Question

State why a direct combination reaction is called a – ‘synthesis reaction’.

Answer 1

When two or more substances [element with element or element with compound or compound with another compound] combine to form a new compound with new properties. Hence direct combination is called a ‘synthesis reaction’.
Example: Hydrogen (a gas) + Oxygen (a gas) combines to form water (liquid).
\[\ce{2H2 + O2->2H2O}\]