All questions of Separation of Substances for Class 6 Exam

This method of separating components of a mixture is calledwinnowing. Winnowing is used to separate heavier and lighter components of a mixture by wind or by blowing air. threshing is done with the help of bullocks. Ans is B

If saturated solution is heated the solution become unsaturated because solubility is directly depends upon temperature, so on heating solubility of the solution increase and its become unsaturated or in other words the solution is now capable to take some more solute into it.

The maximum amount of solute dissolved in solvent at any concentration is called Saturated solutions.in these solutions ,there is no solute can be added after the completion of the reaction.

Sieving is used when the particles are too small to be separated by hand and the quantity is large.

You should add ice after dissolving the sugar to dissolve more sugar in lemonade. When sugar is dissolved in warm water, it dissolves more readily due to higher solubility at warmer temperatures. Adding ice before dissolving sugar can reduce the temperature of the mixture, making it harder for the sugar to dissolve. Therefore, it is best to dissolve the sugar in warm or room-temperature water first and then add ice to cool the lemonade. This approach ensures that the maximum amount of sugar is dissolved.

Sieving is the method used to separate sugar from wheat flour. Since sugar and flour have different particle sizes, a sieve with appropriate mesh can separate them. This method is commonly used in cooking and baking to ensure that flour and sugar are evenly mixed or to remove lumps from the ingredients.

Understanding Evaporation
Evaporation is a key process in the water cycle and involves the transformation of a liquid into a gas. Here’s a detailed breakdown of why the statement is false:
Definition of Evaporation
- Evaporation is the process where molecules at the surface of a liquid gain enough energy to transition into the gaseous state.
- This process occurs at any temperature, as long as the liquid has a surface.
Transition of States
- The correct transition for evaporation is:
- Liquid → Gas
- This means that evaporation cannot be a process where a liquid changes into a solid.
Solidification vs. Evaporation
- When a liquid changes into a solid, the process is called freezing or solidification.
- For example, water turns into ice when it freezes.
Examples of Evaporation
- Common examples include:
- Puddles drying up on a sunny day
- Wet clothes drying in the air
Conclusion
In summary, evaporation is indeed the process of liquid turning into gas, not solid. Therefore, the statement "Evaporation is a process where a liquid changes into a solid" is false. The correct answer is option 'B'. Understanding these processes helps us grasp essential concepts in science and the environment.

Understanding the Process of Purification
When we talk about obtaining clear water from muddy water, we refer to a series of processes aimed at separating impurities. One of the most effective methods involves the use of alum, a chemical compound that helps in this purification process.
What is Loading?
- Loading is the process where alum is added to muddy water.
- The alum causes tiny particles in the muddy water to clump together, forming larger particles called flocs.
- This process enhances sedimentation, where these heavier flocs settle at the bottom of the container, leaving behind clearer water.
Steps Involved in the Process
1. Addition of Alum:
- Alum is dissolved in water and mixed with muddy water.
2. Clumping of Particles:
- The positively charged ions in alum attract the negatively charged particles in the muddy water, causing them to stick together.
3. Formation of Flocs:
- The clumped particles form larger flocs that are easier to remove from the water.
4. Sedimentation:
- Over time, these flocs settle down to the bottom of the container due to gravity.
5. Separation:
- The clear water on top can then be carefully decanted or siphoned off, leaving the sediment behind.
Conclusion
In conclusion, while decantation, filtration, and sedimentation are related processes, the term "loading" specifically refers to the addition of alum to initiate the purification process. This crucial step is what makes the transition from muddy water to clear water possible.

Condensation
Condensation is the process of converting water vapor into its liquid form. This occurs when water vapor in the air comes into contact with a surface or air that is cooler than the dew point temperature of the water vapor. This causes the water vapor to lose heat energy, slow down, and eventually turn into liquid water droplets.

Key Points:
- Condensation is the opposite of evaporation, where liquid water turns into water vapor.
- The formation of dew on grass in the morning is a common example of condensation.
- Condensation is an important part of the water cycle, where water is constantly being circulated between the atmosphere, land, and oceans.
- Cloud formation is also a result of condensation, where water vapor in the air cools and forms visible water droplets or ice crystals.

