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Freezing Point and Point Changes for and

Lesson Plans and Labs

By Ranald Bleakley Physics and Chemistry teacher Weedsport Jnr/Snr High School

RET 2 Cornell Center for Materials Research Summer 2005

Freezing Point and Boiling Point Changes for Solutions and Solids Lesson Plans and Labs

Summary:

Major skills taught: • Predicting changes in freezing and boiling points of , given type and quantity of solute added.

• Solving word problems for changes to boiling points and freezing points of solutions based upon data supplied.

• Application of theory to real samples in lab to collect and analyze data. Students will describe the importance to industry of the depression of points in solids such as and .

• Students will describe and discuss the evolution of making through the ages and its influence on social evolution.

Appropriate grade and level: The following lesson plans and labs are intended for instruction of juniors or seniors enrolled in introductory chemistry and/or physics classes. It is most appropriately taught to students who have a basic understanding of the properties of and of solutions. Mathematical calculations are intentionally kept to a minimum in this unit and focus is placed on concepts. The overall intent of the unit is to clarify the relationship between changes to the composition of a mixture and the subsequent changes in the eutectic properties of that mixture.

Theme: The lesson plans and labs contained in this unit seek to teach and illustrate the concepts associated with the eutectic of both solutions, and glasses

The following people have been of great assistance:

Professor Louis Hand Professor of Physics. 323 Clark Hall Cornell University Ithaca, New York 14853 Phone: (607) 255-6023 Email: [email protected] ... www.physics.cornell.edu/profpages/Hand.html - Aug 2, 2005

David P Wise Staff. Chemistry and Chemical Biology. Clark Hall, Cornell University, Ithaca, New York 14853 ph.(607)255-3674 E-mail [email protected]

Ronald C Kemp staff Cornell Center for Materials Research Clark Hall, Cornell University, Ithaca, New York 14853 ph(607)255-2367 E-mail: [email protected]

John P. Sinnott Staff Cornell Center for Materials Research Clark Hall, Cornell University, Ithaca, New York 14853 ph (607)255-3371 E-mail: [email protected]

Internet Resources:

The following web sites have provided excellent information. 1. Melting and ranges http://www.lib.umich.edu/dentlib/Dental_tables/Melttemps.html

2. http://users.ticnet.com/mikefirth/techspec.htm

3. www.kimble-kontes.com/pdfs/physical_properties_glass.pdf

4. For information about warm glass techniques such as fusing, and kiln forming, visit the Warm Glass website at http://www.warmglass.com

Some preliminary notes for Teachers:

1. The following lesson plans and labs are intended to be taught in class periods of forty-five minutes.

2. Bunsen burners in most labs will not reach high enough temperatures to melt silica sand. Either and additional supply of must be added through regulators or another hotter burning must be used. Temperatures of 9000C to 12000C are needed. /oxygen welding kits are available through many hardware stores at reasonable prices and will safely do the job. NOTE that the glaze on glazed porcelain will melt at these temperatures. Use aluminel crucibles. These are available from Fisher /scientific or Flinn /Scientific.

3. Most glass recipes call for oxide (a.k.a. Sodium Monoxide) Na2O as the primary fluxing agent. This substance carries a warning for inhalation hazard and should be handled with care. Students should either work in fume hoods, or wear good quality dust masks while handling the compound.

4. dioxide (SiO20, silica, or silica sand) can be bought in very fine granulations. These must be handled carefully as they also carry an inhalation risk. Prolonged exposure or large acute doses could to silicosis.

5. Teachers who have furnaces available to them should consider having the students fuse their glass making materials in the furnace. Glassification will occur at temperatures above 9500F for a period of four hours

6. The freezing point and boiling point of water lab is designed to be taught either in two forty minute labs sessions or one double period. Allow plenty of time.

Regents Chemistry Lesson Plan

Teacher: R. Bleakley. Date: / /

Topic: Unit 6 Plan 5 Freezing Point/ Depression. Boiling point elevation.

Objectives: 1) Students will predict changes in freezing and boiling points of water, given type and quantity of solute added. (Standards: 4-5)

2) Students will calculate changes to boiling points and freezing points of solutions based upon data supplied. (Standards: 4-3)

3) Students will apply eutectic theory to real samples in lab to collect and analyze data. (Standards: 4-3)

Materials and Setup: Two large demonstration beakers of boiling water on hot plates Two large demonstration beakers of ice/water mix (NaCl) phosphate (Ca3 PO4)2 Four

Safety: Students close to front should wear safety goggles. Use protective gloves to handle hot beakers All electrical equipment must be supplied from GFCI outlets.

