Problem 58 - Chemistry for Allied Health

Question

How big are the particles in a colloid compared to those of a suspension and a solution?

Step-by-Step Solution

Answer

Particles in a colloid are larger than those in a solution but smaller than those in a suspension.

Step 1: Understanding the Components

Recognize that the question involves three types of mixtures: colloids, suspensions, and solutions. Each of these has different particle sizes.

Step 2: Comparing Particle Sizes

Realize that the difference lies in the size of the particles within each type of mixture. Generally, particles in a solution are the smallest, typically less than 1 nanometer, while particles in a suspension are the largest, usually over 1000 nanometers.

Step 3: Determining Colloid Particle Size Range

Understand that colloids have particles that are intermediate in size, typically between 1 nanometer and 1000 nanometers. They are larger than those in solutions but smaller than those in suspensions.

Step 4: Final Comparison Conclusion

Conclude that in terms of size: solution particles < colloid particles < suspension particles. This helps in categorizing substances based on their physical characteristics.

Key Concepts

Colloids

Colloids are fascinating mixtures where the particles are intermediate in size compared to solutions and suspensions. These particles range roughly between 1 nanometer and 1000 nanometers. Imagine a cloud or milk; both are colloids. They seem uniform, but if you look closely, tiny particles such as water droplets in fog or fat globules in milk are floating.

Colloids are special because their particles do not settle out over time as in suspensions. This is due to the Brownian motion or the random movement of particles in a fluid, which keeps them suspended. Here are a few key points to help you understand colloids better:

• Particles remain dispersed and stable in size.
• Often appear cloudy or opaque due to light scattering.
• Do not settle out or separate quickly.
• Common examples include whipped cream, jelly, and smoke.

Colloidal systems can be found in various states: solids in liquids (gel), liquids in gases (aerosol), or even solids in gases (smoke). The versatility and unique properties of colloids make them useful in many industrial and day-to-day applications.

Suspensions

Suspensions are types of mixtures where the particles are much larger than those in colloids and solutions. Typically, the particles in a suspension are over 1000 nanometers in size. Consider muddy water or flour mixed in water as simple examples of suspensions. Unlike colloids and solutions, the particles in suspensions are large enough to be seen with the naked eye.

This property makes suspensions interesting because their particles will eventually settle to the bottom over time due to gravity. Some important characteristics of suspensions include:

• Clearly visible particles when mixed.
• Particles eventually settle out of the mixture upon standing.
• Easy to separate through filtration.
• Example items include sand in water and orange juice with pulp.

In suspensions, vigorous stirring may be needed to keep the particles mixed, and they often appear cloudy when initially mixed. The study and application of suspensions are crucial in fields such as medicine, where certain drugs are delivered in this form for easier dosage and absorption.

Solutions

Solutions are homogeneous mixtures where the particles are the tiniest among mixtures, less than 1 nanometer in size. Think of sugar dissolved in water or salt in seawater; these are examples of solutions. Due to their extremely small size, these particles are not visible to the naked eye and cannot be filtered out easily.

Solutions are unique primarily because of their stability and uniform appearance. Several features characterize solutions:

• Particles are evenly distributed and do not settle out.
• Appear clear and transparent with no visible particles.
• Solutes dissolve in the solvent completely.
• Examples include soda, air, and alloys in solid form.

The science of solutions explains why a pinch of salt spreads evenly in water, allowing no clumps to form. This makes solutions a significant subject in chemistry and everyday life where mixing and dissolving are involved.

Mixtures

Mixtures are combinations of two or more substances where each retains its chemical properties. They are extensively categorized into two types: heterogeneous and homogeneous mixtures. Examples of mixtures include salad, air, and granola. Understanding mixtures is essential as they form the cornerstone of many material processes and products around us.

Below are some points that help clarify different types of mixtures:

• Heterogeneous mixtures have visibly different substances or phases. Examples are salads and rock samples.
• Homogeneous mixtures (solutions) appear consistent throughout, like air or vinegar.
• They exhibit varied properties like solubility, particle sizes, and separation ability.

Mixtures are pervasive in both natural systems and human-made creations, embracing everything from the smallest particles in the atmosphere to complex alloys. Recognizing their components helps us understand the nature and transformations of materials in diverse contexts.