METHODS OF SEPARATING SUBSTANCES Q/A

1. Fill in the blanks:

(a) Air is a mixture of …………….

(b)During the monsoons, …………………….. is swirled through drinking water.

(c)……………………..  is sublimating substance.

2. Answer in brief:

(a) How are mixtures formed?

(b) Why do we need to separate substances from their mixtures?

(c) Name the methods used to separate substances from their mixture.

(d)What is sublimation?

3. Do as directed:

(a) Write the apparatus used and observations made in the experiment done to separate sand and salt from their mixture.

(b) Write the procedure followed and draw the diagram of the apparatus used in the experiment for separating a sublimating substance from a mixture.

4. Give as many as you can for the following:

 (a) Separating light material from grains.

(b) Removing weevils from grains.

(c) Picking stones from grain.

(d) Cleaning grain which has lot of soil mixed in it.

(e) Cleaning muddy water.

5. Classify into sublimating and non-sublimating substances:

Sand, iodine, salt, alum, sal ammoniac, sugar, camphor, water, oil, naphthalene, turmeric.

6. Which method will you use to separate the substances in each of the following mixtures?

(a) water + alum

(b) camphor + sand

(c) water + soil

(d) tea + tea leaves.

1. Fill in the blanks:

(a) Air is a mixture of gases.

(b)During the monsoons, alum crystal is swirled through drinking water.

(c) Iodine or camphor or sal ammoniac or naphthalene is sublimating substance.

2. Answer in brief:

(a) How are mixtures formed?

Ans:  If any of the substances whether solid, liquid or gaseous, are mixed together, we get a mixture.

Example : Air around us  is a mixture of gases.

(b) Why do we need to separate substances from their mixtures?

Ans: 1) If any of the substances whether solid, liquid or gaseous, are mixed together, we get a mixture.

2) We need to separate substances from its mixture for our convenience and according to our need.

3) For purification of substance that has to be consumed.

4) For reusing certain constituent from the mixture.

Example : purification of water, separation of grains from crop etc.

(c) Name the methods used to separate substances from their mixture.

Ans: 1) Various methods are used to separate substances from its mixture.

2) The method used depends upon various properties of the constituents.

3) Different methods to separate substances from mixture are, threshing, winnowing, sifting, picking, settling, filtration, sublimation, churning, magnetic separation, centrifugation etc.

(d)What is sublimation?

Ans : 1) When some solids are heated, they change straight into a gas and not into a liquid first, this is called sublimation.

Example : Iodine, sal ammoniac, camphor, naphthalene are substances that sublimate.

3. Do as directed:

(a) Write the apparatus used and observations made in the experiment done to separate sand and salt from their mixture.

Ans: Apparatus: Sand, salt, spoons, a cup of water, strainer, beaker, stirrer, evaporating dish.

Observation: 1) From  mixture of salt and sand, salt dissolves in water. 2) Sand will remain on the strainer while salt water will flow out as filtrate. 3) After heating the filtrate, water evaporates leaving salt crystals.

(b) Write the procedure followed and draw the diagram of the apparatus used in the experiment for separating a sublimating substance from a mixture.

Ans : 1)In a porcelain bowl, take a mixture of sal ammoniac powder and sand. 2) Plug the tube of a funnel with cotton wool and place it upside down over the mixture. 3) Arrange the apparatus as shown in the figure. 4) Slowly heat the mixture. 5) After some time see particles of sal ammoniac deposited on the inside of the funnel and on the cotton wool plug. 6) Sal ammoniac is a sublimating substance hence Heating caused the sal ammoniac to sublimate and rise into the funnel. 7) When it cools, it changes back into a solid and gets deposited on the cotton plug. 8) If we continue to heat the mixture, all the sal ammoniac will sublimate and separate from the mixture.

4. Give as many as you can for the following:

 (a) Separating light material from grains. -------------- winnowing, sifting

(b) Removing weevils from grains.  -------------- Sifting, picking

(c) Picking stones from grain. --------------  sifting, picking.

(d) Cleaning grain which has lot of soil mixed in it. ---------- Sifting.

(e) Cleaning muddy water. ---------- Settling, decantation , filtration.

5. Classify into sublimating and non-sublimating substances:

Sand, iodine, salt, alum, sal ammoniac, sugar, camphor, water, oil, naphthalene, turmeric.

Ans:  Sublimating substances: iodine, sal ammoniac, camphor, naphthalene.

         Non sublimating substances : sand, salt, alum, sugar, water, oil, turmeric.

6. Which method will you use to separate the substances in each of the following mixtures?

(a) water + alum ---------------------- Evaporation

(b) camphor + sand ------------------- Sublimation

(c) water + soil ------------------------- Settling and decantation

(d) tea + tea leaves. ------------------ Filtration