Chapter 11 Water and Solutions

2 Homework for Chap 11 Read p 275 – 280; Applying the Concepts # 1 – 3;

Fig (A) The water molecule is polar (It has a dipole.) H2OH2O Fig (B) Attractions between water molecules

Ice is less dense than water Water is a Unique Substance: Fig The hexagonal structure of ice

Maximum Density 4 °C Density of Water Fig The density of water just above its freezing point

Solution - a homogenous mixture of 2 or more substances Solute - the substance(s) present in the smaller amount(s) Solvent - the substance present in the larger amount SolutionSolventSolute Soft drink (l) Air (g) Soft Solder (s) H2OH2O N2N2 Pb Sugar, CO 2 O 2, Ar, CH 4 Sn

Fig 11.6 NaCl dissolving in water

Fig Behavior of electrolytes and nonelectrolytes.

Electrolyte - a substance that, when dissolved in water, forms a solution that can conduct electricity. Nonelectrolyte - a substance that, when dissolved, forms a solution that does not conduct electricity. nonelectrolyte strong electrolyte

Fig The reaction of water and hydrogen chloride Hydronium ion

Acids, Bases, and Salts acid + base salt + water HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O

12 Acids 1.Have a sour taste. e.g., Vinegar, lemons, limes, sour milk 2.Cause litmus to change from blue to red. 4. Acid solutions conduct electricity. 3. Acids neutralize bases. Fig (A)

13 1. Have a bitter taste. e.g., caffeine, walnuts, soap 3. Feel slippery. Many soaps contain bases. Bases 5. Basic solutions conduct electricity. 2. Cause litmus to change from red to blue. 4. Bases neutralize acids. Fig (B)

14 How do we express the concentration of an acid or a base? pH scale – based on concentration of the hydronium ion (H 3 O + ) acidicbasicneutral Based on powers of 10: e.g., a soln with pH = 3 is 10 times more acidic than a solution with pH = 4

Fig Common substances that are acidic

Table 11.5 Approximate pH of some common substances