Question

Classify the following substance into elements, compounds and mixtures:

Water

Answer 1

Water $\left({\mathrm{H}}_2\mathrm{O}\right)$ can be classified as a compound.

• This is because water is made up of two elements combined chemically i.e.; Hydrogen $\left(\mathrm{H}\right)$ and Oxygen $\left(\mathrm{O}\right)$ having a fixed composition of 2:1.
• In the sense that water contains only one type of constituent particles which have identical chemical properties i.e.; $\left({\mathrm{H}}_2\mathrm{O}\right)$ particles, it is a pure substance.
• The properties of the compound (water) are different from its elements (Hydrogen and Oxygen). Example: Water is a liquid whereas Hydrogen and Oxygen are gases.
• Water can not be broken down into its elements by physical processes. So a process like electrolysis (breakdown of a substance using electricity) is required.

Element: An element is a pure substance that cannot be split into simpler substances.

• Example: Hydrogen $\left(\mathrm{H}\right)$, Copper $\left(\mathrm{Cu}\right)$ etc.

Compound: A compound is a pure substance in which elements combine chemically in a fixed composition to give a compound.

• They can be broken down into elements that make up the compound by using chemical or electrochemical methods.
• The properties of the compound are entirely different from the elements from which it is formed.
• Example: Water $\left({\mathrm{H}}_2\mathrm{O}\right)$, Common salt i.e.; Sodium chloride $\left(\mathrm{NaCl}\right)$

Mixture: When two or more substances (elements or compounds or an element and compound) are mixed in any proportion.

• The components of a mixture can be separated by physical methods of separation.
• Example: A mixture of Sand and Iron $\left(\mathrm{Fe}\right)$ can be separated by using a magnet (physical process) where Iron gets attracted to the magnet leaving behind sand.