Classification of Reactions

Introduction
Chemical reactions can be classified into two main categories: chemical changes and physical changes. In chemical changes, new substances with different chemical properties are formed, while in physical changes, the substances involved do not change their chemical properties, only their physical state or arrangement is altered.

(a) Reaction of Iron with CuSO4
This reaction involves the reaction between iron (Fe) and copper sulfate (CuSO4). The iron displaces copper from the copper sulfate, resulting in the formation of iron sulfate (FeSO4) and copper (Cu). This is a chemical change because new substances are formed with different chemical properties than the original substances.

(b) Burning of Magnesium in Air
When magnesium (Mg) burns in air, it reacts with oxygen (O2) to form magnesium oxide (MgO). This is also a chemical change as a new substance with different properties is formed.

(c) Reaction of Zinc with Dilute Sulphuric Acid
Zinc (Zn) reacts with dilute sulphuric acid (H2SO4) to form zinc sulfate (ZnSO4), hydrogen gas (H2), and water (H2O). This is a chemical change as the reactants are transformed into new substances with different chemical properties.

(d) Heating of CuSO4
Heating copper sulfate (CuSO4) causes it to undergo a physical change known as dehydration. The blue hydrated copper sulfate (CuSO4·5H2O) loses water molecules and turns into anhydrous copper sulfate (CuSO4). This is a physical change as no new substances are formed, only the physical state of the substance is altered.

Conclusion
In summary, the reaction of iron with CuSO4 and the reaction of zinc with dilute sulphuric acid are examples of chemical changes as new substances are formed. The burning of magnesium in air is also a chemical change as a new substance is formed. On the other hand, the heating of CuSO4 is a physical change as the substance undergoes a change in physical state without forming new substances.

A,b,c are chemical change and d is physical change