Class 6 Science Chapter 3 Important Question Answers - Separation of Substances

Very Short Answer Type Questions

Q1: What is a mixture?
Ans: A mixture is a substance composed of two or more substances, where each component retains its unique properties.

Q2: Give an example of a pure substance.
Ans: Distilled water is an example of a pure substance.

Q3: What is the main reason for the separation of substances?
Ans: The main reason for the separation of substances is to take out useful substances from a mixture.

Q4: What method is used to separate pebbles from rice?
Ans: Handpicking.

Q5: How is threshing done manually?
Ans: Small bundles of harvested stalks are thrashed on a hard surface to separate the grains.

Q6: What method is used to separate bran from flour?
Ans: Sieving.

Q7: Define winnowing.
Ans: Winnowing is the process of separating lighter particles from heavier particles with the help of wind.

Q8: What is the purpose of a combine harvester in farming?
Ans: A combine harvester is used to harvest, thresh, and winnow in a single operation.

Q9: What is sedimentation?
Ans: Sedimentation is the process where insoluble particles settle down at the bottom of a mixture.

Q10: How is salt separated from a solution of salt and water?
Ans: Salt is separated by using evaporation and condensation.

Short Answer Type Questions

Q11: Explain the process of handpicking as a method of separation.
Ans: Handpicking is a simple method of separation used when unwanted material in a mixture is in small quantity and has different characteristics (shape, size, or color) from the useful materials. For example, pebbles, broken grains, and insects can be separated from rice, wheat, and pulses by handpicking.

Q12: Describe how sieving is used to separate substances.
Ans: Sieving is employed when the particle size is too small to be picked by hand or when the quantity is large. A sieve with appropriate-sized holes is used to separate substances. Larger particles are retained by the sieve, while smaller ones pass through. For example, sieving can be used to separate bran from flour.

Q13: Explain the process of winnowing for separating grain from husk.
Ans: Winnowing involves using wind to separate lighter particles (husk) from heavier particles (grain). Farmers drop the mixture of wheat and husk from a height. The husk is carried away by the wind, forming a heap at a distance, while the heavier wheat grains fall vertically to form a separate heap.

Q14: How do sedimentation, decantation, and filtration work together to separate substances?
Ans: Sedimentation involves allowing insoluble particles to settle down at the bottom. Decantation is the process of pouring out the upper layer (liquid) from the container, leaving the sediment behind. Filtration is used to separate fine insoluble solid particles from the liquid. These methods are often used in combination to separate soluble and insoluble solids from a mixture of solids and liquids.

Q15: Describe how salt is separated from sea water using evaporation and condensation.
Ans: Sea water is collected in shallow pits and allowed to evaporate. As the water evaporates, crystals of salt are obtained in the pits. The salt is then sent to factories for further purification. Condensation is the process of converting water vapor back into liquid, which is not directly involved in this separation.

Long Answer Type Questions

Q16: Explain the process of threshing in detail and mention its traditional and modern methods.
Ans: Threshing is the process of separating seeds from harvested stalks. In manual threshing, small bundles of harvested stalks are thrashed on a hard surface to separate the grains. Traditional threshing with animals involves spreading stalks around a pole and using bullocks to walk over them, trampling to separate grains. Modern methods use threshing machines powered by diesel engines or electric motors, saving time and labor.

Q17: Describe the working principle of a combine harvester and its significance in modern farming.
Ans: A combine harvester is a machine that performs harvesting, threshing, and winnowing in a single operation. It significantly reduces the labor and time required for these tasks. In modern farming, combine harvesters are crucial, as they increase efficiency and productivity, especially in large-scale farming operations. For example, they are commonly used in developed countries like the USA and are also seen in farms in India, particularly in Punjab.

Q18: Discuss the applications of evaporation and condensation in separating a soluble solid from water.
Ans: Evaporation is the process of converting water into vapor, while condensation is the process of converting water vapor into liquid. Together, these processes can be used to separate a soluble solid from water. For instance, salt can be separated from a saltwater solution by collecting the water in shallow pits and allowing it to evaporate. As the water evaporates, salt crystals are obtained. These crystals can be further purified in factories.

Q19: Explain the concept of a saturated solution and an unsaturated solution with examples.
Ans: A saturated solution is one in which a given quantity of a solvent (usually water) has dissolved as much solute (solid) as it can at a specific temperature. No more solute can be dissolved in the solution at that temperature. An unsaturated solution, on the other hand, can dissolve more solute. For example, a glass of water with sugar dissolved in it until no more sugar can dissolve is a saturated solution. If you add more sugar and it dissolves, it becomes an unsaturated solution.

Q20: Discuss the role of separation methods in our daily lives and give examples.
Ans: Separation methods play a crucial role in our daily lives. For example, filtration is used in purifying drinking water, winnowing is used in agriculture to separate grain from husk, and sieving is used in baking to separate fine flour from bran. Separation methods are also used in industries for various purposes, such as separating different-sized particles and purifying chemicals. Overall, these methods are essential for obtaining pure substances and useful components from mixtures.