Understanding the Methods of Separation
In the context of separating mixtures, let's explore the three methods mentioned: Winnowing, Threshing, and Sieving, to determine which does not require air.
1. Winnowing
- Definition: Winnowing is a method used to separate lighter particles from heavier ones, commonly used for grains.
- Air Requirement: This process employs wind or air currents to blow away the lighter chaff, making air essential for its operation.
2. Threshing
- Definition: Threshing is the process of separating grains from the husks and straw.
- Air Requirement: While it can involve mechanical means to beat the grains, it often uses air to help separate the lighter husks from the heavier grains. Thus, air plays a role in this method as well.
3. Sieving
- Definition: Sieving is a simple method of separation that involves passing a mixture through a sieve or mesh to separate particles based on size.
- Air Requirement: This method does NOT rely on air; it purely depends on the size of the particles being separated.
Conclusion
From the explanations:
- Winnowing requires air.
- Threshing also involves air in many cases.
- Sieving is the only method that operates independently of air.
Thus, the correct answer is B) Only Y, Z, as Threshing (Y) and Sieving (Z) can be performed without the need for air, while Winnowing (X) cannot.

Understanding Solutions
In chemistry, solutions can be classified based on their solute concentration. When discussing sugar solutions, it's important to differentiate between unsaturated and saturated solutions.
Unsaturated Solution
- An unsaturated solution is one where the solvent can still dissolve more solute at a given temperature.
- For example, if you have a glass of water with sugar dissolved in it and you can keep adding more sugar without any leftover at the bottom, this solution is unsaturated.
- The temperature remains constant in this scenario, indicating that the solution can accommodate more solute.
Saturated Solution
- A saturated solution occurs when no more solute can dissolve in the solvent at a specific temperature.
- In this case, if you add sugar and it does not dissolve, remaining at the bottom, the solution is saturated.
- The sugar particles are in equilibrium with the dissolved particles, meaning the solution has reached its maximum solute concentration.
Examples of Solutions
- Unsaturated Solution: A glass of warm water to which you can add more sugar easily.
- Saturated Solution: A glass of cold water where sugar starts to settle at the bottom after reaching the maximum dissolving point.
Conclusion
The correct answer to the question is option 'A' because an unsaturated solution allows for additional solute to dissolve without altering the temperature. Understanding these concepts helps in grasping the basic principles of solubility and solutions.

Explanation:

Methods of Separating Substances from Mixtures:

Handpicking:
- Involves manually picking out components of a mixture based on their physical properties.
- Useful for separating larger particles from a mixture.

Winnowing:
- Involves blowing air through a mixture to remove lighter components.
- Effective for separating grains from chaff or dirt.

Sieving:
- Involves passing a mixture through a sieve or mesh to separate particles based on size.
- Useful for separating solids of different sizes.

Sedimentation:
- Involves allowing particles to settle at the bottom of a container due to gravity.
- Useful for separating insoluble solids from liquids.

Decantation:
- Involves pouring off the liquid portion of a mixture while leaving the solid behind.
- Useful for separating liquids with different densities.

Filtration:
- Involves passing a mixture through a filter to separate solid particles from a liquid.
- Useful for separating insoluble solids from liquids.
These methods are essential in chemistry and everyday life for separating different substances from mixtures based on their physical properties.

Understanding Sedimentation
Sedimentation is a natural process used to separate solid particles suspended in a liquid by allowing them to settle down due to gravity. This method is commonly applied in various fields including water treatment, mining, and environmental science.
How Sedimentation Works
- Gravity's Role: When a mixture of solid and liquid is left undisturbed, the denser solid particles gradually settle at the bottom of the container. This occurs because gravity pulls the particles downward.
- Time Factor: The rate at which particles settle depends on their size, shape, and density, as well as the viscosity of the liquid. Larger or denser particles settle faster than smaller or lighter ones.
Applications of Sedimentation
- Water Purification: Sedimentation is an essential step in water treatment processes where impurities and suspended solids are removed, leading to cleaner water.
- Industrial Processes: In mining, sedimentation helps in separating valuable minerals from waste material.
Difference from Other Processes
- Filtration: While filtration also separates solids from liquids, it uses a filter medium to physically block solid particles, whereas sedimentation relies on gravity.
- Decantation: This process follows sedimentation; once solids have settled, the clear liquid can be poured off, leaving the sediment behind.
- Evaporation: Evaporation involves converting liquid into vapor to separate dissolved solids, which is entirely different from the settling mechanism of sedimentation.
In summary, sedimentation is an efficient and straightforward method for separating solid particles from liquids, making it a fundamental concept in both science and practical applications.

