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Introduction

Olympiad Notes: Separation of Substance | Science Olympiad Class 6

  • Commonly, substances are separated or purified through various processes in everyday tasks. For instance, when making tea, we filter tea powder, and before cooking, rice is often cleaned with water.
  • These processes of separation are widely utilized in our routines to ensure the purification and isolation of different substances.
  • Throughout this chapter, we will delve into studying several methods employed for separating substances effectively.

Question for Olympiad Notes: Separation of Substance
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What is the process commonly used to filter tea powder?
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Handpicking

  • Handpicking involves the manual separation of stones, dust, husk from grains such as rice and wheat.
  • Advantages include its effectiveness in eliminating larger particles of dust from smaller grains.
  • However, handpicking is disadvantaged by its time-consuming nature.
  • It is not suitable for removing small-sized dust and stone particles efficiently.

Threshing

  • Grain stalks undergo sun-drying as a preliminary step.
  • Post drying, the stalks are manually beaten vigorously to separate the grains from the stalks, a process known as threshing.
  • Occasionally, bullocks or machinery are employed for this purpose.

Question for Olympiad Notes: Separation of Substance
Try yourself:
What is the process of separating grains from stalks called?
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Winnowing

  • A prevalent method used for separating heavier grain particles from lighter dust particles involves a specific technique.
  • The mixture, comprising both grain and dust, is elevated to a considerable height, roughly around shoulder or chest level.
  • By tilting the mixture slightly and providing a gentle movement, lighter particles such as husk are encouraged to fall out.
  • This process is commonly referred to as threshing and is effective in segregating the desired grains from the unwanted lighter particles.

Sieving

  • Sieves serve the purpose of filtering out dust particles and are frequently employed in the cleaning of flour.
  • This method involves the use of a sieve where fine flour particles pass through the sieve's holes while larger impurities are retained on the sieve.
  • Sieving effectively separates finer components from larger impurities, making it a common technique for refining flour.

Sedimentation and Decantation


  • Despite previous cleaning processes, residual small particles might remain in purchased rice.
  • To address this, rice is washed with water just before cooking, leveraging a separation method.
  • Sedimentation occurs as heavier rice particles settle down in the water due to their weight.
  • Decantation, a process of separation, involves discarding the water along with lighter dust particles after they float, leaving behind the settled heavier rice particles.
  • Similarly, oil and water are separated using a comparable method: water settles as it is heavier than oil, allowing the oil to be separated from the top layer.

Filtration

  • Filtration is a separation technique akin to the use of a tea filter, commonly employed to separate substances.
  • This process involves passing a liquid containing solid particles through a filter or filter paper, effectively separating the solids from the liquid.
  • Fruit and vegetable juices are often subjected to filtration for refining purposes using a similar method.
  • Certain substances can also undergo filtration using filter paper, extending the applicability of this separation process.

Evaporation

  • The procedure to separate salt from water (seawater) involves heating the water until it completely transforms into vapor, leaving the salt residue behind.
  • This transformation of a liquid into its vapor form is termed as evaporation.
  • Evaporation serves as the method through which salt is separated from seawater, as the water vaporizes, leaving the salt behind in its solid form.

Question for Olympiad Notes: Separation of Substance
Try yourself:
What method is used to separate heavier grain particles from lighter dust particles?
View Solution

Salt-Sand mixture


  • In scenarios involving mixtures like sand and salt, multiple methods may be necessary for separation.
  • Mixing the sand and salt mixture with water initiates a process where salt dissolves in water while the sand remains insoluble.
  • Following this, sedimentation occurs as the heavier sand particles settle to the bottom.
  • Decantation is then employed, allowing the pouring out of the water mixture containing dissolved salt, while the settled sand remains unaffected.
  • Heating the water to induce evaporation separates the salt from the water, leaving the salt behind in the container.
  • Cooling down the water vapor using an ice-cold plate initiates condensation, transforming the vapor back into liquid water, which can be collected in a separate container.
  • By employing these sequential processes – sedimentation, decantation, evaporation, and condensation – the sand and salt are effectively separated from each other and from the water.

Saturated Solution

  • When a solute is added to a solvent, initially, it dissolves into the liquid.
  • However, upon continuously adding more solute, a point is reached where the solute no longer dissolves. This indicates that the solvent has reached its 'Saturating point', and further solute cannot be dissolved.
  • The saturation point of a solvent is influenced by several factors:
    • Temperature of the solvent
    • Pressure of the solvent
    • Nature of both the solvent and solute
  • Understanding the saturation point is crucial as it determines the maximum amount of solute that can be dissolved in a given amount of solvent under specific conditions.
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FAQs on Olympiad Notes: Separation of Substance - Science Olympiad Class 6

1. What is the process of handpicking?
Ans. Handpicking is a method of separating substances by manually picking out the desired material from a mixture. It is usually done when the substances in the mixture have distinct physical properties that make them easily identifiable and separable by hand.
2. How does the process of filtration work?
Ans. Filtration is a process of separating solid particles from a liquid or gas by passing the mixture through a filter medium. The filter medium has pores that allow the liquid or gas to pass through while trapping the solid particles. Gravity, vacuum, or pressure can be used to facilitate the filtration process.
3. What is the purpose of evaporation in the separation of substances?
Ans. Evaporation is a process used to separate a soluble solid from a liquid by heating the mixture. The liquid evaporates, leaving behind the solid residue. This method is commonly used to separate salt from saltwater, as the water evaporates, leaving the salt crystals behind.
4. How is sieving different from filtration?
Ans. Sieving and filtration are both methods of separating substances, but they differ in their mechanism. Sieving involves passing a mixture through a sieve or mesh to separate larger particles from smaller ones. It is mainly used for separating solid particles of different sizes. Filtration, on the other hand, involves the use of a filter medium to separate solid particles from a liquid or gas based on their size or solubility.
5. What is sedimentation and decantation?
Ans. Sedimentation is the process by which solid particles settle down at the bottom of a container due to gravity. Decantation is the method of pouring off the liquid portion of a mixture, leaving the settled solids behind. This process is commonly used to separate a mixture of solid and liquid components where the solid particles are denser and settle down over time.
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