GSEB Class 6 Science Solutions Chapter 5 પદાર્થોનું અલગીકરણ

Chapter 5: Separation of Substances

Textbook Questions and Answers

Question 1. શા માટે આપણે મિશ્રણના વિવિધ ઘટકોને અલગ કરીએ છીએ? બે ઉદાહરણ આપો.
Answer: We separate different components from a mixture for a few key reasons:
1. To remove unnecessary and harmful components from the mixture. For instance, we remove husks and stones from wheat.
2. To separate two or more useful components from the mixture for their individual use. An example is churning curd to get useful components like butter and buttermilk.
3. To obtain a substance in its pure form. For example, washing foodstuffs like mustard, sesame, and moong with water to remove the water and purify the necessary substances.
4. To determine the proportion of components in a mixture. When a substance has been adulterated with another substance, we can separate the components other than the original and find out the extent of adulteration.
In simple words: We split mixtures to remove bad parts, get useful parts, make things pure, or see if something is mixed in. For example, we take out stones from wheat, or make butter from curd.

Exam Tip: When answering "why do we separate mixtures," always provide at least two clear reasons and support them with practical, everyday examples to score full marks.

Question 2. ઊપણવું એટલે શું? તે ક્યારે વપરાય છે?
Answer: Winnowing is a method used to separate lighter husks or other light waste mixed with heavier grains or pulses. This process helps remove unwanted substances from food grains.
**Usage:** Farmers use this method to remove husks, dust, or other debris from wheat, millet, or pulses with the help of wind. This technique is useful when one essential component in a mixture of solids is heavy, and the other unwanted components are light enough to be carried away by the wind, allowing for their separation.
In simple words: Winnowing means using wind to separate light stuff, like husks, from heavy grains. Farmers use it to clean wheat and other crops.

Exam Tip: Clearly define "winnowing" and provide a practical example of its application, especially mentioning the role of wind, for a complete answer.

Question 3. રસોઈ કરતાં પહેલાં કઠોળમાંથી ફોતરાં તથા રજકણોને તમે કઈ ' રીતે દૂર કરશો?
Answer: Before cooking, pulses are washed with water. Husks and dust particles are lighter, so they float on the water's surface. When the water is drained, these husks and dust particles are also removed. Washing the pulses two or three times with water in this manner removes impurities. The purified pulses can then be used for cooking.
In simple words: Before cooking, we wash pulses with water. The light husks and dust float and are rinsed away with the water, making the pulses clean for use.

Exam Tip: Focus on the difference in density between the pulses and impurities, and explain how water helps in their separation through floating and draining.

Question 4. ચાળવું એટલે શું? તે ક્યારે વપરાય છે?
Answer: Sieving is a method used to separate components of a mixture that have different sizes using a sieve. This method is applied when components of varying sizes need to be separated.
**Usage:**
1. When grinding grains at a mill, it's essential to remove husks and stones before milling wheat. For this, a large quantity of wheat is poured onto a slanted sieve. This helps remove stones, small pebbles, and other impurities from the wheat, resulting in clean, separated wheat.
2. At construction sites, sieves are used to remove pebbles and small stones from sand.
In simple words: Sieving uses a sieve to separate big and small things in a mixture. It's used to clean grains at flour mills or sand at building sites.

Exam Tip: Remember to define sieving based on particle size differences and give at least one common application to illustrate its use effectively.

Question 5. રેતી અને પાણીના મિશ્રણને તમે કઈ રીતે અલગ કરશો?
Answer: To separate a mixture of sand and water, we would use a combination of sedimentation and decantation methods.
First, let the mixture settle in a glass for some time. The sand will sink to the bottom of the glass. This process is called sedimentation. Then, carefully tilt the glass and pour the water from the top into another beaker. This process is called decantation. In this way, sand and water can be separated from the mixture. (Also, filtration can further separate sand and water from the mixture if finer particles remain suspended).
In simple words: To separate sand and water, first let the sand sink to the bottom (sedimentation). Then, carefully pour off the water (decantation).

Exam Tip: For separating immiscible liquid-solid mixtures, always mention both sedimentation (settling) and decantation (pouring off) as a combined process for clarity.

Question 6. ઘઉંના લોટમાં મિશ્ર થયેલી ખાંડને તમે અલગ કરી શકો? જો હા, તો કઈ રીતે કરશો?
Answer: Yes, sugar mixed with wheat flour can be separated by sieving. Since sugar particles are generally larger than wheat flour particles, the mixture can be sieved using a flour sieve. This will cause the sugar particles to remain on top of the sieve, while the flour will pass through into the container below. This way, sugar can be separated from the mixture.
In simple words: Yes, you can separate sugar from wheat flour by sieving. The sugar grains are bigger, so they will stay on the sieve while the flour goes through.

