Question

Classify the following substances into elements, compounds and mixtures:

(i) air (ii) common salt (iii) iron fillings (iv) marbles (v) oxygen (vi) milk (vii) zinc (viii) bronze (ix) sand (x) water

Answer 1

Classifying the following substances into elements, compounds and mixtures:

Elements:

1. Elements are substances that cannot be reduced to simpler substances by normal chemical means and that are composed of same type of atoms.
2. Out of the given options iron fillings, oxygen and zinc are elements as they cannot be broken further and are made up of same kind of atoms.

Therefore, (iii) iron filling, (v) oxygen and (vii) zinc are classified as elements.

Compounds:

1. Compounds are pure substances made up of two or more elements combined together in a fixed proportion. The elements cannot be separated by physical methods.
2. Common Salt ($\mathrm{NaCl}$) and water (${\mathrm{H}}_2\mathrm{O}$ ) are examples of compounds.

Therefore, (ii) common salt and (x) water are classified as compounds.

Mixtures:

1. A mixture is a substance in which two or more pure substances are mixed together in an undefined proportion which can be separated by simple physical methods.
2. Air is a mixture of nitrogen, oxygen and other gases. Similarly, marbles, milk, bronze and sand are also examples of mixtures.

Therefore, (i) air, (iv) marbles, (vi) milk, (viii) bronze and (ix) sand are classified as mixtures.