Problem 58 - Chemistry Matter and Change

Question

Describe a method that could be used to separate each mixture. \begin{equation} \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} \end{equation}

Step-by-Step Solution

Answer

Use a magnet for iron and sand, dissolve then filter for sand and salt, chromatography for ink, and fractional distillation for gases.

Step 1: Iron Filings and Sand

To separate iron filings from sand, use a magnet. Iron filings are attracted to the magnet due to their magnetic properties, leaving the sand behind. Simply pass a strong magnet over the mixture several times until all the iron filings have been removed.

Step 2: Sand and Salt

To separate sand from salt, add water to the mixture and stir. Salt dissolves in water while sand does not. Filter the mixture to separate the sand from the saltwater solution. After filtering, evaporate the water from the saltwater solution to retrieve the salt.

Step 3: Ink Components

Use chromatography to separate the components of ink. Place a small dot of the ink on a strip of chromatography paper and dip it into a solvent. As the solvent moves up the paper, different ink components will travel at different rates, enabling them to be separated based on their solubility.

Step 4: Helium and Oxygen Gases

Separate helium and oxygen gases using fractional distillation. Cool the gaseous mixture until it becomes liquid, then gradually heat it. Helium has a lower boiling point than oxygen and will evaporate first, allowing it to be collected separately from the oxygen.

Key Concepts

Magnetic Separation

Magnetic separation is a process that utilizes the magnetic properties of a substance to extract it from a mixture. This technique is particularly useful when separating iron filings from non-magnetic substances like sand. To carry out magnetic separation:

• Use a strong magnet and pass it over the mixture.
• The iron filings will be attracted to the magnet, leaving the non-magnetic material behind.
• Repeat the process to ensure all iron particles are collected.

This method is effective because iron is ferromagnetic, meaning it has strong magnetic properties allowing it to bind to the magnet quickly. This technique provides a straightforward yet ingenious solution when dealing with mixtures of magnetic and non-magnetic components.

Filtration and Evaporation

Filtration and evaporation are combined techniques that can efficiently separate a mixture of sand and salt. Here's how it works: **Filtration Process**

• Add water to the sand-salt mixture and stir. The salt dissolves in the water, but the sand remains unaffected.
• Use a filter paper and funnel to separate the undissolved sand from the saltwater solution.
• The sand will remain on the filter paper, while the saltwater passes through.

**Evaporation Process**

• Heat the saltwater solution gently until all the water evaporates.
• As the water evaporates, the salt is left as a residue in the dish.

This dual-process technique makes separation of insoluble and soluble components efficient and practical, ensuring complete recovery of the salt from the mixture.

Chromatography

Chromatography is a versatile and sophisticated method used for separating different components of a mixture, such as the components of ink. This is particularly useful in analyzing complex mixtures. Here's how to perform chromatography:

• Draw a small dot of ink on a strip of chromatography paper.
• Place the bottom of the paper into a solvent without submerging the ink.
• As the solvent travels up the paper, it carries the different ink components with it.
• Each ink component moves at a different speed depending on its solubility and affinity to the paper, creating distinct colored bands.

This method relies on the principle that different substances will have varying solubilities and attractions to the solvent and paper, allowing the separation and identification of individual components through visible layers.

Fractional Distillation

Fractional distillation is a powerful technique used to separate components of a mixture based on differences in their boiling points. It's especially useful for separating gases like helium and oxygen.

• First, cool the gaseous mixture until it becomes a liquid.
• Gradually heat the liquid mixture. The component with the lower boiling point, like helium, will boil and evaporate first.
• Collect the evaporated gas, while the component with the higher boiling point remains in liquid form.

This process is iterative, meaning it might need to be performed multiple times for purity. Fractional distillation is invaluable in chemical industries to purify substances and obtain gases in their pure forms.