Page 51 - ICSE Chemistry 8

Activity 3.1

Aim: To separate the components of a mixture by sieving
Materials required: Some fl our, some pulses, container, sieve
Procedure

• Take some fl our and pulses, and mix them.
• Take a container and place a sieve over it. mixture of fl our
and pulses
• Put the mixture of fl our and pulses on the sieve.
• Shake the sieve over the container.

Observa on: The fl our passes through the holes in the sieve
into the container whereas the pulses are le behind on the sieve.
Conclusion: This shows that a mixture containing components of diff erent sizes can be separated by
sieving.

Winnowing

The method of separa ng components of a mixture using wind or moving air is
called winnowing.

The principle of this technique is diff erence in the mass of components under the
ac on of gravity. The mixture contained in a basket is allowed to fall from a height.
The heavier component falls almost straight downwards and the lighter component
is blown away and forms a separate heap at a distance. Heavier par cles such as
grains are separated from lighter par cles such as husk and chaff using winnowing. Fig. 3.3: Winnowing

Activity 3.2

mixtures of
Aim: To separate the components of a mixture by winnowing pulses and
small pieces
Materials required: Some gram, small bits of paper, a tray, a of paper
tub, a pedestal fan
Procedure

• Take some gram and mix them with bits of paper.
• Take a tray and put the mixture prepared in this tray.
• Place a large tub on the fl oor.
• Place a pedestal fan near the tub and switch on the fan.
• Stand in front of the fan as shown in the fi gure and hold the tray high directly above the tub.

• Allow the mixture to fall slowly into the tub. Keep shaking the tray from me to me as the mixture falls.
Observa on: The bits of paper are blown away and the gram fall into the tub.

Conclusion: This shows that components of a mixture having diff erent masses can be separated by
winnowing.

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