1. Copyright © Houghton Mifflin Harcourt Publishing Company What is a solution? A solution is a homogeneous mixture in which two or more substances are so completely blended and evenly distributed that you cannot identify the different parts. A solution may be solid, liquid, or gas. Unit 5 Lesson 1 Solutions

2. What are the two parts of a solution? Solutions have two parts: the solute and the solvent. The solute is the substance that is being dissolved in a solution. A solute can be a liquid, gas, or solid. The solvent is the substance in the solution that does the dissolving. A solvent can also be a liquid, gas, or solid. Water is the most common liquid solvent. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 5 Lesson 1 Solutions

3. Concentrate! Copyright © Houghton Mifflin Harcourt Publishing Company How can the concentration of a solution vary? The measure of the amount of solute dissolved in a solvent is called concentration. One way to calculate the concentration of a solution is to divide the mass of the solute by the volume of the solvent. The units of concentration are often expressed as grams per milliliter (g/ml). Unit 5 Lesson 1 Solutions

4. How can the concentration of a solution vary? A dilute solution contains a small amount of solute in a given volume of solvent. A concentrated solution contains a large amount of solute in a given volume of solvent. A saturated solution contains the most solute that can be completely dissolved in a given amount of a solvent at a given temperature and pressure. If more solute is added to a container of a saturated solution, it will settle to the bottom without dissolving. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 5 Lesson 1 Solutions

5. How can the concentration of a solution vary? Raising the temperature of a saturated solution often allows more solute to dissolve. A supersaturated solution is very unstable. If even a single crystal of solute is added, all the extra solute will quickly solidify, so that it is no longer dissolved in the solution. The result is often the formation of beautiful crystals of the solute. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 5 Lesson 1 Solutions

6. What factors affect solubility? The solubility of a solute is its ability to dissolve in a given amount of solvent at a certain temperature and pressure. An increase in temperature has two effects on most solid solutes—they dissolve more quickly, and a greater amount can be dissolved in a given amount of liquid solvent. The opposite is true for gases—an increase in temperature makes a gas less soluble in water. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 5 Lesson 1 Solutions

7. What factors affect solubility? Pressure changes do not usually change the solubility of solids or liquids. However, the solubility of a gas increases at higher pressures and decreases at lower pressures. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 5 Lesson 1 Solutions

8. What helps solids dissolve faster in liquids? An increase in temperature, an increase in surface area, and an increase in motion can all help a dissolving solid to dissolve more quickly. Heating a mixture can help a solid dissolve very quickly in a liquid. Crushing increases the surface area of solute that is exposed to the liquid solvent. Crushing helps solids dissolve faster. Solids also dissolve faster when you stir or shake a mixture. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 5 Lesson 1 Solutions