Solutions - Online Tutor, Practice Problems & Exam Prep

Solutions are homogeneous mixtures consisting of a solute, which is the smaller component, and a solvent, the larger component that dissolves the solute. Concentration measures the amount of solute in a solution. In contrast, suspensions are heterogeneous mixtures with larger particles that can settle, while colloids contain intermediate-sized particles that remain suspended. For example, Italian salad dressing is a suspension, and milk is a colloid. Understanding these distinctions is crucial for grasping concepts in chemistry, particularly in relation to mixtures and their properties.

Solutions

Solutions represent homogeneous mixtures made up of 2 or more components that form a uniform composition. Now, when we say uniform composition, that means that everything mixes perfectly together. So when I take a look at the result, I can't tell which part is which. Everything is mixed perfectly together. Now, when it comes to solutions, we have portions of it that we need to understand. First, we have our solute. The solute represents the smaller portion of the solution that is dissolved within the solvent. The solvent itself is the part of the solution that is present in the larger amount and it can dissolve other substances.

Concentration is a word that you will hear often. Concentration is basically a measurement of the amount of solute that you have present in a given solution. So, speaking about solutions, let's take a look at this solution formation image. The smaller ball there, it's smaller in amount, so it represents our solute. This solute, I'm going to dunk it into this solvent, let's just assume it's water, which is larger in amount, then you need to realize when you have a solute dissolving in a solvent, they create a purple solution in this case, which is our solution. So just remember, solutions are homogeneous mixtures and it is the solute added to the solvent that helps to create them.

Solutions Example 1

Here it says, if 10 grams of sodium chloride is dissolved in 500 ml of water, identify the solute and the solvent. Remember, the solute is the smaller portion of our solution. It's the quantity that's lower in amount. So here we're going to say that our solute within this question would have to be the 10 grams of sodium chloride. And then here the solvent is the larger portion that does the dissolving. The larger portion here is the water. So water here would be our solvent. So within this question, our solute again is sodium chloride and our solvent is water. Together they form our solution.

Solutions

We just said that solutions represent homogeneous mixtures. When it comes to mixtures, solutions aren't the only important term to remember. We also have suspensions and colloids. Suspensions represent heterogeneous mixtures. In these heterogeneous mixtures, we have large solute particles that have the potential to float within the solvent. Then we have colloids. Colloids represent yet another homogeneous mixture. The difference now, in solutions, the particles completely dissolve within our solvent, so they're not easy to see. But in a colloid, there are intermediately sized particles that can also float within a solvent.

When it comes to their particle sizes, we're going to say for suspensions, the particles are larger so they tend to be greater than 500 nanometers in terms of size. And for colloids, they tend to be less than 500 nanometers. Because of their increased size, because they're larger, these particles will eventually settle, and they could settle either on the top or on the bottom. Where they settle really depends on the density of the solvent. But all you need to remember is that when it comes to suspensions, the particles being larger means they can eventually settle. Colloids, though, their particles are not as large. So these particles, they never settle. They never settle on the top or the bottom. They kind of stay suspended somewhere in the middle of the solvent.

Now, what are great examples of suspensions and colloids? Well, a great example for a suspension could be Italian salad dressing. Because in Italian salad dressing, what do we have? We have oil, vinegar, herbs, and spices. And if you really look at Italian dressing, you can see those particles floating around within the liquid. Examples of colloids, a great example would be milk. Now in milk, suspended within the liquid portion of it, you have fat particles, casein, and a lot of different things that are suspended within the milk itself. And these things are constantly floating within milk. They don't settle on the top or the bottom.

So just remember, solutions are homogeneous mixtures, but mixtures also can refer to suspensions and colloids.

Solutions Example 2

Here it says, from the following images identify a solution, a suspension, and a colloid. Alright. So first of all, let's tackle the easier one. A solution represents a homogeneous mixture. The solute has perfectly dissolved within the solvent, so you can't tell them apart. That would mean that option b, you can't see the solute within it because it's been perfectly dissolved. This represents our solution. Then we have a and c. Remember, a colloid because it's heavier particles, it never settles on the top. It's going to sink to the bottom. So c would have to represent our colloid. And then process of elimination, this one here the particles are smaller in size and they're dispersed throughout the solvent. Some of them are dispersed at the top, the middle and the bottom. This would have to represent our suspension. So a would be our suspension, b would be our solution, and c would be our colloid.

Here’s what students ask on this topic:

What is the difference between a solute and a solvent in a solution?

A solute is the smaller component of a solution that gets dissolved, while the solvent is the larger component that dissolves the solute. For example, in a saltwater solution, salt is the solute, and water is the solvent. The solvent's ability to dissolve the solute results in a homogeneous mixture where the solute is uniformly distributed within the solvent.

How do you calculate the concentration of a solution?

Concentration is calculated by dividing the amount of solute by the volume of the solution. The formula is:

$\frac{\mathrm{amount} \mathrm{of} \mathrm{solute}}{\mathrm{volume} \mathrm{of} \mathrm{solution}}$

Common units for concentration include molarity (moles of solute per liter of solution) and mass percent (mass of solute per mass of solution, multiplied by 100).

What are the key differences between solutions, suspensions, and colloids?

Solutions are homogeneous mixtures where the solute is completely dissolved in the solvent, resulting in a uniform composition. Suspensions are heterogeneous mixtures with large solute particles that can settle over time. Colloids are homogeneous mixtures with intermediate-sized particles that remain suspended and do not settle. Examples include saltwater (solution), Italian salad dressing (suspension), and milk (colloid).

Why do particles in a suspension eventually settle, but not in a colloid?

In a suspension, the particles are larger (greater than 500 nanometers) and are influenced by gravity, causing them to settle over time. In a colloid, the particles are smaller (less than 500 nanometers) and are kept suspended by Brownian motion and interactions with the solvent, preventing them from settling.

Can you provide examples of solutions, suspensions, and colloids?

Examples of solutions include saltwater and sugar dissolved in water. Examples of suspensions include Italian salad dressing and muddy water, where particles can be seen floating and eventually settling. Examples of colloids include milk and mayonnaise, where particles remain suspended and do not settle.