Question

Small liquid droplets dispersed in another liquid is called: (a) suspension (b) emulsion (c) gel (d) true solution

Short answer

The correct answer is (b) emulsion.

Step-by-step solution

Understand the Definitions

First, it's important to understand the terminology. A suspension is a heterogeneous mixture where solid particles are dispersed in a liquid. An emulsion is a type of colloid formed by combining two liquids that usually do not mix together. A gel is a semi-solid that is typically soft and can have properties ranging between solid and liquid. A true solution is a homogeneous mixture where a solute is completely dissolved in a solvent.

Identify the correct term

Small liquid droplets dispersed in another liquid describes an emulsion because it is a mixture of two liquids that do not mix forming a colloidal system where one liquid is dispersed throughout the other.

Key concepts

Colloidal Systems

When considering materials at the microscopic level, colloidal systems are a fascinating and diverse group. At its core, a colloid is a mixture where one substance of microscopically dispersed insoluble or soluble particles is suspended throughout another substance.

Imagine tiny spheres of one substance floating through another, but these spheres are so small that gravity doesn't cause them to settle. Examples include fog, milk, and even butter. These systems can exhibit unique characteristics, such as the Tyndall effect, where light is scattered by particles within the colloid, creating a visible beam. Colloids consist of two parts: the dispersed phase (the particles) and the continuous phase (the medium in which particles are dispersed).

Suspension

A suspension differs from a colloid in the size of the particles. In a suspension, the particles are larger and will eventually settle out under the influence of gravity, given sufficient time.

To visualize this, think of a snow globe: when shaken, the snow particles are dispersed throughout the globe but eventually settle at the bottom. This is also true for suspensions; for instance, muddy water left undisturbed will clear as soil particles settle. Suspensions are heterogeneous mixtures, meaning the components can be visually distinguished and separated, typically by filtration or sedimentation.

True Solution

A true solution is quite different from the mixtures discussed so far. Here, the solute particles are completely dissolved at the molecular or ionic level within the solvent, resulting in a homogeneous mixture.

This means the mixture is uniform throughout, and the dissolved substances will not settle or be separated by ordinary physical means. The classic example is salt water: the salt, when completely dissolved, is evenly distributed within the water, creating a transparent solution with consistent properties throughout. True solutions are stable and don't exhibit the Tyndall effect because the particle size is too small to scatter light.

Gel

Gels are fascinating substances that exist somewhere between liquid and solid states. They have the structural cohesiveness of a solid, with a network of connected molecules, but they're also permeated by a liquid that gives them their soft and sometimes spreadable texture.

An example of a gel you might encounter in daily life is jelly, where the liquid component is trapped within a solid framework. In this semi-solid phase, the movement of the dissolved liquid is restricted, which imparts the gel with its unique properties. Gels are considered colloidal systems because they consist of a solid network dispersed through a liquid.