Question

While studying mixtures and solutions, I read that glass is a mixture and not a solution.

Then I searched over the Internet about it, but I got the same answer that it is a homogenous mixture.

But nowhere did I find any meaningful answer about what the difference is in a homogeneous mixture and solution.

People talked about particle size. But if we zoom enough even salt in water is not completely homogeneous.

So, I got some questions here:

Is there any difference in a homogenous mixture and solution?

Is there any clear cut boundary of what size particle are considered a solution or mixture?

Why is brass or any other alloy considered a solution while glass is not?

Last, but not least - Why is air not a solution despite oxygen, nitrogen, etc. molecules being so small?

Answer 1

A homogeneous mixture is a uniformly mixed substance, while a solution is a specific type of homogeneous mixture where particles, typically smaller than 2.0 nm, are dissolved at a molecular or ionic level without settling out. Glass is an amorphous solid and doesn't fit neatly into these categories.

Step-by-step explanation:

Distinguishing Between Homogeneous Mixtures and Solutions

A homogeneous mixture is a combination of two or more substances that are so intimately mixed that the mixture behaves as though it's a single substance. In contrast, a solution is a type of homogeneous mixture where one substance is completely dissolved in another at the molecular or ionic level. The key difference is based on the size of particles present in the mixture.

Solutions have particles the size of ions or small molecules, typically ranging from ~0.1-2.0 nm. An example is salt dissolved in water, where the NaCl disperses uniformly at an ionic level. Colloids have larger particles, ~2.0-500 nm, such as those in milk or fog. Mixtures like suspensions contain even larger particles that are visible and will settle upon standing.

There isn't a clear-cut boundary for particle size that defines a solution versus a mixture, but the general guideline is that particles in a solution are smaller than 2.0 nm. Therefore, the mixture of air, for example, is considered a solution of small gas molecules that do not visibly separate under normal conditions. Similarly, brass, an alloy of copper and zinc, is considered a solution on a molecular level as these metals mix uniformly when molten and retain this uniformity upon solidification.

Glass, though often called a homogeneous mixture, doesn't fit neatly into these categories because it's an amorphous solid where the particles are not arranged in a regular lattice but are too small to be seen as distinct phases, so it doesn't strictly qualify as a classic solution despite its uniformity.