Question

Explain why milk is regarded as a mixture and not as a pure substance.

Answer 1

Milk is regarded as a mixture and not as a pure substance.

• This is because milk contains various substances namely fats globules, water, milk proteins, milk sugar, etc.
• Fat can be separated from milk using the physical method of centrifugation.
• Further, it is a heterogeneous mixture as the constituent particles are not uniformly present throughout.

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.

For a substance to be regarded as a pure substance, it needs to be comprised of only one kind of particle. These particles can comprise of only one element (in other words, one type of atom like in Hydrogen gas $\left({\mathrm{H}}_2\right)$ or more than one element (in other words, more than one type of atom-like in Water $\left({\mathrm{H}}_2\mathrm{O}\right)$.