Exam Tip: The key to separating solid mixtures by sieving is a noticeable difference in particle size. Always explain this size difference in your answer.

Question 7. ડહોળા પાણીના નમૂનામાંથી ચોખ્ખું પાણી કઈ રીતે મેળવશો?
Answer: To obtain clean water from a sample of turbid water, methods of sedimentation, decantation, and filtration are used.
• First, let the turbid water in a glass stand undisturbed for about an hour. This will cause dirt, soil, and sand particles to settle at the bottom of the glass.
• Then, gently pour the clear water from the top into another beaker through decantation. The beaker will contain almost clear water.
• Subsequently, take the decanted water and filter it through a filter paper in a beaker. The water obtained in this beaker will be completely clean.
In simple words: To get clean water from muddy water, first let the mud settle (sedimentation). Then, pour off the top clear water (decantation). Finally, pass it through a filter paper (filtration) to make it completely clean.

Exam Tip: For purifying turbid water, remember to explain the sequence of all three steps: sedimentation for heavier particles, decantation for the liquid layer, and filtration for finer suspended impurities.

Question 8. ખાલી જગ્યા પૂરોઃ

Question 8.1. ચોખાના દાણાને ગૂંડાથી અલગ કરવાની પદ્ધતિને એ ઊપણવું કહે છે.
Answer:
(i) ચોખાના દાણાને ગૂંડાથી અલગ કરવાની પદ્ધતિને એ ઊપણવું કહે છે.
In simple words: Separating rice grains from husks is called winnowing.

Exam Tip: Remember that winnowing is specifically used to separate lighter husks from heavier grains using wind.

Question 8.2. જ્યારે ગરમ કરીને ઠંડા કરેલા દૂધને કાપડના ટુકડા પર રેડવામાં આવે છે, ત્યારે કાપડના ટુકડા પર મલાઈ રહી જાય છે. મલાઈથી દૂધને અલગ કરવાની આ રીતને ગાળણક્રિયા કહે છે.
Answer:
(ii) જ્યારે ગરમ કરીને ઠંડા કરેલા દૂધને કાપડના ટુકડા પર રેડવામાં આવે છે, ત્યારે કાપડના ટુકડા પર મલાઈ રહી જાય છે. મલાઈથી દૂધને અલગ કરવાની આ રીતને ગાળણક્રિયા કહે છે.
In simple words: When cooled milk is poured through a cloth, the cream stays on the cloth. This separation is called filtration.

Exam Tip: Filtration separates substances based on particle size, where smaller liquid particles pass through, and larger solid particles (like cream here) are retained.

Question 8.3. દરિયાના પાણીમાંથી મીઠું બાષ્પીભવન પદ્ધતિથી મેળવવામાં આવે છે.
Answer:
(iii) દરિયાના પાણીમાંથી મીઠું બાષ્પીભવન પદ્ધતિથી મેળવવામાં આવે છે.
In simple words: Salt is taken out of seawater by evaporation.

Exam Tip: Evaporation is used to separate a soluble solid from its liquid solvent, as the liquid turns into vapor, leaving the solid behind.

Question 8.4. જ્યારે ડહોળા પાણીને વાસણમાં આખી રાત રહેવા દેવામાં આવે છે ત્યારે અશુદ્ધિઓ તળિયે બેસી જાય છે. ચોખ્ખું પાણી પછી ઉપરથી કાઢી લેવામાં આવે છે. આ ઉદાહરણમાં અલગીકરણની નિતારણ પદ્ધતિ ઉપયોગમાં લેવાઈ છે.
Answer:
(iv) જ્યારે ડહોળા પાણીને વાસણમાં આખી રાત રહેવા દેવામાં આવે છે ત્યારે અશુદ્ધિઓ તળિયે બેસી જાય છે. ચોખ્ખું પાણી પછી ઉપરથી કાઢી લેવામાં આવે છે. આ ઉદાહરણમાં અલગીકરણની નિતારણ પદ્ધતિ ઉપયોગમાં લેવાઈ છે.
In simple words: Letting muddy water settle overnight and then carefully pouring off the clear water above is an example of decantation.

Exam Tip: Decantation involves separating a liquid from settled solids by gently pouring it out without disturbing the settled material.

Question 9. ખરું કે ખોટું?

Question 9.1. પાણી અને દૂધના મિશ્રણને ગાળણ વડે અલગ કરવામાં આવું છે.
Answer: ખોટું
In simple words: The statement that water and milk mixtures are separated by filtration is false.

Exam Tip: Filtration separates insoluble solids from liquids. Water and milk form a miscible mixture and cannot be separated by simple filtration.

Question 9.2. દળેલું મીઠું અને ખાંડના મિશ્રણને ઊપણવાની ક્રિયા વડે અલગ કરી શકાય છે.
Answer: ખોટું
In simple words: The statement that powdered salt and sugar can be separated by winnowing is false.

