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. In solutions, the solvent (usually water) dissolves the solute, creating an aqueous solution. Solutions can be homogeneous, where components are evenly distributed, or heterogeneous, where they are not. Additionally, substances are classified as hydrophilic (water-loving, easily dissolving) or hydrophobic (water-fearing, not dissolving well). Understanding these properties is crucial for studying biological processes and interactions.

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. We need to differentiate between the term solvent and solutes. The solvent is defined as the substance that does the dissolving and is usually found in larger amounts. When referring to life, the solvent is usually water itself. Because water can dissolve so many different types of biological molecules, we call it the universal solvent.

The solute, on the other hand, is defined as the substance that gets dissolved by the solvent. Usually, the solute is found in much smaller amounts. If we look at our image below at our example, we can differentiate between the solvent and the solute. We're looking at an example of table salt, &#xNaCl; (sodium chloride), being dissolved in water. 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.

On the left-hand side, when we're just looking at the table salt, recall that it's made up of sodium chloride molecules. The sodium chloride molecules form ionic bonds between the sodium cation, which is positively charged, and the chloride anion, which is negatively charged. There is an intact ionic bond forming between these two ions. However, when we take the table salt and dissolve it into the water, what you'll notice is that the ionic bonds are being disrupted. The sodium cation is not capable of forming an ionic bond with the chloride anion mainly because the water molecules surrounding them are disrupting the potential for them to form ionic bonds.

Notice that the water here is what is doing the dissolving. The water is going to be found in larger amounts; it's what's doing the dissolving, making the water the solvent. Of course, this means that the solute is going to be the sodium chloride. When we take the combination of all the solutes and the solvent, what we get is the solution. The solution is the combination of the solute and the solvent. Because water is acting as the solvent, we call this an aqueous solution. An aqueous solution is a solution in which water acts as the solvent.

Also, notice that the water molecules in the solution form what's known as a hydration shell around the dissolved solute molecules. When we take a look at the dissolved solute molecules, the sodium and the chloride, notice that they are being surrounded by a hydration shell. This shell is when water molecules surround the substance and interact with the substance to dissolve them.

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. Moving forward in our course, we'll talk about how water can dissolve most of the biological molecules that we'll discuss, such as proteins, nucleic acids, and carbohydrates. This 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.

• 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.

• 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.

• 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.

• 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 for water. Hydrophilic literally means "water-loving" because the "hydro" prefix means water, and the "philic" 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. Substances that are polar and charged, such as salts and ions, tend to be hydrophilic. On the other hand, water will not dissolve substances that are hydrophobic. "Hydrophobic" describes substances that do not dissolve in water. Hydrophobic substances are "water-fearing" substances because the "hydro" prefix means water, and the "phobic" root means fearing, similar to how people with a phobia have a fear. So, it's the nonpolar molecules that tend to be hydrophobic, such as 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 are showing you the difference between hydrophobic and hydrophilic substances. We are looking at salt versus oil in water. On the left-hand side, in blue, we are showing you salt being sprinkled into water, and the salt, we recall, is sodium chloride. You can see the sodium ion here and the chloride ion over here when we zoom in, and so the sodium and the chloride, being charged molecules - they are ions - are hydrophilic for that reason, water-loving. Thus, they interact and mix nicely with water. In contrast, on the right-hand side, we show you oil dissolved in water. If you go to your kitchen and pour some vegetable oil into the water, what you will notice is that the oil does not mix nicely with water. No matter how much you stir the oil and water together, eventually, the oil will separate out from the water. Thus, the oil is hydrophobic; it does not dissolve well in water and is water-fearing. This concludes our lesson on the difference between hydrophilic and hydrophobic substances, and we'll be able to practice this as we move along in our course. 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.

• 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 the substance that does the dissolving in a solution, typically present in larger amounts. In biological contexts, water is the most common solvent. A solute, on the other hand, is the substance that gets dissolved by the solvent and is usually present in smaller amounts. For example, in a saltwater solution, water is the solvent, and sodium chloride (table salt) is the solute. The combination of solute and solvent forms a solution.

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, however, have an uneven distribution of solute within the solvent, 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 or charged nature. Examples include salts and ions. Hydrophobic substances, on the other hand, 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.

What is an aqueous solution?

An aqueous solution is a solution in which water acts as the solvent. The term 'aqueous' comes from 'aqua,' meaning water. In an aqueous solution, water dissolves various solutes, such as salts, sugars, and gases, facilitating numerous biological and chemical processes. For example, when table salt (NaCl) is dissolved in water, it forms an aqueous solution where the Na⁺ and Cl⁻ ions are surrounded by water molecules.