How Does Temperature Affect the Amount of Solute Needed to Prepare a Saturated Solution?

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Author: Janice VanCleave

What Effect Does Temperature Have on the Amount of Solute Needed to Prepare a Saturated Solution?

Category: Chemistry—Physical Changes

Project Idea by: Annie Frey

A solution is a homogeneous mixture (a mixture that is the same throughout) of two or more substances. The two types of substances making up a solution are called a solute and a solvent. The substance being dissolved (separated into parts and spread throughout) is called the solute, and the substance doing the dissolving is called the solvent. A solution can exist in any state of matter. The substance present in the smaller amount is usually considered the solute. Solutions in which water is the solvent are called aqueous solutions and are the most common kind of solutions.

The strength of a solution is referred to as its concentration (the amount of solute in a specific amount of solvent). The more solute that is dissolved in a solvent, the greater the concentration of the solution. For example, in a glass of water, the more instant tea added to the water, the greater the concentration of tea in the solution. A glass of tea with a small amount of tea in it is said to be dilute (has a low concentration) in comparison to the more concentrated solution with more tea. If the solute has a color, the darker the color, the more concentrated the solution.

There is a limit to the amount of solute that will dissolve in a given amount of solvent. For example, when you add sugar to a glass of iced tea, it is a waste to keep adding the sugar once it starts settling to the bottom of the glass. No matter how much you stir, the extra sugar will not dissolve. When no more sugar will dissolve in the tea, a saturated solution is produced. A saturated solution is one in which the maximum amount of solute is dissolved in a solvent at a given temperature (a measure of how hot or cold a material is). When less than the maximum amount of solute is dissolved, the mixture is called an unsaturated solution. A project question might be, "What effect does temperature have on the amount of solute needed to prepare a saturated solution?"

Clues for Your Investigation

Use one solute, such as salt, sugar, or Epsom salts, and distilled water for the solvent. Keep the amount of water the same for each test. To vary the temperature, the water can be chilled in the refrigerator and warmed in the sun. CAUTION: Hot water from a faucet or prepared on the stove should be tested only with adult assistance. Do not prepare hot water in a microwave because it can get too hot and erupt when the solute is added.

For each test, add measured amounts of the solute to water. Add the solute a small amount at a time, stirring until the solute dissolves before adding more. When no more solute will dissolve and the solute begins to collect on the bottom of the container, record the amount of solute added as the amount needed to produce a saturated solution in the amount of water used. Compare the amounts of solute needed to make saturated solutions at different temperatures.

Independent Variable: Temperature of the solvent

Dependent Variable: Amount of solute

Controlled Variables: Type of solute, amount of water used, method of measuring solutes, method of stirring

Control: Water at room temperature

Other Questions to Explore

  1. What effect does the type of solute have on preparing a saturated solution?
  2. What is a supersaturated solution? What effect does the type of solute have on preparing a supersaturated solution?
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