Solutions #12

(grades 6-10)
Soft-bound, 72 page book, 28 reproducible task cards, full teaching notes.

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Begins with corn starch. Mixed cold, it forms a coarse suspension that clears by filtering or settling. When boiled it forms both a cloudy colloidal suspension and a clear true solution. Apply concepts and vocabulary learned here to a series of tasks that clean muddy water: Alum coagulates the clay, chlorination bleaches all traces of food coloring, but only distillation makes it pure. Use common salts to study about crystals, concentration and saturation, rates of dissolving and limits of solubility.

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Solutions Supplies

WE SUPPLY seven key chemicals: 10 mL Alum, 10 mL Copper Sulfate, 20 mL Rock Salt, 20 mL Epsom Salt, 20 mL Calcium Acetate, 20 mL Sodium Thiosulfate and 1 dropper bottle of Iodine. YOU SUPPLY everything else.


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Table of Contents for #12 Solutions:

Preparation and Support

A TOPS Model for Effective Science Teaching • Getting Ready • Gathering Materials • Sequencing Task Cards • Gaining a Whole Perspective• Long Range Objectives • Review/Test Questions

Activities and Lesson Notes

  1. 1. Two Kinds of Filters
  2. 2. Two Ways to Purify
  3. 3. A Matter of Size
  4. 4. Definitions
  5. 5. Clearing Muddy Waters
  6. 6. Coagulation
  7. 7. Purify By Chlorination
  8. 8. Purify By Distillation
  9. 9. Oil and Water
  10. 10. In Between
  11. 11. Alcohol and Water
  12. 12. What Kind of Mixture?
  13. 13. Hot and Cold
  14. 14. Particle Size
  15. 15. Saturation
  16. 16. Can More Dissolve?
  17. 17. Frosted Glass
  18. 18. Basic Shapes
  19. 19. Water Spots
  20. 20. Equilibrium

  22. 21. Rate of Dissolving (1)
  23. 22. Rate of Dissolving (2)
  24. 23. Water of Hydration (1)
  25. 24. Water of Hydration (2)
  26. 25. Solubility Variables
  27. 26. Solubility Curves
  28. 27. Negative Solubility
  29. 28. Supersaturation

Supplementary Pages

cube pattern • equilibrium strip • graph paper


Complete Master List for #12 Solutions:

Key: (1st/2nd/3rd) denote needed quantities: (1st) enough for 1 student doing all activities; (2nd) enough for 30 students working in 10 lab groups all self-paced; (3rd) enough for 30 students working in 10 lab groups, all doing the same lesson. Starred* items may be purchased below.

  1. 1/1/1: roll soft paper towels
  2. 1/10/10: scissors
  3. * 5/50/50: laboratory filters. Some densely-woven lavatory paper towels on rolls may also work. Test in advance.
  4. * 1/1/1: packages: corn starch, granulated sugar, alum, fine-grained table salt, baking soda, copper sulfate, rock salt, Epsom salt. Include a dispensing spoon with each package.
  5. * 3/30/30: baby food jars or equivalent, most with lids (or small beakers)
  6. 1/1/1: water source. Use distilled water if source is hard.
  7. * 1/6/10: dropper bottles each: iodine, rubbing alcohol.
  8. 1/3/6: dropper bottles each: chlorine bleach, mineral oil, liquid detergent, India ink, vinegar, distilled water.
  9. 1/1/1: hot plate with teapot (or Bunsen burner, or alcohol lamps, and matches)
  10. * 2/10/20: eyedroppers

  11. 1/1/2: packets of non-dairy creamer
  12. 1/1/1: shaker of pepper
  13. * 3/30/30: test tubes, 12 mL or more
  14. * 1/5/10: magnifying glasses
  15. 1/10/10: small paper drinking cups
  16. 1/4/10: metric rulers (optional)
  17. * 1/1/1: roll aluminum foil
  18. 1/1/1: package rice
  19. 1/1/1: envelope powdered milk
  20. 1/1/1: package flour, bleached or unbleached

  21. * 1/5/10: rolls clear tape
  22. * 1/10/10: graduated cylinders, 10 mL capacity
  23. 1/1/1: box seltzer tablets, Alka-Seltzer or equivalent
  24. 1/1/1: box sugar cubes
  25. * 1/6/10: microscope slides
  26. 1/1/1: box facial tissues (roll toilet paper)
  27. 1/4/10: microscopes (optional)
  28. * 1/1/1: package rubber bands
  29. 1/1/1: can scouring cleanser (optional)
  30. 1/10/10: index cards

  31. 1/2/4: paper punch tools
  32. * 1/1/1: box plastic straws
  33. 1/1/1: wall clock with second hand (or wristwatches)
  34. * 1/6/10: gram balances (instruments constructed in #05 Weighing are suitable)
  35. 1/10/10: calculators
  36. * 1/5/10: small Pyrex beakers
  37. * 1/1/1: clothespins
  38. 1/1/1: permanent markers
  39. 1/1/1: bottle calcium acetate
  40. 1/1/1: bottle sodium thiosulfate

Convenient Shopping:

Aluminum Foil

regular strength, 20 square feet x 12 inches rolls

Buy aluminum foil here as a convenience item, or for less in many grocery stores.

