Question

Explain why a suspension is considered a heterogeneous mixture.

Short answer

A suspension is a heterogeneous mixture because its components are visibly distinguishable and non-uniform.

Step-by-step solution

Define Heterogeneous Mixture

A heterogeneous mixture is a type of mixture in which the composition is not uniform throughout the mixture and different components are visibly distinguishable.

Understand the Characteristics of a Suspension

A suspension is a heterogeneous mixture where solid particles do not dissolve in a liquid solution. These particles are large enough to be seen with the naked eye and will eventually settle out upon standing.

Compare Suspension with Homogeneous Mixture

In a homogeneous mixture, the components are uniformly distributed and the composition is consistent throughout. In contrast, suspensions have visibly separate components and exhibit non-uniform composition.

Observe Visibility of Particles

In a suspension, the particles are large enough to be seen by the naked eye, making it easy to identify the different components of the mixture. This visible difference is a key indicator of a heterogeneous mixture.

Consider Settling Behavior

Over time, the solid particles in a suspension will settle at the bottom if left undisturbed. This settling behavior clearly shows the different phases of the mixture, reinforcing that it is heterogeneous.

Key concepts

suspension characteristics

A suspension is a particular kind of heterogeneous mixture where solid particles do not dissolve but remain dispersed throughout the liquid. Unlike solutions where solutes dissolve into the solvent to create a uniform mixture, suspensions maintain a clear separation between the solid and liquid phases.
Some key characteristics of suspensions include:

• Particle Size: The solid particles within a suspension are relatively large. They are sizable enough to be seen without the aid of a microscope.
• Separation Over Time: Given that the solid particles do not dissolve, they tend to settle at the bottom if the mixture is allowed to sit undisturbed.
• Light Scattering: Suspensions often scatter light due to the larger particle size, making the mixture appear cloudy or murky.

These characteristics make suspensions distinctly different from solutions and colloids.

comparing mixtures

Mixtures can be broadly categorized into homogeneous and heterogeneous types.

• Homogeneous Mixtures: These mixtures have a uniform composition throughout. Examples include saltwater or air. Their components are thoroughly mixed at the molecular level.
• Heterogeneous Mixtures: In these mixtures, the individual components remain distinct and are not uniformly distributed. Examples include salad or a mixture of sand and water. In heterogeneous mixtures, you can often identify different substances visually.

Within heterogeneous mixtures, suspensions and colloids are two common types. These mixtures have visible differences in their composition compared to homogeneous mixtures where everything appears consistent.

visibility of particles

One defining feature of suspensions is the visibility of particles. Due to their larger size, the particles in a suspension can usually be observed with the naked eye. This makes suspensions easy to identify and differentiate from other mixtures.
For instance, in a suspension like muddy water, you can see the distinct soil particles dispersed in the water. Over time, these particles will settle at the bottom, again clearly visible. This contrasts with solutions like saltwater, where the salt particles dissolve entirely, rendering them invisible.
Visibility of particles is not just about being able to see them initially. It's also about the behavior of these particles over time, which is evident in how suspensions settle.

settling behavior

The settling behavior of a suspension is another key indicator that it is a heterogeneous mixture. When left undisturbed, the solid particles in a suspension will gradually settle at the bottom due to gravity.
This process of settling can be easily observed in mixtures like chalk powder in water or orange juice with pulp. Initially, the solid particles are suspended throughout the liquid. Over time, they collect at the bottom, creating a sediment layer.
Settling clearly demonstrates the non-uniform nature of suspensions. The solid particles separate from the liquid phase, reinforcing the idea that the components remain distinct even over time.
This behavior is a clear contrast to homogeneous mixtures, where the components do not separate upon standing, indicating a uniform composition.