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Some lemonade is a mixture of lemon juice, water, and sugar.
You know there’s sugar in lemonade, because the drink tastes sweet—but you can’t see the sugar, because it’s completely dissolved.
If you mix together lemon juice, water, and sugar, they form a solution. That’s a mixture in which the different kinds of matter are spread out evenly. In lemonade, water is called the solvent, and the sugar and lemon juice are solutes. A solute is matter that dissolves in a solvent. The solvent is often a liquid, such as water. If a solution consists of different amounts of two liquids, the solvent is the liquid that occupies the majority of the solution.
▲ One way to make lemonade is by combining lemon juice, water, and sugar.
The Lemony Ticket
Lemonade has properties similar to other solutions.
Once it is completely combined, a solution’s consistency is the same throughout. In the example of lemonade, the ratio of sugar to water to lemon juice is the same everywhere in the container.
◀ Ocean water is a solution of salt and water. There are roughly 2.2 pounds of salt in every cubic foot of ocean water. A cubic foot of water is all the water that would fit in a container one foot high, one foot wide, and one foot deep. If all the salt in the ocean could be spread over the land, it would form a layer about as tall as a 40-story building.
Desalination Plant
▲ Scientists have found ways to use evaporation and other methods to create freshwater from ocean water. The process is called desalination, and it is important in parts of the world where freshwater is hard to find.
Oil
Sand
Pepper
Wood
▲ Sugar and salt form solutions with water easily. But oil, pepper, sand, and wood do not. Why? The answer has to do with the forces that hold the molecules of these materials together. A molecule is the very smallest amount of something. For a solution to form, there must be an attraction between the molecules of the solute and solvent, in this case between water and oil (or sand or pepper or wood). When the attraction is not strong enough, the solvent does not spread out into the water, and no solution forms.
◀ Water can form a solution with air, and that produces humidity. Like other solutions, air can become saturated with water. When that happens, we say that the relative humidity is 100 percent. As the temperature cools down, the air can hold less water, and that leads to rain.
Fog
Mud
▲ Mud puddles and fog are mixtures, but neither one is a solution. Mud puddles and fog are both called suspensions, which are mixtures of bits of matter that are big enough to be visible. A mud puddle is a suspension of soil and water, while fog is a suspension of water droplets in air. The matter in most suspensions can be separated with a filter. But not fog, because it is a kind of suspension called a colloid. Colloids have very tiny particles of matter, so they can’t be filtered easily.
