Question

Classify the following as a physical or chemical change: Burning of coal

Answer 1

Hint:
To answer this question, you should recall the concept of physical change and chemical changes. A substance is said to undergo a physical change when only the physical properties of the reactant change while chemical change refers to a substance combined with another to form a new substance.

Complete step by step solution:
The major differences between chemical and physical change can be tabulated as below:

Physical Change	Chemical Change
When a substance undergoes a physical change, its composition remains the same despite its molecules being rearranged.	When a substance undergoes a chemical change, its molecular composition is changed entirely. Thus, chemical changes involve the formation of new substances.
Physical change is a temporary change.	A chemical change is a permanent change.
A Physical change affects only physical properties i.e. shape, size, etc.	Chemical change both physical and chemical properties of the substance including its composition
Some examples of physical change are freezing of water, melting of wax, boiling of water, etc.	A few examples of chemical change are digestion of food, burning of coal, rusting, etc.
In a physical change, no new substance is formed.	A chemical change is always accompanied by one or more new substances.

When burned, the carbon is converted to carbon dioxide and the hydrogen to water. Each of those reactions produces a slightly different amount of heat. This process cannot be reversed and hence, the burning of coal is a chemical change.

Note:
You should know about the different types of reaction.
Combination reaction: A combination reaction (also known as a synthesis reaction) is a reaction where two or more elements or compounds (reactants) combine to form a single compound (product). Example: \[Cao + C{O_2} \to CaC{O_3}\]​, in this reaction calcium oxide is combined with carbon dioxide to form calcium carbonate.
Decomposition reaction: A Decomposition reaction is a reaction in which a single component breaks down into multiple products. Certain changes in energy in the environment have to be made like heat, light or electricity breaking bonds of the compound. Consider the example of the decomposition of calcium carbonate\[CaC{O_{3}} \to CaO + C{O_2},\] in this reaction calcium carbonate is decomposed to calcium oxide and carbon dioxide.
Displacement reaction: A displacement reaction is the one wherein the atom or a set of atoms is displaced by another atom in a molecule.\[Fe\left( s \right) + CuS{O_4}\left( {aq.} \right) \to FeS{O_{4}}\left( {aq} \right) + Cu\left( s \right),\] In this reaction, Fe displaces copper to form ferric sulphate.