Video Transcript
Which of the following is the most accurate definition of a solution? (A) A solution is a heterogeneous mixture of two substances or more, with different
types that depend on the physical state of each solute and the solvent. (B) A solution is a heterogeneous mixture of two substances or more, with different
types that depend on the density of each solute and the solvent. (C) A solution is a homogeneous mixture of two substances or more, with different
types that depend on the physical state of each solute and the solvent. (D) A solution is a homogeneous mixture of two substances or more, with different
types that depend on the density of each solute and the solvent.
A solution is a mixture, and there are many different types of mixtures studied in
chemistry. Understanding the definitions of these various types of mixtures is the key to
knowing when to use them. First of all, a mixture is a physical combination of two or more substances where
each substance retains its distinct identity. There are two main types of mixtures: homogeneous mixtures and heterogeneous
mixtures.
A heterogeneous mixture has a nonuniform composition. This oftentimes means that the various substances in the mixture are visible to the
naked eye, such as in an oil and water mixture. The prefix hetero- means different, which indicates that the composition of the
mixture is different throughout.
In contrast, a homogeneous mixture is a mixture with a uniform composition. This means that the components of the mixture are indistinguishable from one another
once they are combined. We could make a homogeneous mixture by completely dissolving salt in water. Homogeneous mixtures are also referred to as solutions. So, we could call our mixture a salt–water solution. We can remember the definition of a homogeneous mixture by recalling that the prefix
homo- means same, indicating that the appearance and composition of the mixture is
the same throughout.
Now that we’ve reviewed the most basic differences between homogeneous and
heterogeneous mixtures, let’s take a look at the answer choices.
We can eliminate answer choices (A) and (B) because we’ve learned that solutions are
homogeneous mixtures, not heterogeneous mixtures. So, our solution is a homogeneous mixture and consists of one or more solutes
dissolved in a solvent. The solvent is the major component and does the dissolving. The solute is the minor component and gets dissolved. The physical state of a solution may be solid, liquid, or gas and depends on the
physical states of the solutes and solvent. However, in most cases, the physical state of the solution depends on the state of
the solvent.
The solute and solvent may have the same physical states. For example, if we dissolved liquid ethanol in liquid water, the solution that forms
would also have a liquid state. However, whenever a solution contains a substance dissolved in water, the aq symbol
is used to tell that the solution is an aqueous solution. In contrast, the solute and solvent may have different physical states. For example, when a solid salt is completely dissolved in liquid water, the solution
that forms has the liquid state, which was the state of the solvent. And once again, because the solute was dissolved in water, the symbol aq must be
used.
So, now we understand that there are different types of solutions that depend on the
physical states of the solutes and the solvent. Therefore, given the remaining answer choices, the most accurate definition of a
solution is answer choice (C). A solution is a homogeneous mixture of two substances or more, with different types
that depend on the physical state of each solute and the solvent.
