What is a Solvent?
What do cola, a brass saxophone, and a filled tooth cavity have in common? They are all examples of solutions containing solvents. A solution is a homogeneous mixture. This simply means the components are uniformly mixed together. For example, your first sip of coffee is the same consistency as your final sip. A solution is made up of a solute, which is the substance being dissolved, and a solvent, the substance in the largest amount into which the solute is dissolved.
Wow, that is a lot of sol- words. I often have a hard time remembering which one is which. Here is one way I remember.
If we write:
Solute + Solvent = Solution
We can see the solution is on the right side of the equals sign. A solution is a similar word for answer, and the answer is always on the right side of an equal side. So, we know that the solution is the solute and solvent added together.
Let's now focus on the solute and solvent. We can remove the sol because it doesn't help us, and we are left with ute and vent. Ute is almost like the word cute, and many cute things are small: cute kittens, puppies, and baby rabbits. Solute is in the smallest amount, and it is the one being dissolved. The other word is vent. When you vent your anger it is normally done in a big way. Solvent is in the largest amount. This is the one doing the dissolving.
Examples of Solvents
One solution we are very used to is dissolving a small amount of solid sugar into our large cup of liquid coffee. Here, the sugar is the solute and the coffee is the solvent. It is true that many solutes are solid and that many solvents are liquid. There are plenty of examples of both solvents and solutes where they are gases, liquids, and solids.
This table shows some examples:
|Solution||Phase of Solution||Phase of Solute||Phase of Solvent|
|Gin and tonic||liquid||liquid (gin)||liquid (flavored water)|
|Brass||solid||solid (Zinc)||solid (Copper)|
|Soda||liquid||gas (CO2)||liquid (flavored water)|
|Seawater||liquid||solid (salt)||liquid (water)|
|Filled tooth||solid||liquid (mercury)||solid (silver and tin)|
Here, we have different solutions of air, gin and tonic, brass, soda, seawater, and a filled tooth. The phase of each component is also shown. Let us now return to our examples from the beginning of the lesson.
First, look at soda. Here we have CO2 gas solute being dissolved in a large amount of flavored water solvent. Our saxophone is made of brass, and it is an example of solid zinc being dissolved in a large amount of copper solvent. The final example is the filled tooth. This consists of liquid mercury being dissolved into solid solvent of silver and tin. In each case, the solvent is always the substance in excess, and the solute is the substance in the smallest amount. Together they form a solution.
Water is a very common solvent. Solutions with water as the solvent are called aqueous solutions. Aqueous solutions are very important in nature and biology. Water is all around us and is called the universal solvent. This is because many, many different solutes dissolve in it.
Not everything dissolves in water though, so let us think briefly about that.
Like Dissolves Like
From experience, we know that sugar dissolves well in coffee, but oil and water do not mix. Try as you might, no amount of shaking will force them to mix and stay mixed. They are both liquids, they seem similar, so why won't they form a solution?
To help explain, let's imagine you and your friends are all fans of the same heavy rock band. You hang out a lot together because you have very similar interests. We can say your group is held together by your love of heavy metal. It's Friday night, and you and your friends are going to visit two places.
Your first visit is to an opera house. Its full of opera fans. What do you think will happen there? You and your friends know very little about opera, and the opera fans know very little about heavy metal. There is no attraction between you and them. If you try and mix with them, it doesn't last long because you are so different. You end up in a separate group on your own. Your group is like the oil, and the opera fans are like the water. You do not mix; you are too different.
You make a quick escape, and next you arrive at a nightclub. This time, it is full of heavy metal fans. They aren't fans of the exact same band as you, but it is very similar. You have a lot in common and you are attracted to each other. Your group is happy to split up and mix with the other heavy metal fans. After a while, you are completely mixed in. Your group is like the sugar, and the heavy metal fans are like the coffee. You mix well; you are very alike. You are a solution of heavy metal fans.
This same thing happens for all solutions. During the mixing or dissolving process, forces holding together the solute particles and forces holding together the solvent particles must be overcome. As a solution forms, new attractions are made between the particles of solvent and the particles of solute. These new attractions must be of a similar strength as the forces originally holding them together. If not, a solution will not form, and the solute does not dissolve in that solvent. We call this behavior 'like dissolves like.' Similar types of solutes will dissolve in similar types of solvents.
So, let's recap what we have learned. A solution is a homogeneous mixture containing a solvent (the substance in the greatest amount doing the dissolving) and a solute (the substance in the smallest amount being dissolved). While it is true that many solutes are solids and many solvents are liquids, other phases are possible, too. Solutes, solvents, and solutions can all be solids, liquids, or gases.
A very important solvent in nature and biology is water. Aqueous solutions are solutions containing water as the solvent. Many solutes can dissolve in water, and that is why water is the universal solvent.
When a solution is formed, forces between particles in the solute and in the solvent are overcome. At the same time, new attractive forces are formed. The forces that are formed in a solution must be a similar strength as the forces overcome in the solute and solvent. We call this behavior 'like dissolves like.' It is good to remember that similar types of solutes will dissolve in similar types of solvents.
- Solution: a homogeneous mixture made of a solvent and a solute
- Solvent: the substance being dissolved
- Solute: the substance doing the dissolving
- Aqueous solutions: solutions with water serving as the solvent
Each part of this lesson on solvents is designed to prepare you to:
- Paraphrase the definition of a solution
- Name the two parts of a solution
- Offer examples of solvents
- Interpret the concept of 'like dissolves like'
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In this activity, students will be applying what they've learned about solvents to identify the components of solutions in their everyday life. For example, students might see Kool-aid in the fridge and identify water as the solvent and the Kool-aid powder as the solute.
In this activity, you'll be looking for solutions in your everyday life to identify solutes. To complete the activity, find 10 different solutions and record them in the table below. Then, identify the solute and the solvent in each solution. The first one has been done for you as an example.
- Which solutions did you find that were aqueous? Were these solutions more or less common in your analysis?
- How were you able to identify the solvent in each solution?
- Why do you think it is important to understand solutions?
Students should be able to identify that any solution that has water as a solvent is an aqueous solution. Since water is a universal solvent, these solutions should be common in their analysis of solutions in their home. The solvent is the substance that is in a greater quantity in the solution. Solutions are important because clearly, they make up so many substances in our lives, and even inside our bodies. Much of our internal composition is made of aqueous solutions and, thus, understanding solutions helps us understand our bodies.
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