Class 6 Science Chapter 3 Case Based Questions - Separation of Substances

Case 1: Separation of Substances in Agriculture

Mr. Patel is a farmer in India, and he's been using traditional methods for separating grains from harvested stalks. He's curious about modern farming equipment. Answer the following questions:

Q1: Explain the traditional method Mr. Patel uses for threshing. What are the advantages and disadvantages of this method?
Ans: Mr. Patel uses manual threshing, where small bundles of harvested stalks are thrashed on a hard surface to separate the grains. The advantage is that it's simple and doesn't require machinery. The disadvantage is that it's labor-intensive.

Q2: Describe the modern farming equipment called a combine harvester. How does it work, and what are its benefits over traditional methods?
Ans: A combine harvester is a modern farming machine that can harvest, thresh, and winnow in a single operation. It works by cutting and collecting crops, separating grains from stalks, and removing husks. Benefits include increased efficiency and reduced labor.

Q3: What is the main purpose of threshing in agriculture?
(a) Separating grains from harvested stalks
(b) Separating stones from rice
(c) Separating sand from gravel
(d) Separating bran from flour
Ans: (a)

Q4: What is the purpose of winnowing in agriculture?
(a) Separating grains from husk
(b) Separating stones from rice
(c) Separating sand from gravel
(d) Separating bran from flour
Ans: (a)

Case 2: Separation of Substances in Filtration

Sophia is a chemistry student conducting an experiment to separate fine insoluble solid particles from a liquid. Answer the following questions:

Q5: Explain the process of filtration that Sophia is using in her experiment. What equipment does she need, and how does it work?
Ans: Filtration is a process where a mixture is passed through a filter paper or sieve to separate solid particles from the liquid. Sophia needs a funnel, filter paper, and a container. The liquid passes through the filter paper, leaving solid particles behind.

Q6: What are the common applications of filtration in daily life? Provide at least three examples.
Ans: Common applications of filtration include purifying drinking water, filtering coffee grounds, and separating impurities from cooking oil.

Q7: What does filtration help separate?
(a) Soluble solids from liquids
(b) Insoluble solids from liquids
(c) Gases from liquids
(d) Liquids from solids
Ans: (b)

Q8: In which of the following scenarios would filtration be most suitable?
(a) Separating sugar from tea
(b) Separating salt from water
(c) Separating oxygen from air
(d) Separating oil from vinegar
Ans: (a)

Case 3: Separation of Substances in Evaporation and Condensation

Lisa wants to separate salt from a solution of salt and water. She decides to use evaporation and condensation. Answer the following questions:

Q9: Explain how Lisa can separate salt from the saltwater solution using evaporation and condensation. What are the steps involved?
Ans: Lisa can separate salt from the saltwater solution by evaporating the water, leaving behind salt crystals. Then, she can use condensation to collect the evaporated water vapor and convert it back into liquid water.

Q10: Why is it important to use both evaporation and condensation in this process?
Ans: Using both evaporation and condensation ensures that only the water is separated from the solution, leaving the salt behind.

Q11: What is a saturated solution?
(a) A solution with too much solid dissolved in it
(b) A solution with too little solid dissolved in it
(c) A solution with an equal amount of solid and liquid
(d) A solution with no solid dissolved in it
Ans: (a)

Q12: What is the purpose of condensation in the separation of salt from a saltwater solution?
(a) To convert liquid water into vapor
(b) To convert water vapor into liquid water
(c) To separate salt from water
(d) To dissolve salt in water
Ans: (b)

Case 4: Separation of Substances in Handpicking and Sieving

John is helping his mother in the kitchen, and she asks him to separate stones from a bowl of rice. Answer the following questions:

Q13: Describe how John can use handpicking to separate stones from rice. What conditions make handpicking suitable for this task?
Ans: John can use handpicking to separate stones from rice because the stones have different sizes and colors than the rice. He can simply pick out the stones by hand.

Q14: Explain the process of sieving and how it can be used to separate substances. What type of materials can be separated effectively through sieving?
Ans: Sieving involves using a sieve with appropriately sized holes to separate substances. It is effective for separating materials like bran from flour, sand from gravel, and pearls of different sizes.

Q15: What is the primary condition that makes handpicking effective for separating substances?
(a) Differences in size and color
(b) Differences in taste
(c) Differences in temperature
(d) Differences in shape and smell
Ans: (a)

Q16: What can be effectively separated using sieving?
(a) Salt from water
(b) Bran from flour
(c) Air from gases
(d) Liquid from solids
Ans: (d)

Case 5: Separation of Substances in Sedimentation and Decantation

Sara is conducting an experiment with muddy water. She wants to separate soil and sand from the water. Answer the following questions:

Q17: Explain the process of sedimentation and how it can be used to separate soil and sand from muddy water. What happens during sedimentation?
Ans: Sedimentation involves allowing insoluble particles (soil and sand) to settle at the bottom of the container over time. Sara can use this process to separate soil and sand from muddy water.

Q18: What is the purpose of decantation, and when is it used in conjunction with sedimentation?
Ans: Decantation is used after sedimentation to carefully pour out the upper layer (water) while leaving the sediment (soil and sand) behind.

Q19: What is the outcome of sedimentation in the separation of soil and sand from water?
(a) Soil and sand remain suspended in water.
(b) Soil and sand settle at the bottom of the container.
(c) Water evaporates completely.
(d) Soil and sand turn into gas.
Ans: (b)

Q20: When is decantation typically used in the separation of substances?
(a) Before sedimentation
(b) After sedimentation
(c) Instead of sedimentation
(d) During filtration
Ans: (b)