ICSE Class 7 Answered

    A chemical reaction in which two or more substances combine to form a single product is called a combination reaction or synthesis.

    Example: When iron and sulphur are heated together, they combine to form a single product, iron sulphide.

                              2Fe(s)     +     S(s)    →              FeS (s)

                                 Iron         Sulphur                Iron sulphide

2. Displacement Reaction:

    Reactions in which the more reactive element displaces the less reactive element from its compound are called displacement reactions.

    Zinc displaces copper in copper sulphate to form zinc sulphate.

               Zn(s)   +     CuSO4(aq)          →                   ZnSO4(aq)     +       Cu(s)