Classify the following substance as element, compound or mixture:

Gold

Gold $\left(\mathrm{Au}\right)$ can be classified as an element.

• This is because gold is made up of atoms i.e.; gold particles (atoms) only.
• Gold contains only one type of constituent particle i.e.; gold atoms.
• Gold atoms cannot be broken down into simpler substances.

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

• Example: 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 the use of a magnet (physical process) where Iron gets attracted to the magnet leaving behind the sand.