Separation of Mixtures – Sublimation
7 Minutes
Separation of mixtures by sublimation for students: learn how naphthalene is extracted and purified from impurities. A short science lesson in English.
- Extracting naphthalene from crude oil tar
- Using a glass funnel, filter paper, and cotton to trap impurities
- Heating naphthalene into vapour to separate it from solid waste
What this lesson teaches
Sublimation is a method used for the separation of mixtures containing two different solids, where heat causes one substance to turn into vapor and separate from solid waste. It is used in science and manufacturing to extract and purify substances such as naphthalene from crude oil products and unwanted dust particles.
Origin of naphthalene from crude oil
Petroleum crude oil is refined to produce fuels like petrol, diesel, and kerosene, leaving behind a sticky substance that is a mixture of solid and liquid. This thick material is the tar commonly used for laying roads, and raw naphthalene is extracted directly from it. The primary challenge for industries is extracting this fragrant naphthalene from the road tar without leaving behind unwanted solid impurities.
Separating the mixture in a laboratory
- A clean piece of filter paper is folded into a cone shape and fitted inside a glass funnel.
- A small piece of cotton cloth is used to plug the narrow end of the glass funnel tightly.
- The entire funnel is turned upside down and placed directly over the vessel holding the solid mixture.
- The unwanted solid waste and dust particles remain trapped down below, separating the pure naphthalene from the dirt.
Purification in large-scale industries
Commercial manufacturing plants that produce naphthalene balls use this separation technique on a massive scale. Raw naphthalene powder mixed with various impurities is loaded into a large heating chamber. As heat is applied steadily to the mixture, the solid naphthalene transforms into vapor. This vapor separates completely from the solid waste and rises toward the top of the chamber.
Separation of solid mixtures
- The sublimation method is specifically designed to separate two different solid materials that have been mixed together.
- Heating the mixture causes only the target solid to change phase into a rising vapor.
- The non-vaporizing impurities and dust particles are left behind in the bottom container.
- This process divides an unrefined heap of mixed solids into pure, individual components.