Question

Identify the following as characteristic of a solution, a colloid, or a suspension: a, a mixture that cannot be separated by a semipermeable membrane b. a mixture that settles out upon standing

Short answer

a. Solutionb. Suspension

Step-by-step solution

- Understand the Concepts

First, understand the definitions: a solution is a homogeneous mixture where particles are at the molecular level, a colloid is a mixture where particle size is intermediate and does not settle out, and a suspension is a heterogeneous mixture with large particles that settle over time.

- Analyze Statement a

A mixture that cannot be separated by a semipermeable membrane typically has particles that are small enough to pass through it. Solutes in a true solution are able to do this, which makes statement a characteristic of a solution.

- Analyze Statement b

A mixture that settles out upon standing indicates that the particles are large enough to be affected by gravity and will sink to the bottom over time, which is characteristic of a suspension.

Key concepts

solution

A solution is a type of homogeneous mixture. This means that the components are evenly distributed throughout the mixture and cannot be distinguished from one another. In a solution, particles are present at the molecular or ionic level, making them extremely small. Because of their small size, they cannot be seen with the naked eye and do not settle out even if the solution is left standing for a long period.
For example:

• Saltwater
• Sugar dissolved in water

A key characteristic of solutions is that they cannot be separated by a semipermeable membrane. This is because the particles are so small that they can easily pass through the pores of these membranes. Thus, if you encounter a mixture that cannot be separated by a semipermeable membrane, it is most likely a solution.

colloid

A colloid is an intermediate type of mixture, falling between solutions and suspensions. In colloids, the particle size is larger than that in solutions but smaller than that in suspensions. The particles in a colloid range from 1 nanometer to 1 micrometer in diameter.
Some examples of colloids include:

• Milk
• Whipped cream
• Gelatin

Unlike suspensions, the particles in colloids do not settle out over time, and the mixture remains uniform. However, colloids can exhibit the Tyndall effect, where light is scattered by the larger particles within the mixture. If a mixture looks uniform to the naked eye but can scatter light, it might be a colloid.

suspension

A suspension is a heterogeneous mixture, meaning that its components can be distinctly recognized. In a suspension, large particles are dispersed within a liquid but remain large enough that they do not dissolve.
Examples of suspensions include:

• Sand in water
• Muddy water

A key characteristic of suspensions is that the particles will eventually settle out upon standing due to gravity. This settling happens because the particles are too large to stay mixed uniformly with the liquid. In conclusion, if you see a mixture where the particles settle out over time, it is most likely a suspension, which aligns with the second statement in the exercise.