STUDENTS 2 SCIENCE Virtual Lab Experiment Precipitates An investigation of solubility and precipitation. A classroom Experiment in Kit Form for Grades 9-12 Brief Background: Students will learn the difference between reaction precipitates like the precipitation of Basic copper carBonate from the reaction of copper chloride and sodium carBonate and those that result solely from a change in solution soluBility (water vs. isopropanol). They will learn aBout precipitation in water treatment and purification and aBout the scientists who work to provide or maintain clean water for us. Additionally, students will learn that precipitates can sometimes Be redissolved By adding another chemical compound and thus carrying out an additional chemical reaction. Safety Students and teachers must wear properly fitting goggles as they prepare for, conduct, and clean up from the activities in the kit. Read and follow all safety warnings. Also review the Materials Safety Data Sheets. Students must wash their hands with soap and water after the activities. The activities described in this kit are intended for students under the direct supervision of teachers. Student kit packaged as 13 individual units for a class size of 26. Each student package is shared by 2 students. Items in each 2-student Ziploc bag: • (1) vial labeled “CuSO4” approximately 1/4 filled with cupric sulfate • (1) empty vial laBeled “CuSO4 Solution” • (1) 4-mL vial laBeled “CaCl2” containing small amount calcium chloride • (1) vial labeled “NaHCO3” (in red lettering) approximately 1/3 filled with sodium bicarbonate © 2015 Students 2 Science Inc. All Rights Reserved. • (1) vial labeled “Na2CO3” approximately 1/3 filled with sodium carbonate • (1) empty vial laBeled “Na2CO3 Solution” • (1) empty 4-mL vial laBeled “NaHCO3 Solution” • (1) empty large vial • (1) 4-mL vial laBeled “IPA” containing 2 mL isopropanol • (1) dropper Bottle laBeled “HCl” containing 0.05N HCl • (1) mini-tuBe holder with 6 minituBes placed in the holes • (4) pipets • (2) 9oz cups (water, waste) • (1) 4 oz cup • (1) measuring cup • (4) small scoops • (1) small spoon • flat toothpicks (4 – 6) • (1) folded filter paper circle Three worksheets per group of students: • “PPT Experiment Layout.docx” sheet • “Precipitates Worksheet.docx” sheet • Precipitates Template sheet Teacher Supplied Items: Water Pre-lab Set up: Provide each 2-student team with the day’s experiment contained in the Ziploc Bag (items in the bag are listed above) and 3 handouts (listed aBove). The items in the bag should be placed on the layout sheet as described below. Remove the 9oz cup labeled “water” from each Bag and half-fill with water. Paper towels should Be available for cleanup of spills. Each student must have a pen or pencil. All students and instructors should have safety glasses and gloves. © 2015 Students 2 Science Inc. All Rights Reserved. Instructor/Teacher Procedure and guide 1. What is a precipitate? a. A precipitate is an insoluBle solid that emerges from a liquid solution. b. Precipitation may occur if the concentration of the solid exceeds its soluBility. c. It can also occur if two soluBle salts react to form a third compound that is insoluble. A" "is"an"insoluble"solid"that" emerges"from"a"liquid"solu4on! Two!types!of!precipitates:! • Precipita4on"may"occur"if"the"concentra4on"of"a" compound"exceeds"its"solubility"" !when"changing"solu4on"temperature" !when"mixing"solvents" • Reac4on"precipitate"–"forms"when"two"soluble"salts" react"in"solu4on"to"form"a"compound"that"is"insoluble"" 2. Chemical change vs. solvent/soluBility change a. Confirm worksheets and layout sheets are set up properly b. Tell students to keep pipets and scoops with their respective solutions/chemicals and not to mix them up. c. Add 2 nearly full scoops of solid sodium BicarBonate to the bicarbonate solution vial. d. Practice using the pipet to be able to add water dropwise. e. Add 2 mL of water using the pipet to the BicarBonate solution vial. f. Cap and shake vigorously to dissolve the bicarbonate. i. A small amount will not dissolve ii. The soluBility of BicarBonate in water is 100mg/mL and the two scoops contain greater than 200 mg. g. Using a clean pipet, remove a few drops of clear liquid above the remaining solid and add this to the vial containing isopropyl alcohol (IPA) h. What happened? (should oBserve BicarBonate coming out of solution) © 2015 Students 2 Science Inc. All Rights Reserved. Solubility)of)Salts) Sodium'Bicarbonate'('NaHCO3')' 100)mg)/)mL)in)water)) <)0.1)mg)/)mL)in)isopropanol)()IPA))) Calcium'Chloride'('CaCl2')' 80)mg)/)mL)in)water) ) ) i. Enter results on worksheet under “test solution sodium BicarBonate IPA”. j. Add 2 mL of water to the vial laBeled CaCl2, calcium chloride k. Cap and shake to dissolve. (solution should be clear, no precipitate) l. Add 1 mL of additional water if it is not fully dissolved. m. Add a few drops of the clear supernatant solution in the Bicarbonate vial to the vial containing the CaCl2 solution. n. OBserve (precipitate should form) i. The equation shown below gives the specifics of the reaction Between sodium BicarBonate and calcium chloride. These two compounds spontaneously react in water to form 4 different products, insoluBle calcium carBonate, soluBle sodium chloride, water, and carbon dioxide gas. ii. Calcium carBonate is the compound used By ocean coral and marine plankton to Build skeletons and for shellfish to Build the shells they need for protection. © 2015 Students 2 Science Inc. All Rights Reserved. Precipita)on,Reac)on:,, Forming,Insoluble,Calcium,Carbonate, Calcium,carbonate,solubility,,,,<,0.1,mg,/,mL,in,water, o. Record results on worksheet under “ test solution sodium BicarBonate calcium chloride”. 