Chapter 13 Ions in Aqueous Solutions and Colligative
Properties
Chapter Opener
__Chapter Overview, TE Review the objectives listed in the Student Edition.
Section 1 Compounds in Aqueous Solutions
PACING: 90 minutes
PENNSYLVANIA ACADEMIC STANDARDS FOR SCIENCE AND TECHNOLOGY:
3.2.A.2 Know that science uses both direct and indirect observation means to study the world and the universe;
3.2.B.1 Describe materials using precise quantitative and qualitative skills based on observations;
3.2.B.2 Develop appropriate scientific experiments: raising questions, formulating hypotheses, testing, controlled
experiments, recognizing variables, manipulating variables, interpreting data, and producing solutions;
3.2.B.3 Use process skills to make inferences and predictions using collected information and to communicate, using
space / time relationships, defining operationally;
3.2.C.2 Evaluate the appropriateness of questions;
3.2.C.4 Conduct a multiple step experiment;
3.2.C.5 Organize experimental information using a variety of analytic methods;
3.2.C.6 Judge the significance of experimental information in answering the question.
Objectives
1. Write equations for the dissolution of soluble ionic compounds in water.
2. Predict whether a precipitate will form when solutions of soluble ionic compounds are combined, and
write net ionic equations for precipitation reactions.
3. Compare dissociation of ionic compounds with ionization of molecular compounds.
4. Draw the structure of the hydronium ion, and explain why it is used to represent the hydrogen ion in
solution.
5. Distinguish between strong electrolytes and weak electrolytes.
FOCUS (5 minutes)
__ Lesson Starter, TE Ask students to compare the composition and arrangement of a colored crystalline
salt with an aqueous solution of the same salt
MOTIVATE (10 minutes)
__Demonstration, A Precipitation Reaction, TE Demonstrate precipitation by combining SrCl2•6H2O,
Na2SO4, and water, then have the students note the precipitate that forms, use a solubility table to
identify the precipitate, and write the net ionic equation.
TEACH (65 minutes)
__PowerPoint
__Sample Problem A, SE Demonstrate how to calculate moles of ions produced in dissociation.
__Practice Problems A, SE Students calculate moles of ions produced in dissociation.
__Visual Strategy, Figure 2, TE Have students find the guidelines in Table 1, General Solubility
Guidelines, that apply to the compounds in this figure.
__Table Strategy, Figure 1, General Solubility Guidelines, TE Emphasize that no ionic compound is
entirely insoluble in water. (ADVANCED STUDENTS)
__Sample Problem B, SE Demonstrate how to identify precipitates that form when solutions are
combined.
__Practice Problems B, SE Students identify precipitates that form when solutions are combined.
__Visual Strategy, Figure 4, TE Be sure students are not confused by the apparent conflict between the
equation that uses H+ and this figure that uses H3O+.
__Visual Strategy, Figure 4, TE Have students look back to Table 1, General Solubility Guidelines, to
name another compound that is insoluble but, like AgCl, considered to be a strong electrolyte.
(ADVANCED STUDENTS)
__Historical Chemistry, The Riddle of Electrolysis, SE Several scientists contributed to the discovery
of electrolysis.
__Application, The Riddle of Electrolysis, TE Many common products are made using electrolysis,
including gold- and silver-plated jewelry and keys.
__Discussion, TE Ask students to explain why electrolysis might be used to coat a sheet of iron with
another metal, such as zinc
__Chapter Lab, Microlab, Testing Water for Ions, SE Observe reactions of ions in aqueous solutions,
then test unknown solutions for the presence of ions.
__Datasheet for In-Text Lab, Testing Water for Ions, ANC Students use the datasheet to complete the
Chapter Lab.
__Microscale Experiment, Reacting Ionic Species in Aqueous Solution, ANC
__Microscale Experiment, Colored Precipitates, ANC (ADVANCED STUDENTS)
__Forensic and Applied Science Experiments: Solubility and Chemical Fertilizers Students will
gather and graph temperature-solubility data to explore the effect of temperature on the solubility of a
substance.
CLOSE (10 minutes)
__Section Review, SE Students answer end-of-section vocabulary, key ideas, critical thinking, and
interpreting graphics questions.
OTHER RESOURCE OPTIONS
__Study Guide, Section Review
__Section Quiz
__Additional Sample Problems, TE Demonstrate how to calculate moles of ions produced in
dissociation and how to write net ionic equations for reactions.
__Additional Practice Problems, EXT Students can practice more problems that ask them to calculate
moles of ions produced in dissociation and identify precipitates that form when solutions are
combined.
__Additional Example Problems, TE Demonstrate how to reduce a net ionic equation to its net form by
eliminating spectator ions.
Section 2 Colligative Properties of Solutions
PACING: 90 minutes
PENNSYLVANIA ACADEMIC STANDARDS FOR SCIENCE AND TECHNOLOGY:
3.1.E.1 Describe how fundamental science and technology concepts are used to solve practical problems.
