Question

Classify the following as element, mixture or compound:

18-carat gold

Answer 1

18 carat Gold $\left(\mathrm{Au}\right)$ can be classified as a mixture.

• 18 carat gold means 18 parts gold and 6 parts of some other metal like Silver $\left(\mathrm{Ag}\right)$, Copper $\left(\mathrm{Cu}\right)$ etc.
• Two elements are present i.e.; gold and silver/ copper which are not chemically combined but rather in a physically combined state.
• In this, the properties of the components i.e.; gold and other metal is retained.

It is not an element, because more than one type of element is present.

It is not a compound because the components are not present in a chemically combined form.

Element: An element is a pure substance that cannot be split into simpler substances and comprises of only one type of atoms.

• Example: Hydrogen $\left({\mathrm{H}}_2\right)$, 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 the use of a magnet (physical process) where Iron gets attracted to the magnet leaving behind sand.