Olympiad Test: Sorting And Separation Of Materials -1 - Class 6 MCQ

Alum is added to purify water as Aluminium Sulphate. It is a coagulant. When Alum is added to the muddy water, the mud particles accumulate to settle down.

Threshing is the process of separating the grains from the stalks or husks of plants, such as wheat, rice, and barley. This is usually done by beating the plant material to release the grains.

• Winnowing is a process used after threshing to separate the lighter chaff from the heavier grains, often using wind or a fan.
• Sieving is the process of separating materials based on size by using a sieve.
• Handpicking is the manual removal of unwanted materials or selection of grains.

So, the correct term for separating grains from the stalks is threshing.

Sieving is defined as a method in which two or more components of different sizes are separated from a mixture on the basis of the difference in their sizes. Thus, it cannot separate two substances in a mixture which have the same size. For example, it cannot separate a mixture of chalk powder from flour.

When a bottle of soda water is sealed, the carbon dioxide (CO2) gas is dissolved in the water under high pressure. When you open the bottle, the pressure is released, and as a result, the solubility of carbon dioxide in the water decreases. This decrease in solubility causes the carbon dioxide to escape from the liquid, producing the fizz that you observe. Temperature also plays a role, as gases are generally less soluble in liquids at lower temperatures, but the primary factor here is the decrease in pressure when the bottle is opened.

Churning is the process used to separate butter from curd. In this process, curd is stirred or churned to separate the solid butter from the liquid buttermilk. This is commonly done using a churner or by hand in some traditional methods.

• Filtration is the process of separating solids from liquids using a filter.
• Heating is used for various processes like melting or boiling but is not used for separating butter from curd.
• Sieving is used to separate materials based on particle size, like flour from bran, but is not used for separating butter from curd.

Thus, churning is the correct process for separating butter from curd.

• High rigidity: Solids have a fixed shape and volume, meaning they are rigid and cannot be easily deformed.
• Regular shape: Many solids have a fixed and regular shape, though some might have irregular shapes, they still retain their shape.
• High density: Solids usually have a higher density compared to liquids and gases, because the particles in solids are closely packed.
• High compressibility: Solids are not easily compressible. The particles in solids are tightly packed, so they cannot be compressed easily, unlike gases which are highly compressible.

Thus, high compressibility is not a characteristic of solids.

When you blow air into the balloon, the air particles inside the balloon move around and collide with the balloon's walls. This creates pressure on the walls of the balloon, causing it to inflate. The elasticity of the rubber material of the balloon (Option C) allows it to stretch and expand as the pressure increases.

Graphite is a good conductor of heat because it has free electrons that allow heat to pass through it efficiently. The other materials listed—glass, rubber, and wood—are poor conductors of heat and are considered insulators.

Sedimentation is the process in which solid particles in a liquid settle down due to gravity. This typically occurs when a suspension is left undisturbed for a period of time, allowing heavier particles to fall to the bottom.

Wind winnowing is an agricultural method developed by ancient cultures for separating grain from straw. It can also be used to remove pests from stored grain. Winnowing usually follows threshing in grain preparation.

Handpicking is an effective method for separating solid mixtures, especially when the components are large enough to be easily distinguished and separated by hand, such as in the case of separating stones from rice or seeds from grains.

- Baking a cake is an example of an irreversible change.
- When you bake a cake, ingredients like flour, sugar, and eggs undergo chemical changes.
- These changes result in a new substance with different properties, which cannot revert to the original ingredients.
- In contrast, freezing or boiling water involves physical changes where the water can return to its original state (liquid water) without changing its chemical structure.

Sieving is a method used to separate solid particles of different sizes. In this case, Rehan can use a sieve to separate the beads (larger particles) from the flour (smaller particles). The flour will pass through the sieve, while the beads will be left behind.

As Saimaa adds more coffee powder to her drink, the coffee powder will dissolve in the water up to a certain limit. Once the solution reaches its maximum capacity to dissolve the coffee powder, no more powder will dissolve, and the solution will become saturated. At this point, any additional coffee powder will remain undissolved in the drink.

This statement is incorrect. The rate at which a solid dissolves in a liquid can be changed by factors like:

• Temperature: Higher temperatures generally speed up the dissolution process.
• Stirring: Stirring the solution helps the solid dissolve faster.
• Surface Area: Finer particles of the solid dissolve more quickly because they have a larger surface area in contact with the solvent.

The other statements (A, B, and C) are correct:

• A: Solids that dissolve in a liquid are considered soluble.
• B: When a solid dissolves in a liquid, the mixture is called a solution.
• C: A change in the color of the liquid can indicate that the solid has dissolved, as in the case of certain solids like sugar or salt.

The primary function of a teabag is to filter the tea leaves while allowing the water to pass through. The teabag keeps the tea leaves contained within it, so they don't mix with the water, while allowing the flavor and color of the tea to infuse into the water.

A solution is formed when a substance dissolves completely in a liquid, creating a homogeneous mixture.

• Chalk powder (Student A): Chalk powder does not dissolve in water; it forms a suspension.
• Salt (Student B): Salt dissolves completely in water, forming a solution.
• Sand (Student C): Sand does not dissolve in water; it forms a suspension.
• Sugar (Student D): Sugar dissolves completely in water, forming a solution.

Therefore, Students B and D will obtain a solution.

The correct sequence for separating the given mixture of materials (pencils, iron nails, copper nails, sand, and sugar) should be:

1. Remove the pencils by sorting them by hand.
2. Use a magnet to separate the iron nails from the mixture.
3. Use a sieve to separate the copper nails (not by hand).
4. Pour water into the mixture of sand and sugar to dissolve the sugar.
5. Use filtration to separate the sand from the sugar solution.
6. Use evaporation to obtain the sugar from the solution.

The incorrect steps are:

• Step 3, pouring water into the mixture should come after the iron nails and copper nails are removed (step 2 and 4).
• Step 4 mentions using a sieve to separate the copper nails, but this should have been done after removing the iron nails, not after adding water.

Hence, Step 3 and Step 4 are out of sequence.

When materials are classified, properties like solubility, conductivity, and transparency are considered because they are related to how the material interacts with other substances or energy. These properties help classify materials into categories like metals, insulators, conductors, soluble or insoluble, transparent or opaque, etc.

However, mass is not a property used for classification, as it is a quantitative measure that does not determine the type or category of a material in a general classification system.

A true solution is a homogeneous mixture where the solute completely dissolves in the solvent, forming a single phase. In this case, salt (solute) dissolves completely in water (solvent), forming a true solution. The particles of salt are too small to be seen and do not settle out.

• Mixture of starch and water forms a suspension where the starch particles don't completely dissolve and may settle over time.
• Mixture of oil and water forms a heterogeneous mixture (emulsion) where oil and water do not mix completely.
• Mixture of sand and water is also a heterogeneous mixture where sand does not dissolve in water and settles at the bottom.

Thus, the mixture of salt and water is a true solution.