Exam Tip: Winnowing relies on differences in weight and requires air currents. Powdered salt and sugar have similar densities and particle sizes, making winnowing ineffective.

Question 9.3. ગાળણ વડે ખાંડ અલગ કરી શકાય છે.
Answer: ખોટું
In simple words: The statement that sugar can be separated by filtration is false.

Exam Tip: Sugar dissolves in water, forming a solution. Filtration can only separate insoluble substances, not dissolved ones.

Question 9.4. અનાજ અને ફોતરાં નિતારવાની પદ્ધતિ વડે અલગ કરી શકાય છે.
Answer: ખોટું
In simple words: The statement that grains and husks can be separated by decantation is false.

Exam Tip: Decantation is for separating a liquid from settled solids. Grains and husks are both solids and are better separated by winnowing or sieving based on size/weight differences.

Question 10. લીંબુના રસ અને ખાંડને પાણીમાં મિશ્રણ કરવાથી લીંબુ શરબત બને છે. તેને ઠંડું કરવા માટે તમે તેમાં બરફ ઉમેરો છો. તમારે શરબતમાં ખાંડ ઓગાળ્યા પછી બરફ ઉમેરવો જોઈએ કે પહેલાં? કઈ પરિસ્થિતિમાં વધુ ખાંડ ઓગાળવી શક્ય બનશે?
Answer: We should add ice after the sugar has dissolved in the lemon water. The ability of sugar to dissolve in water decreases at lower temperatures. Therefore, to dissolve more sugar, it should be added to water before the water cools down. Once the sugar has completely dissolved, ice should be added to chill the lemon sherbet.
In simple words: You should add ice after the sugar has dissolved in the lemon water. Sugar dissolves better in warm water, so dissolve it first, then add ice to cool it down.

Exam Tip: Solubility of solids generally increases with temperature. Always dissolve solids in warm or room temperature liquids before cooling for maximum dissolution.

Textbook Activities

Activity 1:

Understanding the method, purpose, and application of separation.

Procedure: Column 1 of Table 5.1 lists some methods of separation. The purpose of separation and the use of separated components are shown in columns 2 and 3, respectively. However, the information in columns 2 and 3 is scrambled. Match the method with its purpose and the use of the separated components correctly.

Table 5.1 Why do we separate substances?

Activity 2:

Understanding the "handpicking" method of separation.

Materials: Bag of grains, paper.

Procedure:
1. Bring a bag of grains purchased from the market.
2. Spread the grains on a paper.
3. Handpick and remove stones, husks, broken grains, and other grain types. Clean all the grains in this way.

Observation: Stones, husks, and other particles can be removed from the grains by handpicking.

Conclusion: Unwanted particles can be separated from grains using the "handpicking" method.

Activity 3:

Understanding the winnowing method of separation.

Materials: Sand, sawdust, dry leaves, dish.

Procedure:
1. Mix sand with sawdust and crushed dry leaves.
2. Take this mixture in a dish.
3. Go to an open ground and stand on a raised platform.
4. Hold the dish containing the mixture at shoulder height.
5. Tilt the dish slightly and allow the mixture to fall slowly when the wind blows. Observe what happens.

Observation: Sand falls directly downwards from the dish, while sawdust and dry leaves are carried away by the wind.

Conclusion: The winnowing method separates heavier components from lighter components in a mixture.

Activity 4:

Removing impurities from flour by sieving.

Materials: Wheat flour, bowl, sieve, chalk powder, plate.

Procedure:
1. Put wheat flour in a bowl.
2. Place a plate below the sieve.
3. Keep shaking the sieve and let the sieved flour fall into the plate. After sieving the flour, observe what remains in the sieve.
4. Mix chalk powder with flour and sieve it. Observe what remains in the sieve.

Observation:
1. Impurities like husks present in the flour remain on the sieve, and the pure flour falls separately into the plate.
2. When chalk powder is mixed with flour and sieved, both the flour and chalk powder pass through the sieve, and nothing remains on the sieve.

Conclusion:
1. Flour particles are smaller than the sieve holes, and bran particles are larger. In this situation, components can be separated by sieving.
2. Flour and chalk powder are almost similar in size and both are smaller than the sieve holes, so they cannot be separated.

Activity 5:

Obtaining clean water by decantation and filtration processes from turbid water.

Materials: A glass filled with turbid water, two empty beakers, a funnel, filter paper, stand.

Figure: Sedimentation and Decantation.

Procedure:
1. Allow the glass containing turbid water to stand still for about an hour (without shaking).
2. After an hour, observe that dirt, soil, and sand will settle at the bottom. (See Figure (i)).
3. Carefully tilt the glass without disturbing the dirt, soil, and sand, and collect the clear water in a beaker.
4. In this way, most of the water is decanted into the beaker. (See Figure (ii)).

