Properties of Water- The Universal Solvent - Online Tutor, Practice Problems & Exam Prep

Water is known as the universal solvent due to its ability to dissolve various solutes, such as salts and biological molecules. Solvents, like water, are present in larger amounts and facilitate the dissolution of solutes, which are typically found in smaller quantities. Solutions can be classified as homogeneous, where components are evenly distributed, or heterogeneous, where they are not. Additionally, substances are categorized as hydrophilic, which dissolve easily in water, or hydrophobic, which do not mix well with water, impacting biological interactions and processes.

Properties of Water- The Universal Solvent

In this video, we're going to continue talking about the properties of water, specifically how water can act as the universal solvent. Now water is described as the universal solvent because water is capable of dissolving so many different types of solutes, and so we need to differentiate between the term solvent and solutes. And so the solvent is defined as the substance that does the dissolving and usually the solvent is going to be found in larger amounts. And when we're referring to life, usually the solvent is going to be water itself. And because water can dissolve so many different types of biological molecules, we call it the universal solvent.

Now the solute on the other hand is defined as the substance that gets dissolved by the solvent, which does the dissolving. And so usually the solute is going to be found in much smaller amounts. And so if we take a look at our image down below at our example, we can differentiate between the solvent and the solute. And so we're looking at an example of table salt or NaCl, sodium chloride, being dissolved in water. And so notice on the left here we have our sodium chloride, the table salt, and on the right we have the sodium chloride being poured into our water.

And so over here on the left hand side when we're just looking at the table salt, recall that it's made up of sodium chloride molecules and the sodium chloride molecules form ionic bonds between the sodium cation which is positively charged and the chloride anion which is negatively charged. And so there is an intact ionic bond forming between these 2 ions. However, when we take the table salt and we dissolve the table salt into the water, as we see over here, what you'll notice is that the ionic bonds are being disrupted and so we have disrupted ionic bonds. And so the sodium cation is not capable of forming an ionic bond with the chloride anion, mainly because the water molecules that are surrounding them are disrupting the potential for them to form ionic bonds. And so notice that the water here in this scenario is what is doing the dissolving.

And so the water is going to be found in larger amounts. It's what's doing the dissolving, and so the water is going to be the solvent. And so notice up above, the solvent is a substance that does the dissolving, usually found in larger amounts and usually going to be water when we're referring to life. And so, of course, this means that the solute is going to be the sodium chloride. And so the sodium chloride is what is getting dissolved by the solvent.

And so we can say here that the sodium chloride is going to be the solute. And so when we take the combination of all of the solutes and the solvent, what we get is the solution. And so really the solution is the combination of the solute and the solvent. And so if we take a look at our text up above, notice we're defining the solution as the combination of the solute and the solvent. Now when we take a look at the solution that we have down below over here on the right-hand side, because water is acting as the solvent, we call this an aqueous solution.

And so an aqueous solution is just a solution in which water acts as the solvent. And so you can see aqueous kinda sounds like aqua, like aquaman for instance, and this is referring to water being the solvent in the solution. And so also notice that the water molecules in the solution are going to form what's known as a hydration shell around the dissolved solute molecules. And so when we take a look at the dissolved solute molecules over here, the sodium and the chloride, notice that they are being surrounded by what's known as a hydration shell, which is when water molecules surround the substance and interact with the substance to dissolve them. And so, this here really concludes our introduction to the lesson on how water acts as the universal solvent and can dissolve so many different types of solutes.

And moving forward in our course, we'll talk about how water can dissolve most of the biological solutions, most of the biological molecules that we'll talk about moving forward, such as proteins, nucleic acids, and carbohydrates. And so, this here concludes our lesson, and we'll be able to get some practice applying these concepts in our next few videos. So I'll see you all there.

A solution in which water is the solvent is called a(n) _______________ solution.

• A. Polar.
• B. Aqueous.
• C. Hydrophobic.
• D. Complete.

The substance in a mixture that is dissolved is called the:

• A. Solution.
• B. Solvent.
• C. Solute.
• D. Aqueous solution.

What is the charge of the solute molecule in the image below based on the polarity of water?

• A. Positively charged.
• B. Negatively charged.
• C. Uncharged.
• D. Non-polar and hydrophobic.

Homogenous vs. Heterogenous Solutions

In this video, we're going to distinguish between 2 different types of solutions, homogeneous solutions versus heterogeneous solutions. Now, homogeneous solutions have this prefix homo in it, which we know means the same. And so homogeneous solutions are going to be uniformly mixed solutions where all parts are the same or evenly distributed. And so heterogeneous solutions, on the other hand, have the prefix hetero, which means different. And so heterogeneous solutions are going to be mixed solutions where parts are unequally distributed or unevenly distributed.

And so when we take a look at our image down below, we can better distinguish between homogeneous and heterogeneous solutions. So on the left-hand side over here, notice that we have 2 different solutes dissolved in this beaker. We have the blue solutes and then we have the red solutes that we see throughout. And so, notice that the blue and the red solutes are pretty evenly distributed throughout the beaker, and so this is therefore going to be referred to as a homogeneous solution. Whereas over here on the right-hand side, notice that we also have the same blue solutes and red solutes.

