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The concept of solutions, focusing on solutes and solvents. It discusses the difference between a solvent and a solute, and provides examples of solutions in various states (liquid, solid, and gas). The document also covers the importance of water as a universal solvent and the existence of solid and gas solutions.
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36 Chapter 2 • Solutions NEL
Have you ever made iced tea by mixing a powder and water (Figure 1)? If so, did you use more powder or more water to make the drink? You probably mixed a lot of water with a small amount of powder. What kind of mixture is iced tea? It looks like a pure substance, but you know that it contains at least two components (water and tea). It is a homogeneous mixture, or solution. The powder mixes evenly, or dissolves , into the water to make the solution. Most solutions are made by dissolving a small quantity of one type of matter into a much larger quantity of another type of matter. The part that is present in the larger quantity is called the solvent. The part that is present in the smaller quantity is called the solute. The solutes are the parts of the solution that dissolve. Solutions are generally made by dissolving one or more solutes in a solvent.
You are probably most familiar with solutions that are liquids. These all have liquid solvents. In food preparation, the solvents are usually liquids like water or vegetable oil. In iced tea, water is the solvent. Water is the most common solvent on Earth. Other solvents, besides water, are also useful. Ethanol is the solvent in perfume. Turpentine is a solvent that is used with paints. Ethyl acetate is one of the solvents in nail polish (Figure 2).
The solutes that dissolve in liquids may be solids, liquids, or gases. Salt and sugar are common solid solutes. Acetic acid is a liquid solute that can be added to water to form vinegar. Gases such as carbon dioxide and nitrogen dissolve in our blood and are carried around our bodies. Can you think of other solids, liquids, and gases (solutes) that dissolve in liquids to form solutions?
dissolve: to mix one type of matter into another type of matter to form a solution
solvent: the larger part of a solution; the part of a solution into which the solutes dissolve
solute: the smaller part of a solution; the part of a solution that dissolves in the solvent
Figure 1 (^) This iced tea was made by dissolving iced tea powder in water.
Figure 2 Ethanol, turpentine, and ethyl acetate are useful solvents for matter that does not dissolve in water.
During Reading: Comparisons Comparisons are used to make clear what is the same and what is different about two or more items. As you read this section, compare characteristics of solvents and solutes. How are they similar? How are they different? How does making comparisons help you to better understand solvents and solutes?
L I N K I N G T O L I T E R A C Y
NEL 2.1 Solutes and Solvents 37
The water from your tap probably looks and tastes like pure water. Tap water is a solution that contains many solutes. These solutes include iron, aluminum, salt, fluorine, calcium, magnesium, and chlorine. How did they get into your tap water? As water flows in rivers and lakes and underground, it comes into contact with many types of matter (Figure 3). Gases from the air and minerals from the rocks and soil dissolve in the water. Pollutants may also dissolve in the water.
Before water reaches your tap, it is cleaned to make it safe for drinking. Chlorine and fluorine are sometimes added to the water. Chlorine kills bacteria, and fluorine may help keep your teeth healthy. Water probably dissolves more different substances than any other solvent. For this reason, water is sometimes called “the universal solvent.” Water is the solvent in many important solutions.
Water in Your Body Your body is about 70 % water. All this water dissolves many different solutes, making a variety of solutions. The solutes include salt, oxygen, sugars, and mineral components such as calcium and potassium. These solutes are able to travel around your body because they are dissolved in water. Blood plasma, sweat, urine, and tears are common solutions produced by your body. Water is the solvent in all of these solutions.
Water around Earth About 70 % of Earth’s surface is covered by water. There is always about the same amount of water on Earth. Water from rivers and oceans evaporates into the air and then condenses to form clouds and precipitation (rain and snow). As water moves around Earth, it dissolves many different solutes. These solutes are transported to almost every part of the world. Figure 4 shows that solutes in water can be absorbed by living things.
Figure 4 (^) Plants absorb the minerals and nutrients dissolved in water through their roots.
Figure 3 (^) As water flows in a stream, it dissolves many substances.
To learn more about “the universal solvent,” Go to Nelson ScienceGo to Nelson Science
NEL 2.1 Solutes and Solvents 39
Plants and animals get some of the nutrients they need from water. However, water can dissolve pollutants, too. Pollution includes any pure substance or mixture that contaminates the natural environment. Polluted water is a mixture of pure water and pollutants. Figure 7 shows how pollutants can enter water from various sources. It is very important to keep the water in our lakes, rivers, and oceans clean, so that organisms can grow and live there normally. We all have to be careful not to let contaminants get into our water.
pollution: contaminants in the environment that could harm living things
Figure 7 Sources of water pollution
How will you use the information about solutes and solvents in this section when you start to work on the Unit Task?