Answer key

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Last edited 25 days ago by Learn LoopHQ.

Chapter: 04. Mixtures Separations Of Mixtures

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Separating this three-component mixture requires a sequence of methods. First, magnetic separation is used to remove the iron filings because iron is magnetic, unlike chalk powder and salt. Next, water is added to the remaining chalk powder and common salt, causing the salt to dissolve while chalk powder remains undissolved. Then, filtration is performed; the chalk powder (insoluble solid) is retained on the filter paper as residue, and the salt solution passes through as filtrate. Finally, the salt is recovered from the solution by evaporation, heating the salt solution to vaporize the water and leave the solid salt behind.

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Mixtures and compounds differ fundamentally in how their constituent substances are combined. In a mixture, substances are physically mixed in any proportion and retain their original properties, like sand and iron filings which can be separated by a magnet. In contrast, a compound involves elements chemically combined in a fixed proportion by mass, forming a new substance with entirely different properties, such as water formed from hydrogen and oxygen. Components of mixtures can be separated by simple physical methods, whereas compounds require complex chemical processes to break them down.

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A mixture is characterized by its components being physically combined, not chemically. This means that each substance in the mixture retains its individual properties, unlike in a compound where new properties emerge. Mixtures also have a variable composition, allowing components to be present in any proportion, which in turn leads to no fixed melting or boiling points. Furthermore, the components of a mixture can be separated by simple physical methods without requiring complex chemical reactions.

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Sedimentation and decantation are used to separate insoluble, heavier solid particles from a liquid in a heterogeneous mixture. Sedimentation is the initial step where the heavier solid particles are allowed to settle down at the bottom of the liquid due to gravity, forming a layer called the sediment. The clear liquid above the sediment is known as the supernatant. Decantation then involves carefully pouring off this supernatant liquid into another vessel without disturbing the settled sediment. For example, a mixture of sand and water can be separated; sand settles (sedimentation), and clear water is poured off (decantation).

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Separating components from mixtures is crucial for several reasons in daily life and industry. Firstly, it allows us to remove undesirable or harmful substances, like separating small stones from rice before cooking to ensure safety and quality. Secondly, separation enables us to obtain useful components from a mixture, such as extracting common salt from seawater for consumption, or various fuels like petrol and diesel from crude oil. Lastly, separation is necessary to get a pure sample of a substance, as seen when purifying tap water to obtain distilled water for specific uses.

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