1. Chapter 23 Solutions

2. Section 1 How Solutions Form
Solution—a mixture that appears the same throughout and is mixed at the molecular level
1. Solute—substance being dissolved
2. Solvent—substance doing the dissolving

3. 3. Solutions can be liquids, gases, or solids.
4. Alloys are solid solutions.
B. How dissolving happens:
1. Water molecules are polar—they have a positive area and a negative area.

4. 2. Water molecules cluster around solid molecules, with their negative ends attracted to the positive ends of the solids.
3. Water molecules pull the solid particles into solution.
4. The moving water molecules and solid molecules spread out and mix evenly to form a solution.
5. To mix solids to make an alloy solution, you must melt the solids.

5. C. Rate of dissolving depends on:
1. Stirring—speeds up dissolving by bringing more fresh solvent into contact with more solute.
2. Crystal size
Dissolving occurs at the surface of a solid.
b. Breaking a solid into pieces or powder increases its surface area, which speeds up dissolving.

6. 3. Temperature—increasing the temperature of a solvent speeds up the movement of its particles.
4. To make a gas dissolve more quickly in a liquid, cool the liquid solvent and increase the pressure of the gas.

7. Section 2 Dissolving Without Water
Nonpolar materials have no positive or negative areas.
They are not attracted to the polar water molecules, so they do not dissolve easily in water.
2. Example: oils contain hydrocarbons.
Large molecules of carbon and hydrogen atoms
b. These atoms share electrons in an equal manner, so there is not positive or negative charge.

8. B. Useful nonpolar molecules
Nonpolar solvents dissolve nonpolar solutes.
2. Many nonpolar solvents are toxic—dangerous to touch or inhale
3. Soap—used for washing because it has polar and nonpolar properties.

9. C. Polarity and vitamins
B vitamins and vitamin C are polar—dissolve in the water in your body cells.
2. Vitamin A is nonpolar—dissolves in the fat of some body cells.

10. Section 3 Solubility and Concentration
A. Solubility—the amount of a substance that can dissolve in a solvent
Depends on the nature of the substances.
2. Solubilities of two substances can be compared by measuring.

11. B. Concentration
A concentrated solution has a large amount of solute in the solvent.
2. A dilute solution has a small amount of solute in the solvent.
3. Concentrations can be expressed as percent by volume of the solute.

12. C. Types of solutions
1. Saturated solution—contains all the solute it can hold at a given temperature.
As the temperature of a liquid solvent increases, the amount of solid solute that can dissolve in it increases.
b. Solubility curve—line on a graph used to figure how much solute can dissolve at any temperature on the graph

13. 2. Unsaturated solution—able to dissolve more solute at a given temperature
3. Supersaturated solution—contains more solute than a saturated one at the same temperature
Made by raising temperature of a saturated solution, adding more solute, and lowering temperature back without disturbing the solution
b. Unstable—will crystallize if disturbed
c. As it crystallizes, it gives off energy and produces heat.

14. Section 4 Particles in Solution A. Ions—particles with a charge
1. Electrolytes—compounds that form charged particles (ions) and conduct electricity in water
2. Nonelectrolytes—substances that do not ionize in water and cannot conduct electricity
Section 4 Particles in Solution

15. B. How ions form
Ionization—molecules break apart in water, causing atoms to become ions by taking on a charge.
2. Dissociation—an ionic solid separates into its positive and negative ions.

16. C. Effects of solute particles
All solute particles—polar, nonpolar, electrolyte, and nonelectrolyte—affect the physical properties of the solvent.
2. Adding a solute to a solvent lowers the freezing point because the added solute particles interfere with the formation of the orderly freezing pattern.
3. Adding a solute raises the boiling point because fewer solvent molecules can reach the surface and evaporate.