Combustibility: is the property that a compound has to burn. Most substances that undergo combustion are of organic origin. That's why we say organic compounds are great fuels.
Examples:
- The gas we use in the kitchen (LPG) is composed of hydrocarbons, therefore it is organic.
- Fuel alcohol for automobiles - formula ethanol (CH3CH2OH) - is of organic origin.
Melting and boiling temperature
At room temperature, organic compounds are in three physical states: solid, liquid and gas. This proves that their melting and boiling points are lower than those of substances of inorganic origin, since most inorganic compounds are in solid state.
Compounds of organic origin have weaker intermolecular interactions and therefore have lower boiling and melting temperatures.
Examples:
- Butane gas (C4H10): The gas used in lighters has low melting (-138 °C) and boiling (0 °C) temperatures.
- Ethanol: combustible liquid with melting temperature (-117 °C) and boiling (78.3 °C).
Now compare these values with the melting (T.F) and boiling (T.E.) temperature of a solid inorganic compound, table salt (Sodium Chloride -NaCl).
T. F of salt: 801 °C
YOU. of salt: 1413 °C
As we can see, the inorganic salt used in our food has melting and boiling temperatures well above T.F and T.E. of organic compounds.
Solubility in water
This property is related to the polarity of the organic molecule.
Non-polar organic compounds: they are practically all insoluble in water. Following the rule: "Like dissolves like", we see the reason. As water is polar, it does not dissolve non-polar compounds such as gasoline, kerosene, diesel oil, etc.
Polar organic compounds: These can be dissolved in water. Examples: sugar, regular alcohol, acetone etc.
By Líria Alves
Graduated in Chemistry
Source: Brazil School - https://brasilescola.uol.com.br/quimica/caracteristicas-gerais-dos-compostos-organicos.htm