Question

Describe a method that could be used to separate each mixture. \(\begin{array}{ll}{\text { a. iron filings and sand }} & {\text { c. the components of ink }} \\ {\text { b. sand and salt }} & {\text { d. helium and oxygen gases }}\end{array}\)

Short answer

Mixture a: Use a magnet to separate iron filings from the sand. Mixture b: Dissolve the salt in water, filter the sand, and evaporate the water to collect the salt. Mixture c: Use chromatography to separate and identify the components of ink. Mixture d: Separate helium and oxygen gases using fractional distillation by liquefying one gas and then evaporating it to collect the pure gas.

Step-by-step solution

Mixture a: Iron filings and sand

Method: Use a magnet to separate the iron filings from the sand. Place a magnet close to the mixture, and the iron filings will be attracted to the magnet, leaving the sand behind. Repeat the process multiple times to ensure that all iron filings are removed.

Mixture b: Sand and salt

Method: Dissolve the salt in water and then filter the sand away. Dissolve the mixture in water and the salt will dissolve, while the sand remains undissolved. Pour the mixture through a filter, and the sand will be trapped on the filter, while the saltwater will pass through. Finally, to separate the salt from the water, evaporate the water using heat; the salt will crystallize and can be collected.

Mixture c: Components of ink

Method: Chromatography Place a drop of ink on a piece of chromatography paper or filter paper. Dip one end of the paper into a solvent (like water or alcohol), and let the solvent travel up the paper. Different components of the ink will travel at different rates, causing them to spread out and separate. This will allow you to observe and identify the different components of the ink.

Mixture d: Helium and oxygen gases

Method: Fractional distillation Lower the temperature of the gas mixture until it reaches a point where one gas (either helium or oxygen) reaches its boiling point and liquefies, while the other gas remains in the gaseous state. Separate the liquid from the gas using a separator. Then, slowly raise the temperature of the liquid until it evaporates, and collect it as the pure gas.

Key concepts

Magnetic Separation

Magnetic separation is a technique used to separate materials with different magnetic properties.

For example, if you have a mixture of iron filings and sand, you can use a magnet to effortlessly pull the iron filings from the sand because iron is a magnetic material while sand is not. This is a simple and effective method to separate components without altering them chemically. In practical applications, magnetic separation can also be used to sort metals from nonmetals in recycling processes.

Filtration and Evaporation

Filtration is commonly paired with evaporation to separate mixtures of solids and liquids.

Consider a mixture of sand and salt. Dissolve the salt in water, and what you have is a solution of saltwater with sand. By filtering this mixture, the solid sand will be trapped on the filter while the saltwater passes through. This process is highly beneficial in not only labs but also in water purification systems. After filtration, evaporation comes into play by heating the saltwater. The water turns into vapor and the salt remains, reverting it back to a solid state. These techniques are both simple and effective for separating mixtures and are essential skills in a chemist's repertoire.

Chromatography

Chromatography is a sophisticated method used to separate and analyze the components of a mixture.

It's especially useful for mixtures like ink, which contains multiple components. By placing a drop of ink on chromatography paper and exposing it to a solvent, the mixture will separate as the solvent travels up the paper. This happens because the different substances in the ink will travel at varying rates based on their solubility, size, and attraction to the paper. Chromatography is a powerful technique used in forensic science, food testing, and in measuring air and water pollutants.

Fractional Distillation

Fractional distillation is a method used to separate a mixture of liquids or gases with different boiling points.

This technique is crucial when dealing with a mixture of helium and oxygen gases. By cooling the mixture, one component can be liquefied while the other remains gaseous, which allows for their separation. Controlled heating can then separate the two substances. Fractional distillation is commonly used in chemical labs and industries, such as in the purification of crude oil into its components like gasoline, diesel, and kerosene.