Anticipatory set: 1. (3 minutes) Bring both beakers of water to the boil. Ask students to predict what will happen to one beaker when NaCl is added and to the other when (Ca3 PO4)2 is added. Have them discuss their predictions briefly. Add salts and measure changes. 2. (3 minutes) Have students predict the new boiling temperatures of the two solutions. Bring the solutions back to boiling and record the temperatures. Have students predict the changes to the temperatures of the ice water mixtures with the addition of the two chemicals.

Instruction: • (5 min) Instruct elevation of boiling point and depression of freezing point. • (2 min) Give accepted values for molar boiling point elevation and freezing point depression for water. • (15 min) Demonstrate typical word problems and the methods for their . • (10 min) Instruct real world applications of this information. a. Ice melting on highways b. Ice cream making c. Increased cooking temperature for salted solutions d. Fluxing of metals during alloying

Homework: Assign a selection of representative calculations

Assessment: • Homework will be collected and graded • A quiz will be given prior to the unit exam • A unit exam will include similar problems to the homework set • Class discussions.

Possible Modifications: • The formal quiz could be replaced by an essay or other project tailored to a student’s specific needs. • Out-of-school homework could be substituted with in-school group activities which could take the form of a brief presentation to the class for assessment. • Calculations are often more beneficial to “math challenged” students when the option to work in cooperative groups rather than having to work unsupported and alone.

Note: Accepted values for molal freezing point depression and boiling point elevation for water, as given in Reference tables

THE UNIVERSITY OF THE STATE OF NEW YORK • THE STATE EDUCATION DEPARTMENT • ALBANY, NY 12234 Reference Tables for Physical Setting/CHEMISTRY 2002 Edition

Regents Chemistry Lab. Name: ………………………………...

Freezing Point Depression/ Boiling Point Elevation of Water

Purpose 1. To demonstrate and quantify the changes to the freezing and boiling points of water with the addition of dissolved ions.

Materials Ring stand Utility clamp stirring rod 250 Ml beaker 4 cups

Reagents Distilled water NaCl (sodium chloride) Ice Ca3(PO4)2 (Calcium phosphate)

Safety Wear safety goggles at all times while heating solutions.

Procedure Part I

1. Number your cups 1,2,3,4, then add 5.0g of NaCl to each cup. 2. Fill a 250 ml beaker 2/3 full with crushed ice, then add water to same level. Stir with a stirring rod. 3. Clamp a thermometer into a beaker and record the initial temperature of the ice water. Record temp on the data table below to the nearest 0.5o C. 4. Add the 5.0g of NaCl from cup 1 to the ice-water mixture. Stir and record the temp to the nearest 0.50 C. 5. Next add the 5.0g of NaCl from cup 2 to the ice-water- mixture. Stir and record the temp. 6. Repeat step 4 with the salt from cups 3 and 4.

Part 2. Comparison of two solutes.

1. Repeat the above procedure with Calcium phosphate instead of sodium chloride, and record the data on data table 2.

Data:

Table 1: Effect of sodium chloride on Melting point of ice.

Temp of solution Grams of NaCl added 0.0g 0C

5.0g 0C

10.0g 0C

15.0g 0C

Table 2: Effect of Calcium phosphate on Melting point of ice.

Temp of solution

Grams of Ca3(PO4)2 added 0.0g 0C

5.0g 0C

10.0g 0C

15.0g 0C

Graphing:

On one sheet of graph paper make plots of the temperature of the solution against the grams of solute added. Choose the appropriate axis for the dependant and the independent variables. Use lines-of-best-fit to connect your data points.

Questions:

1. What effect did salt have on the freezing point of water?

2. Use your graph to predict the melting temperature of ice when 30g of NaCl are added, and when 30g of Ca3 (PO4)2 are added

3. What effect would the addition of these salts have on the boiling point of the water?

4. Why is salt added to roads in winter?

5. Why is automobile antifreeze also called coolant? It’s the same stuff, usually glycol.

6. If we repeated the procedure using CaCl 2, how would the results compare?

7. How many ions does Calcium phosphate (Ca3 (PO4)2 ) form in solution and what are those ions. (list them)

8. If we repeated this procedure using sucrose, C6H12O6, how would the results compare?

Part 111.

1. Add 200ml of distilled water to each of four 250ml beakers and number them 1 through 4. 2. Add NOTHING to beaker #1, but bring it to the boil and record its boiling temperature on the table below. 3. Add 5.0g of sodium chloride to beaker # 2, bring it to boiling and record its temperature. 4. Repeat step 3 with 10.0g of salt in beaker 3 and again with 15.0g in beaker #4.