However, notice that they are not equally distributed throughout the beaker. They are unequally distributed. Notice that the red ones are towards the top half of the beaker, whereas the blue ones are towards the bottom half of the beaker. So that is an unequal distribution throughout the beaker. And so this makes this a heterogeneous solution.

Once again, hetero meaning different and homo meaning the same, so evenly distributed versus hetero being different and being unevenly distributed. So really this here concludes our lesson on the difference between homogeneous and heterogeneous solutions, and we'll be able to get a bit of practice moving forward in our course. So I'll see you all in our next video.

The components of a heterogenous solution are ________________ distributed throughout.

• A. Equally.
• B. Unequally.
• C. Uniformly.

Hydrophilic vs. Hydrophobic

In this video, we're going to distinguish between hydrophilic and hydrophobic substances. Although water is known as the universal solvent because it can dissolve so many different substances, water cannot dissolve all substances. In fact, water can only dissolve substances that are hydrophilic. Hydrophilic is a word that describes substances that dissolve really easily in water due to having an affinity to water. Hydrophilic means "water loving" because the "hydro" prefix means water, and the "phyllic" root is Greek for loving.

Substances that are hydrophilic are water loving, meaning that they interact nicely with the water and dissolve well in it. Now, substances that are polar and charged tend to be hydrophilic, for example, salts and ions. On the other hand, water will not dissolve substances that are hydrophobic. Hydrophobic is a term that describes substances that do not dissolve in water, making hydrophobic substances water fearing. Again, because "hydro" means water and "phobic" means fearing.

Like people that have a phobia have some kind of fear. It's really the non-polar molecules that tend to be hydrophobic. For example, fats, oils, and waxes, which we'll talk more about later in our course. But down below in our example, you can see that we're showing you the difference between hydrophobic and hydrophilic substances. You can see we're looking at salt versus oil in water.

On the left-hand side, in blue, we're showing salt being sprinkled into water, and the salt, we recall, is sodium chloride. You can see the sodium ion here, the chloride ion over here when we zoom in, and so the sodium and the chloride have charges on them. They are charged molecules, they are ions, and so they are hydrophilic for that reason, water loving. They interact and mix nicely with water. On the other hand, on the right-hand side, we're showing oil dissolved in water.

If you go into your kitchen and take some vegetable oil and pour it into the water, what you'll notice is that the oil does not mix nicely with the water. No matter how much you stir the oil and water together, eventually, the oil will separate out from the water. And so the oil is hydrophobic. It does not dissolve well in water. It is water fearing.

This concludes our lesson on the difference between hydrophilic and hydrophobic substances, and we'll be able to get some practice as we move along in our course. So I'll see you all in our next video.

Hydrophobic molecules:

• A. Are polar covalent molecules.
• B. Easily dissolve in water.
• C. Are nonpolar water 'fearing' molecules.
• D. Are nonpolar water 'loving' molecules.

Here’s what students ask on this topic:

Why is water considered the universal solvent?

Water is considered the universal solvent because it can dissolve a wide variety of substances. This ability is due to its polar nature, where the oxygen atom has a partial negative charge, and the hydrogen atoms have partial positive charges. This polarity allows water molecules to surround and interact with various solutes, such as salts and biological molecules, effectively breaking their bonds and dissolving them. This property is crucial for many biological processes, as it enables the transport and reaction of different molecules within living organisms.

What is the difference between a solvent and a solute?

A solvent is a substance that dissolves other substances, known as solutes. In a solution, the solvent is typically present in a larger amount, while the solute is present in a smaller amount. For example, in a saltwater solution, water acts as the solvent, and salt (sodium chloride) is the solute. The solvent facilitates the dissolution process by surrounding the solute particles and breaking their bonds, leading to a homogeneous mixture.

What are homogeneous and heterogeneous solutions?

Homogeneous solutions are mixtures where the solute is evenly distributed throughout the solvent, resulting in a uniform composition. An example is salt dissolved in water. Heterogeneous solutions, on the other hand, have an uneven distribution of solute particles, leading to a non-uniform composition. An example is a mixture of oil and water, where the oil does not dissolve and remains separate from the water.

What is the difference between hydrophilic and hydrophobic substances?

Hydrophilic substances are water-loving and dissolve easily in water due to their polar nature or charge. Examples include salts and ions. Hydrophobic substances are water-fearing and do not dissolve well in water because they are non-polar. Examples include fats, oils, and waxes. This distinction is important in biological systems, as it affects how molecules interact and function within aqueous environments.

How does water dissolve ionic compounds like sodium chloride?

Water dissolves ionic compounds like sodium chloride (NaCl) by surrounding the individual ions with water molecules. The partial negative charge of the oxygen atom in water attracts the positively charged sodium ions (Na⁺), while the partial positive charge of the hydrogen atoms attracts the negatively charged chloride ions (Cl⁻). This interaction disrupts the ionic bonds in NaCl, leading to the formation of a solution where the ions are evenly distributed and surrounded by water molecules, known as a hydration shell.