11.1 What is a solution

We use the word solution to describe a homogenous mixture. If you recall your earlier knowledge of chemistry, a homogenous mixture is a mixture that has the same concentration throughout. Let’s look at the simplest form of a homogenous mixture that we see or frequently prepare at home, sugar and water solution. We dissolve sugar in water to prepare a sugar solution. The chemical formula of sugar is C₁₂H₂₂O_11, also known as sucrose. In preparing this solution, we stir sugar in water because we try to disperse sugar molecules evenly in water. You can describe this process by the following reaction.

C₁₂H₂₂O₁₁(s)                                C₁₂H₂₂O₁₁(aq)  Eq. 11.1

Here (s) indicates solid, and (aq) indicates aqueous, meaning sugar molecules are dissolved in water. A solution forms when solute and solvent are mixed together to make a homogenous mixture. The word solute is used for the compound that is being dissolved, and solvent is used to describe the medium in which we dissolve. In the example above, sugar is the solute, and the solvent is water.

Watch this video to see the formation of sugar or salt solution.

Download this Phet simulation first; then, by clicking on the link, you will be able to access the simulation

https://phet.colorado.edu/en/simulation/legacy/sugar-and-salt-solutions

Fig. 11.1

Source: https://Phet.colorado.edu

Usually, a solute is in a smaller quantity, and the solvent is in a larger amount. Solute and solvent do not always need to be solid and liquid; they can be in any state of matter. However, the state of the solution will be the same as the state of the solvent. Here are a few examples of different types of solutions made up of different states of matter.

Table 11.1

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Learning Check: 

1. Identify the solute and solvent in a hydrogen peroxide solution used in cleaning small wounds at home.
2. Which of the following is/are not a solution?
3. Tap water              b) Water at sea beach             c) Helium in party balloon

Answer: 1) Solute is hydrogen peroxide, and water is solvent,

2) b) Water at sea beach is not a solution; it is a heterogeneous mixture of salt, sand and other particles in water.  If you take this water in a bucket you can see lot of sand, small plants and sometimes even few sea shells and other particles floating or sitting in the bucket, that’s why it is a heterogenous mixture and not a solution.   

c) Helium in a party balloon is an element, not a solution

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