5. Now, set up a funnel on a stand as shown in Figure (iii) and place a folded filter paper inside the funnel.
6. Place another empty beaker below the funnel. Wet the filter paper.
7. Slowly pour the decanted water into the funnel. (Be careful not to tear the filter paper).
8. Observe the filtered water in the beaker.

Observation: Impurities floating in the decanted water are visible. Subsequently, the water obtained through filtration is cleaner.

Conclusion:
1. Insoluble and heavier impurities in water settle down through the process of sedimentation.
2. Afterwards, insoluble and heavier impurities in water can be partially removed by decantation.
3. Heavy as well as light insoluble impurities in water can be removed by filtration.

Activity 6:

Understanding the evaporation method.

Materials: Beaker, water, salt, wire gauze, Bunsen burner.

Figure: Evaporation and Condensation.

Procedure:
1. Take some water in a beaker and heat it on a Bunsen burner as shown in the figure.
2. When all the water evaporates and escapes as vapor, observe if any residue remains in the beaker.
3. Now take some water in a beaker and dissolve salt in it. The salt solution will appear clear.
4. Gently heat the beaker containing the salt solution.

5. Check if any residue remains in the beaker after all the water evaporates through the process of evaporation.
Observation: A white residue is found in the beaker. This residue is salt.

Conclusion: Salt can be obtained from a salt solution by the method of evaporation.

Activity 7:

Separating components from a mixture of sand and salt.

Materials: Mixture of sand and salt, water, glass, three beakers, funnel, kettle, metal plate, ice, gas stove.

Procedure:
1. Take the mixture of sand and salt in a beaker and add some water to it.
2. Let the beaker stand for some time. This will cause the sand to settle at the bottom of the beaker, and the salt will dissolve in the water.
3. Carefully tilt the beaker gently and collect the clear water in a glass. Wet sand will remain in the beaker.
4. Filter the decanted water with the help of filter paper and a funnel into a beaker.
5. The filtered water will contain salt in dissolved form. Salt and water need to be separated from this.
6. Pour the filtered liquid into a kettle and close its lid.
7. Heat the kettle. Let the liquid inside boil.
8. Take some ice on a metal plate.
9. Hold the plate with ice slightly above the spout of the kettle. This will cause the steam escaping from the kettle to cool down and turn into water. Collect this water in a beaker. Taste it.
10. What remains in the kettle after all the water has evaporated?

Observation:
1. Salt remains in the kettle.
2. Pure water without taste is obtained in the beaker placed under the icy plate.

Conclusion: Components can be separated from a mixture of sand and salt through the processes of decantation, filtration, evaporation, and condensation.

Activity 8:

Making a saturated solution of salt.

Materials: Beaker, salt, water, spoon.

Procedure:
1. Take half a cup of water in a beaker.
2. Add a spoonful of salt to the beaker and stir until it dissolves completely.
3. Again, add a spoonful of salt and stir well.
4. Keep adding a spoonful of salt each time and stirring.
5. When the salt stops dissolving and settles at the bottom, stop adding salt.
6. Filter the solution in the beaker. This solution is a saturated solution of salt.

Activity 9:

More salt can be dissolved in a saturated solution by heating it.

Materials: Beaker, salt, water, gas stove.

Procedure:
1. Take some water in a beaker and keep dissolving salt until no more salt dissolves.
2. Filter this solution to remove excess salt. The resulting solution is a saturated solution of salt.
3. Now, add a little more salt to the saturated salt solution. This added salt will settle without dissolving in the solution.
4. Now, heat the solution. After some time, observe what happens to the undissolved salt at the bottom of the beaker.
5. Let this hot solution cool down. Does the salt reappear at the bottom of the beaker?

Observation: The undissolved salt in the saturated solution dissolves when the solution is heated.

Conclusion: More salt can be dissolved in a saturated solution by heating it.

Activity 10:

To prove that water dissolves different substances in different amounts.

Materials: Two beakers, water, salt, sugar, alum.

Procedure:
1. Take equal amounts of half a cup of water in both beakers.
2. Add one spoonful of salt to one beaker and stir until it dissolves.
3. Keep adding one spoonful of salt to the beaker until the solution becomes saturated.
4. Note how many spoonfuls of salt were added to the beaker when the solution became saturated in Table 5.2.
5. Now, repeat this activity for sugar and alum. Note how many spoonfuls of sugar and alum were needed in Table 5.2.

Table 5.2 Required amount of solvent in saturated solutions of different substances:

Observation: Different soluble substances have different maximum dissolving capacities in the same amount of water.

Conclusion: Water dissolves different substances in different amounts.