible except for a few. But the corresponding conditions must be met before He Chun can be done. Some combustion requires more oxygen, and the air is not enough to support it; Some combustion requires a higher temperature, and some even hundreds or thousands of degrees of high temperature will burn like a rush; Others burn more harshly and require the addition of other substances (i.e., catalysts) in addition to temperature oxygen.

So it's not like you can't burn if you don't see it.

Carbon dioxide is an inorganic substance.

Organic matter is a compound that must contain carbon elements, but carbon monoxide, carbon dioxide, carbonate, bicarbonate, carbonic acid, metal carbides, etc. should be excluded. Because the properties of these types of substances are more in line with the characteristics of inorganic substances, these types of carbon-containing compounds are classified as inorganic substances.

Carbon dioxide cannot be burned, but under certain conditions it can act as an accelerant, such as magnesium bars, which can be burned in carbon dioxide. It's just that there is almost no research in junior high school.

Coal is precisely a mixture, and organic matter is present in the components that compose it. However, when asked about the combustion of coal in the junior high school exam, the main chemical reaction is the chemical reaction that occurs under the condition of ignition of carbon and oxygen, c+O2===CO2

For example, carbon in inorganic matter can be burned, and sulfur can also be burned. Therefore, it is wrong to say that organic matter can burn, but inorganic matter cannot burn.

Carbon dioxide is an inorganic substance, and organic matter refers to a substance containing three elements: carbon, hydrogen, and oxygen.

There are more, but there are two situations, completely non-burning and self-extinguishing from the fire, most thermosetting plastics are non-combustible, like phenolic resins, and self-extinguishing from the fire have halogenated hydrocarbon polymers, polyvinyl chloride, these.

Generally, polyhalogenated hydrocarbons are not easy to burn, the most typical one: carbon tetrachloride, which can be used as a flame retardant.