3. Applications to real world issues: a. Purposeful precipitation is used to remove impurities from our drinking water. b. These can be separated by filtration. i. Rayfield Jackson is a water treatment chemist for the city of Chicago. As a water treatment chemist, Rayfield is just one of many types of scientists who work to provide or maintain clean water for all of us on the earth. ii. Environmental Chemists work to limit human-caused damage to the environment. Hydrologists who study the movement, distribution, and quality of water on Earth and Wastewater Engineers who design systems that safely treat wastewater to remove harmful suBstances and return clean water back to the environment. © 2015 Students 2 Science Inc. All Rights Reserved. Scien&sts)who)help)provide)us)with) clean)water:) ! • Environmental)Chemists–)work)to)limit)human:caused) damage)to)the)environment)) • Hydrologists)–)study)the)movement,)distribu&on,)and)quality) of)water)on)Earth) • Wastewater)Engineers)):)design)systems)that)safely)treat) wastewater)to)remove)harmful)substances)and)return)it)to) the)environment) Alum is a class of compounds containing aluminum and sulfate. The 2 most common types of alum used are potassium alum and ammonium alum, and this slide shows you their chemical formula. Alum acts in two different ways to purify water. It causes suspended particles to clump together so they can Be easily filtered out. It can also precipitate certain dissolved chemicals, like phosphates. Phosphates are potentially dangerous phosphorous salts that contaminate streams and lakes from the overuse of fertilizers. The removal of phosphate By alum is an example of a reaction precipitate. © 2015 Students 2 Science Inc. All Rights Reserved. Alum%for%Water%Purifica1on% • A%class%of%chemicals%containing%aluminum% and%sulfate% – Potassium%alum%–%KAl(SO4)2% – Ammonium%alum%–%(NH4)Al(SO4)2% • When%dissolved%in%water%% – causes%suspended%par1cles%to%clump%together% – precipitates%dissolved%phosphate%% 4. Generating a precipitate: Copper salts-Copper carbonate. Solution Preparation a. Examples of Copper Salts: when copper is exposed to the effects of weather, it develops a blue-green patina. The patina is a mixture of copper salts, including oxides, carbonates, and sulfides. Students are going to make what’s called Basic copper carBonate from a solution of copper sulfate. Statue&of&Liberty& © 2015 Students 2 Science Inc. All Rights Reserved. Copper&Pa)na& New&copper&gu0er& Weathered&copper&gu0er& b. Using a clean scoop, place 4 full scoops of copper sulfate into the empty copper sulfate solution vial. c. Using the measuring cup, measure 10 milliliters of water and add it to the copper sulfate. d. Cap and shake to dissolve. Solution might remain slightly cloudy. This will not affect the experiment. Allow the vial to sit undisturBed for a few minutes to allow the undissolved particles to settle. e. Using a clean scoop, place 2 scoops of sodium carBonate into the empty sodium carBonate solution vial. f. Using the measuring cup, measure 5 milliliters of water and add it to the sodium carBonate. g. Cap and shake to dissolve. 5. Experiments in minituBes-1 a. Bottom 3 tubes (4, 5, and 6) will get 6 drops each of copper sulfate solution using a clean pipet. b. Add 1 drop of water into the first tube on the left (4). What happens? (nothing-this will be the control well) c. Add 1 drop of sodium carBonate solution to the tube second from the left (5). DO NOT MIX. Observe. (see light precipitate) d. Add 6 drops the sodium carBonate solution to the third tube (6) and mix it gently with the toothpick for just a few seconds. (heavy precipitate and bubbles=CO2) i. When copper sulfate reacts with sodium carBonate, it forms the precipitate basic copper carbonate. ii. This is one of the main compounds present in the Blue-green patina seen on the Statue of Liberty and weathered copper roofs and gutters. e. Enter results and observations on worksheet. © 2015 Students 2 Science Inc. All Rights Reserved. Reac%on(of(Copper(Sulfate(and( Sodium(Carbonate( 2(CuSO4((aq)((+((2(Na2CO3((aq)((+((H2O((((→( (Cu2(OH)2CO3((s)((+((2(Na2SO4((aq)((+((CO2((g)!! The!precipitate!is!“basic!copper!carbonate”:! Cu2(OH)2CO3( ! The!gas!is!“carbon!dioxide”:! !CO2(! When copper sulfate reacts with sodium carBonate, it forms the precipitate Basic copper carBonate.