Data:

Boiling Temp Grams of NaCl added 0.0g 0C

5.0g 0C

10.0g 0C

15.0g 0C

Questions:

1. How does the number of dissolved ions in solution affect the boiling point of that solution?

2. Plot your data on graph paper and submit with your lab. What is the relationship between the number of moles of ions in solution and the boiling point.

Regents Chemistry Lesson Plan

Teacher: R. Bleakley. Date: / /

Topic: Unit 6 Plan 6 Melting Point Depression in Solids.

Objectives: 1) Students will describe the importance to industry of the depression of melting points in solids such as metals and glasses. (Standards: 4- 4)

2) Students will describe and discuss the evolution of glass making through the ages and its influence on social evolution. (Standards: 4- 4)

3) Students will apply eutectic theory to real samples in lab to collect and analyze data. (Standards: 4-3)

Materials and Setup: Bunsen burners Porcelain crucibles Silica sand Leaded window glass Type K Chromel/Aluminel Thermocouple.

Safety: Students close to front should wear safety goggles. Warm before bringing to high temperature. Place hot crucibles on wire mats to cool.

Anticipatory set: 1. (3 min) Demonstrate that glass, which is made from silica-sand will melt with the of a . 2. (4 min)Ask students to predict whether or not the silica sand will melt with the heat of two Bunsen burners. Have students discuss their predictions in small groups as the crucible of sand is brought to temperature. 3. (2 min) Use thermocouple to demonstrate temperature of melting glass and heated sand. 4. (5 min) Have student volunteers lead discussion with class as to why the silica does not belt though the glass does.

Instruction: • (5 min) Instruct depression of melting point with addition of impurities to solids. • (10 min) Outline historical development of commercial glass from ancient times to modern. • (10 min) Give typical formulations of some types of glass and discuss commonalities between fluxing agents. • ( 5 min) Discuss field trip to corning Glass works and assign tasks to student volunteers to enhance class involvement.

Homework: 1. Use the Internet, libraries and other sources to investigate the formulations of glass in ancient times. 2. Discover the way that glass was flattened to form window- panes during the early 1800s. 3. Write a short essay (1-3 pages) discussing the above topics.

Assessment: • Essays will be collected and graded • A quiz will be given prior to the unit exam • A unit exam will include similar problems to the homework set • Class discussions.

Regents Chemistry Lab. Name: ………………………………...

Title: Melting point Depression / Glass Making

Purpose 2. To experimentally demonstrate that the melting point of silica sand is lowered by the addition of impurities. 3. To form “soda-lime” glass by fusing silica sand.

Materials 2 Aluminel crucibles digital balance Ring stand and clay triangle Mortar and pestle gas + oxygen torches or furnace Bunsen burners Goggles and dust masks

Reagents SiO2 (Silica sand – Silicon dioxide) Na2O () CaO () (lime) MgO ( 11 Oxide)

Safety • Wear your safety goggles while working with the chemicals. • All mixing, measuring, or grinding of sodium oxide must be done under the fume hood. • Don’t get the sodium oxide or any mixture containing sodium oxide on your skin. If you do so, wash it off immediately with lots of cold water. Tell the instructor. • Wear dust masks if students inhale silica dust.

Procedure Part I. Comparison of the melting points of glass and silica sand. 1. With your goggles on, use your tongs to hold a segment of in the burner flame and see if it will melt. Don’t touch it, even if it looks cold. What observations can you make about the glass?

2. Now place a small scoop of silica sand in one of your crucibles and heat it as strongly as possible. Does it melt?

Part 2. Preparation of the mixture.

2. Measure out each of the following materials In this order and add them to the mortar 72.68% of silica sand 12.76% calcium oxide 13.25% sodium oxide (remember that you will add this in the fume hood.) 0.26% magnesium oxide. NOTE: If using finely ground silica, 5.0grams is sufficient.

3. Use the mortar and pestle to grind the above mixture into a fine powder. 4. Scrape all the mixture into the crucible, place the crucible in the clay triangle on the ring stand and heat strongly with the torch until the mixture melts. Alternatively place samples in furnace at 9500C for four hours. 5. Remember to wear your goggles during heating and avoid inhaling any smoke or . 6. Make notes as you work of all changes that you observe. 7. Once the mixture has fused into “glass” use crucible tongs to place the crucible on a wire mat on the desk and cool it by fanning. DON’T TOUCH IT YET! 8. Once the crucible is cool to touch gently tap out the glass onto the bench. 9. Use a brush, to brush the “dross” off the surfaces of the glass.

Data – Part I. Describe in detail the observations that you make as the glass forms.

Calculations – Part I. 1. How many moles of each ingredient were used in this experiment?