Baby Food Jars - assorted

without lids

Each set includes 4 small, 4 medium and 4 large glass jars.


50 mL, heat-resistant Pyrex

Needed for #10 Analysis and #12 Solutions.


wooden, spring-action

These are handy lab items to keep in stock. We use them as bulb holders, tongs, clips, and more.

Dropper Bottle with Eyedropper

1/2 ounce, amber glass

Very handy for storing and conveniently dispensing small quantities of liquid. You may also purchase eyedroppers without bottles as item #1120.


glass, with rubber bulbs and screw-on plastic bottle top

These have many lab uses. You may purchase them separately here, or with 1/2 ounce dropper bottles (as item #1121).

Separately, these also double as Cartesian Divers in #200 Diving into Pressure & Buoyancy. If you already have droppers, test them in advance to see if they make good 'divers': Remove plastic bottle top, if any. Dropper must float when empty, then sink with a one-squeeze-intake of water. Test that the seal between bulb and barrel is water tight: The empty dropper should float for a day or so in a glass of water, without taking on visible water.

Filter Paper

lab grade

A handy lab supply, 12.5 cm dia. circles. Lab grade filters are remarkably expensive. Rinse and dry after each use to use again! Hey, TOPS is not rocket science.

Graduated Cylinder - 10 mL

shatter resistant plastic on stable base

An important lab inquiry tool for measuring small liquid volumes.

Gram Pocket Scale

digital, pocket size

Digitally weighs up to 500 grams, plus tare container. Sensitive to 0.1 gram in multiple weight units. Durable, but not childproof. Comes with two AAA batteries to get you started.

Magnifier - hand lens

3X clear plastic hand lens

You'll find many uses for this basic tool of scientific inquiry. Very nice quality for the price. Supports #17 Light, #23 Rocks and Minerals, and #42 Focus Pocus. (One 3X hand lens is also included in each #100 Triple Magnifier Kit.)

Microscope Slides

glass, standard size

Used in #17 Light for diffraction experiments. For viewing microscope specimens, consider cutting slides, almost for free, from clear plastic bakery cartons. Smooth any sharp edges with sandpaper or an emery board.

Rubber Bands - assorted

10 grams each of thin, medium and thick

You get 30 grams of soft, strong, durable rubber bands: thin #16 (about 50), medium #32 (about 20), and heavy-duty #64 (about 10). These sizes are specifically selected to work in most TOPS experiments.

Straws - straight

plastic, thin

Any length straw, between 0.20 and 0.25 inches in diameter is suitable. Grocery stores generally carry straws with flexible "elbows." You can use those if you cut off the bendable section before using.

Tape - clear

3/4 inch x 1000 inch roll

Your standard desk tape with matte write-on surface.

Test Tube - medium disposable

19 mL capacity, 16 mm OD, 5 inch (125 mm) length

A lighter weight rimless Pyrex test tube made with thinner glass.

Test Tube - medium reusable

14 mL capacity, 15 mm OD, 5 inch (125 mm) length

A tough Pyrex test tube made with rim and thicker glass. Has a white spot for labeling.

Teaching Tips for #12 Solutions:

We encourage improvisation - it's one of the main goals of our hands-on approach! You and your students might invent a simpler, sturdier or more accurate system; might ask a better question; might design a better extension. Hooray for ingenuity! When this occurs, we'd love to hear about it and share it with other educators. Please send ideas and photos to

Lesson by Lesson Objectives for #12 Solutions:

