an inquiry lab. get out lab sheets and logbook
TRANSCRIPT
GOAL To determine the type of bonding in
unlabeled chemicals using physical and chemical properties of substances with ionic, molecular, and metallic bonds.
IONIC COMPOUNDS compounds containing a metal and a
nonmetal strong electrostatic attractions between positive and negative ions
formulas given in the simplest ratio of elements
crystalline structures that are solids at room temperature
ions that form a crystal lattice structure. compounds that melt at high
temperatures Substances that are good conductors of
electricity in the molten or dissolved state
COVALENT COMPOUNDSnonmetals attracted to other nonmetals formulas that are given in the true ratios
of atoms substances that may exist in any state of
matter at room temperature (solid, liquid, or gas)
compounds that melt at low temperaturessubstances that are nonconductors of
electricity
POLAR VERSUS NONPOLARPolar Covalent - NM/NM or M/NM usually dissolves in water Usually higher in mass than nonpolar
substances More likely to be solids.
Nonpolar Covalent – NM/NM Does not dissolve in water Usually not solids.
METALLIC COMPOUNDSsubstances that are metalsa “sea” of mobile or delocalized electrons
surrounding a positively charged metal centeran attraction between metal ions and
surrounding electrons formulas written as a neutral atom (Mg, Pb)solids with a crystalline structure at room
temperaturea range of melting points—usually depending
on the number of valence electronssubstances that are excellent conductors of
electricity since the electrons in the “sea” are free to move.
SAFETY AND DISPOSAL Safety goggles should be worn at all
times in the laboratory. Be cautious of acidic and basic solutions
since they can cause skin burns and eye damage.
Liquids and solids are to be disposed of in properly labeled waste containers per MSDS guidelines.
Galvanized iron square has sharp edges – handle with care to prevent cuts.
MATERIALS Universal indicator, 0.1M hydrochloric
acid (HCl), 0.1M sodium hydroxide (NaOH), 95 % Ethanol(C2H5OH); Ice, Magnifying lens, micro-scale wellplate, Hexane, Phenolphthalein, Conductivity tester (metals and aqueous only), Distilled water, pH paper, wooden splints, food can lid (iron square), cotton swabs, MSDS for all knowns and unknowns used, toothpicks, magnet, sandpaper, hot plate.
PRELAB PREPARATION You will be given four KNOWN
chemicals (1–10 grams each) in small containers.
The containers are labeled with the name, formula, and CAS number.
You have an MSDS for each compound.
PRELAB GUIDED QUESTIONS1. Review the electronegativities of the
elements. Review electronegativity values and trends using the periodic table.
2. Have a discussion with your lab partner(s) about the type of bonding represented by the chemicals in this lab: nonpolar covalent, polar covalent, ionic, and metallic.
PRELAB GUIDED QUESTIONS
**Replacing Iodine with STEARIC ACID
white solid, MP 67°C, insoluble in water, NM/NM, nonpolar covalent
PRELAB GUIDED QUESTIONS3. Compare the type of bond with regard
to the properties below using Table 1 and explain any relationships. HINT: Think of what is happening between the bonded atoms as well as what occurs between the particles.
a. melting pointb. solubility in 25oC water
4. Predict the properties of each substance below based on Table 1.
PART ONEPractice with Instrumentation and
ProcedureThe purpose of this portion of the lab is to identify properties that allow one to determine the type of bonding in a substance and to carry out tests that allow one to characterize these properties.
PROCEDURE1. Given four known compounds, choose at least
four different tests to study physical and chemical properties of each of the given substances.
2. Based on your results, you will develop a system that will help determine whether an unknown solid is ionic, covalent (polar or nonpolar), or metallic using these tests.
3. Possible tests include: color, solubility in water, conductivity of the solid, conductivity in water, pH of the solution in water, solubility in ethanol, solubility in hexanes, high/low melting point (order of melting if qualitative), reaction with 0.1M HCl, reaction with 0.1M NaOH, and magnetism.
PROCEDURE4. Select at least four tests, quantitative
and qualitative, and write a detailed procedure to carry out the tests.
5. Refer to the Materials section for guidance on available materials.
6. Create a data table to record results.7. Performs tests8. Melting point will be done qualitatively
using a can lid to compare relative melting time.
NEXT Once you finish Part One, turn in the
four film canisters – potassium chloride, sucrose, zinc, and stearic acid.
You will pick up your five unknowns. You are responsible for returning your
unknowns to me each day.
PART TWOThe InvestigationProcedure The knowledge acquired in the Practice section for known
compounds will now be applied in order to determine the type of bond for five unknown solids. Given five unknown compounds, you will choose at least four different tests to study physical and chemical properties of the substances. Based on your results, you will develop a system that will help determine whether an unknown solid is ionic, covalent (polar or nonpolar), or metallic using these tests. Possible tests include color, solubility in water, conductivity of the solid, conductivity in water, pH of the solution in water, solubility in ethanol, solubility in hexanes, high/low melting point (order of melting if qualitative), reaction with 0.1 M HCl, reaction with 0.1 M NaOH, and magnetism.
You should select at least four tests, quantitative and qualitative, and write a detailed procedure to carry out the tests. Refer to the Materials section for guidance on available materials.
DATA COLLECTION AND COMPUTATION
Create a data table to record results. After you have completed your procedure, complete data table. Identify the bond type in each unknown. Using the list of all of the unlabeled bottles (the unknowns), your results, and the MSDS for the unknowns, identify the five chemicals you tested.
CONCLUSIONArgumentation and Documentation Answer the questions that follow.
Post lab Assessment Answer the questions that follow.
WRITING THE LAB REPORT One report per group. includes title page, goal, materials you
used in both parts, prelab guiding question answers, Part One data table, Part One practice question answers, Part Two detailed procedure, Part Two data table, argumentation and documentation question answers, and post lab assessment question answers.
Each partner should initial the part that he/she wrote in the final report.
HELPFUL HINTSEverything you need is at your desk except: Cotton swabs, extra toothpicks, and
extra splints are on the back table. Chemicals on trays on back table are
NOT for this lab. Ice at lab desk #1 Unknowns at lab desk #1. Must turn in
four knowns before getting unknowns. Return unknowns to front desk each day. Unplug hot plate before leaving for the
day.
GET STARTED Wear goggles Get your unknowns from the front. If you need the four knowns from
yesterday, get them from me. Lab materials will be out through
Wednesday. Group lab report is due Friday, Dec. 6.
ADD PART ONE PROCEDURE TO LAB REPORT. NOT LISTED BUT SHOULD BE INCLUDED.
POTENTIAL COMPOUNDSIONIC Ammonium chloride Magnesium oxide Sodium carbonate Sodium hydrogen carbonate Sodium chloride Copper(II) sulfate, anhydrous Potassium nitrate Calcium carbonate Sodium acetateMETALLIC aluminum Iron Copper magnesium
POLAR COVALENT Citric Acid Salicylic acid Sucrose Urea dextrose methylcellulose
NONPOLAR COVALENT wax/paraffin silicon dioxide Agar Lauric acid