Summer Research Program for Science Teachers

Youning Wang

Murry Bergtraum High School

2002

The Nature Of Dissolving Processes

Time Allocation: Thirty-five minutes.

Performance Objectives: After completing this lesson, students should be able to

1. define solution, solute, solvent, solubility, miscible, and immiscible;

2. describe solubility models on molecular liquids, ionic solids, and molecular solids;

3. understand the rule of "like dissolves like" and the relationship between molecular structures and dissolving properties;

Do Now: List three dissolving processes in your daily life.

(Answer: open-ended, any reasonable answers are acceptable.)

Materials for Demonstration:

· Safety goggles

· 15 small beakers

· Graduated cylinder

· 200 mL of tap water

· 200 mL of octane (gasoline)

· 50 mL each of the following solute solutions: corn oil, vinegar, acetone, ethanol, methanol, sodium chloride, and 0.1 M potassium hydroxide. (Caution: acetone, octane, ethanol, and methanol are flammable.)

Instructional Procedure:

1. Measure 20 mL solutions of corn oil, vinegar, octane, acetone, ethanol, methanol,

    sodium chloride, and potassium hydroxide into eight beakers.

2. Have students predict which solutions are immiscible with water.

3. Add 20 mL water into each beaker (total eight beakers).

4. Have students record the mixture results.

5. Measure 20 mL solutions of corn oil, vinegar, acetone, ethanol, methanol, sodium

    chloride, and potassium hydroxide into seven beakers.

6. Have students predict which solutions are miscible with gasoline.

7. Add 20 mL octane into each beaker (total seven beakers).

8. Have students record the mixture results.

9. Explain the properties of two solvents (water and gasoline) and other seven solutions.

10. Ask students to account for the explanation on demonstration results.

Learning Outcomes:

1.   Fill in following chart with es or o in which using water as a solvent to dissolve other eight kinds of solute solutions.

2.   Fill in following chart with es or o in which using octane as a solvent to dissolve other seven kinds of solute solutions.

Pivotal Questions:

1. (Showing the combination of gasoline and sodium chloride solution, and ask)

   "Why is sodium chloride (a ionic compound) not dissolved in gasoline?"

----Gasoline is a non-polar molecule.

2. (Analyzing the class demonstration, and ask)

   "What is the conclusion that could be drawn from today class demonstration?"

----According to the rule of "like dissolves like", miscible liquids dissolve in each other, in which they must be either all polar molecules or all non-polar molecules.

Homework for Assessment:

Take out six substances from your kitchen cabinet, using water as a polar solvent, to classify those substances into polar compounds and non-polar compounds.

(Presenting your investigation results to the class tomorrow).

REFERENCE TO SCIENCE STANDARDS

            This Lesson Plan aligns with following Science Teaching Standards on the National Science Education Standards (National Academy Press, 2001):

Standard A ---- Plan an inquiry ased science program.

· Select science content and adapt and design a curriculum to meet the interests, knowledge, understanding, abilities, and experiences of students.

· Select teaching and assessment strategies that support the development of student understanding and nature a community of science learners.

Standard B ---- Guide and facilitate learning.

· Focus and support inquiries while interacting with students.

· Encourage and model the skills of scientific inquiry, curiosity and openness to new ideas and skepticism that characterize science.

Standard C ---- Engage in ongoing assessment of teaching and student learning.

· Analyze assessment data to guide teaching.

· Guide students in self-assessment.

Standard D ---- Design and manage learning environments that provide students with the time, space, and resources needed for learning science.

· Create a setting for student work that is flexible and supportive of science inquiry.

· Identify and use resources outside the school.

Standard E ---- Develop communities of science learners that reflect the intellectual rigor of scientific inquiry and the attitudes and social values conducive to science learning.

· Display and demand respect for diverse ideas, skills, and experiences of students.

· Model and emphasize the skills, attitude, and values of scientific inquiry.

Standard F ---- Participate in the ongoing planning and development of the school science program.

· Plan and develop the school science program.

· Participate in decisions concerning the allocation of time and other resources to the science program.

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