  1. Lesson 1: To compare the filtering capacity of soft and hard paper towels. To relate the porosity of filter paper to the size of particles in suspension.
  2. Lesson 2: To clear a suspension by settling and by filtering. To understand how these processes work in nature.
  3. Lesson 3: To relate the clarity of a solution to the size of particles it contains. To examine how saliva breaks down starch into simple sugars.
  4. Lesson 4: To compare and contrast a coarse suspension, colloidal dispersion and true solution. To define and use basic vocabulary.
  5. Lesson 5: To clear a mixture of soil and water by settling and filtration. To observe how soil particles tend to sort by size.
  6. Lesson 6: To coagulate a colloidal clay dispersion in water with aluminum salt so it may be cleared by filtration.
  7. Lesson 7: To treat water with chlorine bleach. To understand that this kills bacteria but fails to remove other dissolved toxins.
  8. Lesson 8: To build a simple solar distillation apparatus that will purify a true solution.
  9. Lesson 9: To understand the role of refracted light in revealing the interface between phases of different densities. To observe how detergent forms an emulsion in oil.
  10. Lesson 10: To understand why salt and water lose volume when mixed together.
  11. Lesson 11: To observe how light bends as alcohol dissolves in water. To explain the reduction in volume as these liquids form a solution.
  12. Lesson 12: To review three purifying techniques studied thus far. To distinguish between coarse suspensions, colloidal dispersions and true solutions.
  13. Lesson 13: To discover how temperature influences the rate of dissolving. To distinguish between heterogeneous and homogeneous mixing.
  14. Lesson 14: To geometrically demonstrate how the surface area of a solute increases as its crystals are subdivided into smaller particles. To understand why pulverizing the solute accelerates its dissolving rate.
  15. Lesson 15: To recognize that solvents have a saturation point beyond which more solute will not readily dissolve.
  16. Lesson 16: To compare the dissolving capacity of saturated salt water with fresh water.
  17. Lesson 17: To examine rapid crystal growth on a microscope slide. To recognize the basic repeating pattern.
  18. Lesson 18: To grow crystals from saturated salt solutions. To identify the basic repeating crystal shapes.
  19. Lesson 19: To analyze various sources of drinking water for the presence of dissolved minerals.
  20. Lesson 20: To model equilibrium conditions in a saturated solution. To appreciate, on a molecular level, the dynamic nature of saturated solutions.
  21. Lesson 21: To graph how rock salt dissolves as a function of time. To observe that the rate of dissolving slows as the solution approaches its point of saturation.
  22. Lesson 22: To become familiar with various units of concentration. To graph, in standard units, how a dissolving salt approaches its limit of solubility as a function of time.
  23. Lesson 23: To test various salts for water of hydration.
  24. Lesson 24: To quantitatively determine how much water of hydration is held by Epsom salt. To compare this experimental value with theoretical values based on its gram formula weight.
  25. Lesson 25: To observe how solubility changes with the nature of the solute and the temperature of the solvent. To describe these changes in both qualitative and quantitative terms.
  26. Lesson 26: To read and interpret a solubility graph. To predict the solubility of salts in water at specific temperatures.
  27. Lesson 27: To recognize that the solubility of some solutes in water decreases with increasing temperature.
  28. Lesson 28: To make a supersaturated solution of sodium thiosulfate that recrystallizes with the addition of a seed crystal to a more stable form. To observe that heat is released as the solution stabilizes.

National Science Education Standards (NRC 1996) for #12 Solutions:

TEACHING Standards

These 28 Task Cards promote excellence in science teaching by these NSES criteria:
Teachers of science...
A: ...plan an inquiry-based science program. (p. 30)
B: and facilitate learning. (p. 32)
C: ...engage in ongoing assessment of their teaching and of student learning. (p. 37)
D: and manage learning environments that provide students with the time, space, and resources needed for learning science. (p. 43)

CONTENT Standards

These 28 Task Cards contain fundamental content as defined by these NSES guidelines (p. 109).
• Represent a central event or phenomenon in the natural world.
• Represent a central scientific idea and organizing principle.
• Have rich explanatory power.
• Guide fruitful investigations.
• Apply to situations and contexts common to everyday experiences.
• Can be linked to meaningful learning experiences.
• Are developmentally appropriate for students at the grade level specified.

Unifying Concepts and Processes

NSES Framework: Systems, order, and organization • Evidence, models and explanation • Constancy, change, and measurement • Evolution and equilibrium • Form and function
Core Concepts/Processes: The diminishing size of dissolved particles determines the nature of suspensions, colloidal dispersions and true solutions.

Science as Inquiry (content standard A)

NSES Framework: Identify questions that can be answered through scientific investigations. • Design and conduct a scientific investigation. • Use appropriate tools and techniques to gather, analyze, and interpret data. • Develop descriptions, explanations, predictions, and models using evidence. • Think critically and logically to connect evidence and explanations. • Recognize and analyze alternative explanations and predictions. • Communicate scientific procedures and explanations. • Use mathematics in all aspects of scientific inquiry.
Core Inquiries: Inquire into the nature of solutions. Evaluate basic techniques for purifying water.

Physical Science (content standard B)

NSES Framework:Properties and changes of properties in matter • Chemical reactions • Interactions of energy and matter
Core Content:Coarse and fine suspensions • Dispersions • True solutions • Saturation • Supersaturation • Equilibrium • Solubility rate • Solubility variables • Water of hydration

Science in Personal and Social Perspectives (content standard F)

NSES Framework: Science and technology in local challenges. Core Content: Apply physical and chemical strategies to water purification.