What are thermal decomposition reactions? Explain with an example.

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Hint: The word thermal is related to the heat and the word decomposition means breakdown i.e. in thermal decomposition reactions, a compound breaks into two or more parts. Now with the help of this you can easily answer the given statement.

Complete answer:
By the Thermal Decomposition reactions, we mean those reactions in which the larger substances or the compounds ( whether organic or inorganic) break down into two or more substances or compounds or products in the presence of heat. Consider the general reaction as:
$A\xrightarrow{\Delta }B+C$
In this reaction, the compound A splits into two compounds i.e. B and C in the presence of heat.
The examples of thermal decompositions reactions are as follows:
(1) Decomposition reaction of zinc carbonate: When zinc carbonate is exposed to heating, it undergoes decomposition reaction resulting in the formation of the zinc oxide and carbon dioxide. The reaction is supposed to occurs as:
(2) Decomposition reaction of alkanes: The higher alkanes when exposed to heating, undergoes decomposition reaction and results in the formation of lower alkanes along with the formation of alkenes. The reaction is supposed to occurs as:

Note: The thermal decomposition reaction of the alkanes is also known as the crackling reaction. It is so because when higher alkanes are exposed to the heat, they break down into the lower alkanes or alkenes and produce the crackling sound .This reaction is very important to produce lower alkanes from the higher ones or to produce many products from one single compound.