Question

Suggest physical changes by which the following mixtures can be separated. (a) iron filings and wood chips (b) ground glass and sucrose (cane sugar) (c) water and olive oil (d) gold flakes and water

Short answer

Iron filings can be separated from wood chips using a magnet. Ground glass can be separated from sucrose using water and then filtering off the ground glass. Water and olive oil can be separated using a separating funnel. Gold flakes can be separated from water using decantation and subsequent filtering.

Step-by-step solution

Separation of Iron Filings and Wood Chips

A magnet can be used to separate a mixture of iron filings and wood chips. Iron is magnetic while wood is not. So, when a magnet is run over the mixture, the iron filings are attracted to it while the wood chips are not afftected.

Separation of Ground Glass and Sucrose (Cane Sugar)

Water can be used to separate a mixture of ground glass and sucrose. Sucrose is soluble in water while glass is not. So, when water is added to the mixture, the sucrose dissolves forming a solution while the ground glass can be filtered off.

Separation of Water and Olive Oil

A separating funnel can be used to separate a mixture of water and olive oil. Water and oil are immiscible, forming two distinct layers with water being denser. By opening the stopcock of the separating funnel, the water will pour out first, leaving the oil behind.

Separation of Gold Flakes and Water

A filter or sieve can be used to separate a mixture of gold flakes and water. Gold being far denser than water will not float but rest at the bottom. By carefully decanting (pouring off the liquid), most of the water can be removed. The remaining gold flakes can be obtained by carefully filtering the remaining liquid.

Key concepts

Magnetic Separation

Magnetic Separation is a handy technique to separate substances based on their magnetic properties. In many mixtures, materials may have different reactions to magnetic fields. This method involves using a magnet to attract magnetic particles away from non-magnetic ones.

For instance, in a mixture of iron filings and wood chips:

• Iron filings are magnetic, while wood chips are not.
• A magnet is brought close to the mixture.
• The iron is attracted to the magnet, separating it from the wood chips easily.

This technique is quick and efficient, minimizing the labor and time needed for separation.

Solubility

Solubility refers to the ability of a substance to dissolve in a solvent, typically water. Some substances dissolve easily, while others do not. This variation can be skillfully leveraged to separate mixtures.

Consider a mixture of ground glass and sucrose:

• Sucrose is highly soluble in water, while ground glass is not.
• Add water to the mixture; sucrose dissolves, leaving the ground glass intact.
• After dissolving, remove the insoluble ground glass by filtration.

This simple method effectively separates soluble from insoluble substances, providing a clear solution.

Density Separation

Density is a property that refers to the mass per unit volume of a substance. Two immiscible liquids (liquids that do not mix) like water and olive oil, can be separated by exploiting their density differences.

Here's how it works:

• Water is denser than olive oil.
• In a container, water settles below the less dense olive oil, creating two layers.
• A separating funnel can be used to easily drain the denser water layer first, leaving the olive oil behind.

Using density differences in separation is pivotal to this technique, making it efficient for various applications.

Decantation and Filtration

Decantation and filtration are classic methods used for separating mixtures, especially those involving solids and liquids. These processes utilize gravity and physical barriers to distinctively extract one component from another.

In separating gold flakes from water, consider the steps:

• Gold flakes are dense and settle at the bottom of a container with water.
• By carefully pouring, or decanting, most of the water can be removed.
• Filtering the remaining liquid helps to gather the gold flakes that may still be wet with water.

These methods offer a pragmatic approach to effectively isolate solid particulates from liquid mediums.