Heterogeneous vs Homogeneous Mixtures Explained

The question asks us to identify which of the given options is NOT a heterogeneous mixture. This means we are looking for a homogeneous mixture.

Let's understand the difference:

• Heterogeneous Mixture: A mixture where the components are not uniformly distributed throughout. You can often see different parts or phases. Examples include sand in water or oil and vinegar.
• Homogeneous Mixture: A mixture where the components are uniformly distributed. It looks the same throughout, and you cannot distinguish the different components with the naked eye. Solutions are examples of homogeneous mixtures.

Analyzing the Options

Option 1: Sulphur in carbon disulphide

Carbon disulfide (\(CS_2\)) is a liquid solvent. Sulphur is known to dissolve in carbon disulfide. When a substance dissolves completely in another, it forms a solution. Solutions are uniformly distributed and are therefore homogeneous mixtures. Since sulphur dissolves in carbon disulfide, this mixture is homogeneous.

Option 2: Mixture of sugar and salt crystals

Mixing solid sugar crystals and solid salt crystals creates a mixture where distinct particles of sugar and salt are present. Although both are solids, they are not chemically bonded and maintain their individual identities. Unless dissolved in a solvent, a physical mixture of two different solid crystalline substances is generally considered heterogeneous because the composition is not uniform at a microscopic level (you have particles of pure salt and particles of pure sugar).

Option 3: Sandy water

Sand particles do not dissolve in water. They remain suspended for a while but eventually settle down due to gravity. You can clearly see the separate sand particles and the water. This non-uniform composition makes sandy water a classic example of a heterogeneous mixture (specifically, a suspension).

Option 4: Sulphur in water

Sulphur is insoluble in water. When added to water, sulphur particles do not dissolve and will either float on the surface or settle at the bottom. You can visibly distinguish between the sulphur particles and the water. This makes the mixture heterogeneous.

Conclusion

Based on the analysis:

• Sulphur in carbon disulphide forms a solution (homogeneous).
• Mixture of sugar and salt crystals is heterogeneous (as solids).
• Sandy water is heterogeneous (suspension).
• Sulphur in water is heterogeneous (insoluble substance).

Therefore, the mixture that is NOT heterogeneous is Sulphur in carbon disulphide.