Objectives
1. List four colligative properties, and explain why they are classified as colligative properties.
2. Calculate freezing-point depression, boiling-point elevation, and solution molality of nonelectrolyte
solutions.
3. Calculate the expected changes in freezing point and boiling point of an electrolyte solution.
4. Discuss causes of the differences between expected and experimentally observed colligative properties
of electrolyte solutions.
FOCUS (5 minutes)
__ Lesson Starter, TE Demonstrate that NaCl lowers the freezing point of water by filling two
containers with ice and adding rock salt to one of them.
MOTIVATE (10 minutes)
__Demonstration, The Process of Osmosis, TE Demonstrate osmosis by using sucrose, water, and
dialysis tubing.
TEACH (65 minutes)
__PowerPoint
__Visual Strategy, Figure 6, TE Have students interpret the graph to tell how the solution curve differs
from the normal curve of water and how the boiling and freezing points have changed.
__ Problem Solving Workbook, Chapter 17, ANC Students study sample problems and practice
problems involving colligative properties. (ADVANCED STUDENTS)
__Visual Strategy, Figure 7, TE Emphasize that, in order for the vapor pressure of pure water to be
compared with that of an aqueous solution, the temperatures of both must be identical.
__Table Strategy, Table 2, Molal Freezing-Point and Boiling-Point Constants, TE Ask students
which solvents have the greatest freezing-point depression constants.
__Sample Problem C, SE Demonstrate how to calculate the freezing-point depression
__Practice Problems C, SE Students calculate the freezing-point depression.
__Sample Problem D, SE Demonstrate how to calculate the molal concentration of solution.
__Application, TE Ethylene glycol solution, a common antifreeze, lowers the freezing point of the liquid
in a car radiator. It also serves as a coolant by raising the boiling point.
__Sample Problem E, SE Demonstrate how to calculate the boiling-point elevation.
__Practice Problems E, SE Students calculate the boiling-point elevation.
__Visual Strategy, Figure 8, TE Make sure students understand why osmosis stops and the concept of
reverse osmosis.
__Discussion, TE Ask students to explain osmosis using a mental model based on a theoretical model of
how semipermeable membranes work.
__Chemistry in Action, Water Purification by Reverse Osmosis, SE Osmosis can be reversed when
the pressure applied is greater than the osmotic pressure to an aqueous solution.
__Visual Strategy, Figure 9, TE Ask students to use the figure to explain why calcium chloride is often
used instead of sodium chloride to melt snow and ice from slick roads and sidewalks.
__Sample Problem F, SE Demonstrate how to calculate the expected change in the freezing-point
depression.
__Practice Problems F, SE Students calculate the expected change in freezing-point depression.
__Table Strategy, Table 3, Molal Freezing-Point Depressions for Aqueous Solutions of Ionic
Solutes, TE Make sure students understand that the expected values of the observed Δf divided by the
nonelectrolyte solution Δf would be 2 for KCl and MgSO4 and 3 for BaCl2, according to the
calculations based on number of particles in solution.
__Math Tutor, Determining Boiling and Freezing Points of Solutions, SE Students determine the
boiling and freezing points of solutions.
__Forensic and Applied Science Experiments: Diffusion and Cell Membranes Students use changes
in an egg's mass to study the process of diffusion through a cell membrane.
CLOSE (10 minutes)
__Section Review, SE Students answer end-of-section vocabulary, key ideas, critical thinking, and
interpreting graphics questions.
__Alternative Assessment, TE Have students do an experiment to determine the concentration of salt
required to prevent 500 mL of an aqueous solution from freezing when placed in their home freezer
overnight. (ADVANCED STUDENTS)
OTHER RESOURCE OPTIONS
__Study Guide, Section Review
__Section Quiz
__Additional Sample Problems, TE Demonstrate how to calculate the freezing-point depression, the
boiling-point elevation, and the change in boiling-point elevation.
__Additional Practice Problems, EXT Students can practice more problems that ask them to calculate
the freezing-point depression and the boiling-point elevation for electrolyte solutions.
End of Chapter Review and Assessment
PACING: 45 minutes
__Chapter Review, SE Students answer questions organized by section and as a mixed review.
__Chapter Test A, Ions in Aqueous Solutions and Colligative Properties, ANC Assign questions for
general level chapter assessment.
OTHER RESOURCE OPTIONS
__Standardized Test Prep, SE Have students complete the standardized test prep to help them prepare
for standardized tests.
__SciLinks Visit www.scilinks.org, maintained by the National Science Teachers Association, for
information on Precipitation Reactions, Hydronium Ion, Electrolysis, and Osmosis.
__CNN Video, CNN Presents Science in the News: Chemistry Connections Segment 24, Mixing Oil
and Water: Surfactants