Method to Separate Tea Leaves from Prepared Tea
When preparing tea, it is essential to separate the tea leaves from the liquid to enjoy a smooth beverage. The best method for this is filtration.
Understanding Filtration
- Definition: Filtration is a process that uses a barrier to separate solid particles from a liquid or gas.
- Application in Tea Preparation: In tea preparation, a filter (often a tea strainer or a fine mesh sieve) is used to catch the tea leaves while allowing the brewed liquid to pass through.
Why Filtration is the Correct Answer
- Efficiency:
- Filtration effectively separates small tea leaves from the liquid, ensuring that only the brewed tea is served.
- Clarity:
- This method helps achieve a clear liquid, free from unwanted particles, enhancing the drinking experience.
- Ease of Use:
- Using a strainer or filter is quick and practical, making it a convenient choice for most tea drinkers.
Other Methods Explained
- Sedimentation:
- This is the process of allowing heavier particles to settle at the bottom of a liquid. It is not effective for tea leaves, which do not settle quickly.
- Decantation:
- This involves pouring off the liquid from a settled solid. It is less precise since some leaves might still be mixed with the liquid.
- Winnowing:
- This method is used for separating grain from chaff, not applicable to tea leaves.
By using filtration, tea drinkers can enjoy their beverage free from any solid remnants, making it the most suitable method for separating tea leaves from prepared tea.

Understanding Immiscible Liquids
Immiscible liquids are those that do not mix together, such as oil and water. When trying to separate these liquids, specific methods are required to achieve effective separation.
Why Use a Separating Funnel?
A separating funnel is the most efficient tool for separating immiscible liquids. Here’s how it works:
- Design: The funnel has a wide body and a narrow neck, allowing for easy separation of layers.
- Density Difference: Immiscible liquids typically have different densities. For example, oil is less dense than water and will float on top.
- Separation Process:
- Pour the mixture into the separating funnel.
- Allow the liquids to settle into distinct layers.
- Open the stopcock at the bottom to let the denser liquid (usually water) drain out, leaving the lighter liquid (like oil) in the funnel.
Other Methods Explained
- Filtration: This method is used to separate solids from liquids or gases. It is not suitable for immiscible liquids.
- Decantation: This involves pouring off one liquid from another after settling, but a separating funnel provides more precision, especially with smaller volumes.
- Evaporation: This technique is used to separate a soluble solid from a liquid, not for immiscible liquids.
Conclusion
The separating funnel is specifically designed for separating immiscible liquids due to its unique structure and functionality, making it the best choice among the options provided.

Introduction:
Mixtures are combinations of two or more substances that are physically mixed together but can be separated through various methods. The need to separate mixtures arises due to several reasons, including the removal of undesirable substances, obtaining desirable substances, and obtaining highly pure substances. Consequently, the correct answer to the given question is option 'D', which encompasses all of the above reasons.

Explanation:
1. Removal of Undesirable Substances:
One of the primary reasons for separating mixtures is to remove undesirable substances. In many cases, mixtures contain impurities or unwanted components that need to be eliminated in order to obtain a desired product or to make the mixture safe for consumption. Separation techniques such as filtration, distillation, and chromatography are commonly employed for this purpose.

- Filtration: Filtration is used to separate a solid-liquid mixture, where the solid particles are larger than the pores of the filter paper or mesh, allowing only the liquid to pass through.
- Distillation: Distillation is used to separate a mixture of two or more liquids with different boiling points. The mixture is heated, and the component with the lower boiling point vaporizes first and can be collected separately.
- Chromatography: Chromatography is a technique that is used to separate a mixture into its individual components based on their different affinities to a mobile phase and a stationary phase.

2. Obtaining Desirable Substances:
Separating mixtures is also essential for obtaining desirable substances. Sometimes, mixtures contain valuable or useful substances that need to be isolated for further processing or utilization. By employing suitable separation methods, these substances can be obtained in their pure form.

- Evaporation: Evaporation is used to separate a mixture of a solid dissolved in a liquid. The mixture is heated, and the liquid component evaporates, leaving behind the solid residue.
- Crystallization: Crystallization is a technique used to separate a solid dissolved in a liquid by cooling the mixture. The dissolved solid forms crystals, which can be separated from the liquid.
- Sublimation: Sublimation is the process of separating a mixture where one component undergoes sublimation, i.e., it changes directly from a solid to a gaseous state without passing through the liquid phase. The sublimed substance can be collected separately.

3. Obtaining Highly Pure Substances:
Separating mixtures is also essential to obtain highly pure substances. In many scientific and industrial applications, it is necessary to isolate individual components of a mixture with a high degree of purity. This can be achieved through various separation techniques.

- Centrifugation: Centrifugation is used to separate mixtures based on the differences in density or particle size. The mixture is spun rapidly, causing the denser or larger particles to settle at the bottom, while the lighter or smaller particles remain in the liquid or on top.
- Decantation: Decantation is a simple method used to separate a mixture of a solid settled at the bottom of a container and a liquid. The liquid is carefully poured off, leaving the solid behind.
- Electrolysis: Electro