Separation of Substances Flashcards

Practice flashcards covering various methods of separating substances, including handpicking, sieving, sedimentation, decantation, and filtration.

What is handpicking?

Handpicking is the method of removing unwanted substances from a mixture by hand, performed on the basis of differences in size, colour, and shape of the particles.

What is the process of threshing?

Threshing is the process of beating stalks to separate grains, such as wheat and rice, from them.

Under what conditions is sieving used for mixtures?

Sieving is used for solid-solid mixtures where the components have different particle sizes.

What is the requirement for a sieve's hole size to effectively separate components?

The sieve's hole size must be between the sizes of the two components for separation to work.

Why can winnowing not be performed in a closed room?

Winnowing requires moving air or wind to blow the lighter component away, and in a closed room, there is no air movement.

Why is handpicking more appropriate than sieving to separate stones from pulses?

Stones and pulses are similar in size, but handpicking works because stones differ in colour, shape, and appearance and are present in small quantities.

What is sedimentation?

Sedimentation is the settling of heavier, insoluble particles to the bottom of a liquid when left undisturbed.

What are the characteristics of evaporation regarding speed and visibility?

Evaporation is a slow process occurring at normal temperature where no visible change occurs and vapours cannot be seen.

What are the characteristics of boiling regarding speed and visibility?

Boiling is a fast process requiring high heat that produces visible bubbles and vapours.

What is the primary limitation of decantation?

Decantation does not give complete separation because very fine particles that have not fully settled remain suspended in the poured liquid.

How do the two steps of sedimentation and decantation work together?

Step $1$ is sedimentation, where heavier particles settle by gravity; Step $2$ is decantation, where the clear liquid above is carefully poured off by tilting the vessel.

How can oil and water be separated using decantation?

When left undisturbed, oil floats on water because it is lighter and they do not mix; the upper oil layer can then be carefully poured off.

In filtration, what are the residue and the filtrate?

The residue is the solid trapped on the filter, and the filtrate is the clear liquid that passes through the filter pores.

How does churning separate components from curd?

Churning involves rapid stirring or spinning using mechanical force to separate butter, which is lighter and floats to the top, from the liquid buttermilk.

What is magnetic separation?

Magnetic separation is a method that uses a magnet to separate magnetic substances from non-magnetic substances, such as removing iron nails from sawdust.