General chemistry 2 lab manual answers

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CHE 1401 School of Science & Engineering School of Science & Engineering L LA AB BO OR RA AT TO OR RY Y M MA AN NU UA AL L F FO OR R GENERAL CHEMISTRY I GENERAL CHEMISTRY I Last Update: 7 July 2015 Last update: July 2015 1 CHE 1401 To the Student You are about to engage in what for most of you will be a unique experience. You are going to collect experimental data on your own and use your reasoning powers to draw logical conclusions about the meaning of these data. Your laboratory periods are short, and in most instances, there will not be enough time to come to the laboratory unaware of what you are to do, collect your experimental data, make conclusions and/or calculations regarding them, clean up, and hand in your results. Thus, you should read the experimental procedure in advance so that you can work in the lab most efficiently. After you’ve read through the experiment, try to answer the review questions we’ve included at the end of each experiment. These questions will help you to understand the experiment in advance. Some of your experiments will also contain an element of danger. For this and other reasons, your lab instructor is present to assist you. He is your friend. Treat him well and above all don’t be afraid to ask him questions. Within reason, he will be glad to help you. Chemistry is an experimental science. The knowledge that has been accumulated through previous experiments provides the basis for today’s chemistry courses. The information now being gathered will form the basis of future courses. There are basically two types of experiments that chemists conduct: 1 Qualitative – to determine the nature of processes, which are often unanticipated and sometimes unpredictable. 2 Quantitative- to determine the amount of a measurable change in mass, volume, or temperature, for example, including the time rate of change on processes for which the qualitative data are already known. It is much easier to appreciate and comprehend the science of Chemistry, if you actually participate in experimentation. Although there are many descriptions of the scientific method, the reasoning process involved is difficult to appreciate without performing experiments. Invariably there are experimental difficulties encountered in the laboratory that require care and patience to overcome. There are four objectives for you, the student, in the laboratory: 1 To develop the skills necessary to obtain and evaluate a reliable original result. 2 To record your results for future use. 3 To be able to draw conclusions regarding your results (with the aid of some coaching and reading in the beginning). 4 To learn to communicate your results critically and knowledgeably. By attentively reading over the experiments in advance, and by carefully following directions and working safely in the laboratory, you will be able to accomplish all these objectives. Best wishes for an error-free and accident-free term Lab Manual iii CHE 1401 SAFETY IN THE LABORATORY Safety in the laboratory must be emphasized. The compounds you will work with do have some hazards associated with them. Therefore, it is important to follow the safety rules outlined in this lab manual. You should assume that all compounds encountered in the laboratory are toxic and handle them accordingly. Safety goggles for eye protection are recommended and lab coats are to be worn by all students at all times when entering the laboratory. Many chemicals, common in chemical laboratories, will make holes in clothing. Always wash your hands thoroughly when leaving the laboratory. The location and use of the safety equipment in laboratory were already discussed in CHE1401 and will be reminded by your instructor the first day the laboratory class meets. You should become familiar with the proper use of the safety shower, eye-wash fountain, fire blanket and fire extinguisher. Report any accidents which occur immediately to the laboratory supervisor. Safety rules to be strictly followed by all students: 1. Wear goggles when required. 2. Do not touch chemicals with your hands. Spatulas will be provided for handling solid materials. 3. Do not eat or drink in the laboratory. 4. Do not taste any chemical. 5. Do not smell any chemicals directly. Use your fingers to waft the odor to your nose. 6. Do not pipet solutions by mouth. Rubber pipet bulbs are provided at each lab station. 7. Do not put flammable liquids near an open flame. 8. When heating a test tube, make certain that the open end of the tube is directed away from the students. 9. When finished with your Bunsen Burner for a given portion of an experiment, turn it off. 10. Do not sit on the lab benches. 11. Do not engage in games in the laboratory. Failure to follow this rule will result in immediate dismissal from the lab and subsequent conduct action. 12. Do not pour any chemicals into a sink without authorization from the instructor. 13. Notify your instructor if a mercury spill should occur. 14. All broken glassware should be cleaned up immediately. The instructor should be notified of all breakage, especially if a thermometer is involved. 15. Do all reactions involving malodorous, noxious or dangerous chemicals in a fume hood. 16. If a chemical gets on your skin, immediately wash the affected area with large quantities of water. The instructor should be notified; no matter how insignificant the incident might seem. 17. When pouring one liquid into another, do so slowly and cautiously. To dilute an acid, pour the acid into the water; never pour water into an acid. 18. No student shall be permitted to work alone in the lab, you should be supervised by a laboratory instructor (or the lab technician during make up sessions). 19. Exercise good housekeeping practices in the laboratory. Be sure that the lab benches remain free of disorder during the experiment. In the event of a spill, clean the area immediately and be sure to use a wet sponge to wipe off the work station at the end of the lab session. 20. Know what you have to do before entering the lab. Read the experiment carefully before coming to the laboratory. For more information, a booklet titled “Student’s Chemistry Laboratory Safety Manual” will be provided to you in your first lab session. Please get acquainted with it. Be cautious and think about what you are doing Lab Manual iv CHE 1401 Safety rules The laboratory can be but is not necessarily a dangerous place. When intelligent precautions and a proper understanding of techniques are employed, the laboratory is no more dangerous than any other classroom. Most of the precautions are just common-sense practices. These include the following: 1. Wear approved eye protection when required while in the laboratory. Your safety eye protection may be slightly different from that shown, but it must include shatterproof lenses and side shields to provide protection from splashes. Typical eyewash Approved eye protections The laboratory has an eyewash fountain available for your use. In the event that a chemical splashes near your eyes, you should use the fountain BEFORE THE MATERIAL RUNS BEHIND YOUR EYEGLASSES AND INTO YOUR EYES. The eyewash has a "panic bar," which enables its easy activation in an emergency. 2. Eating, drinking, and smoking are strictly prohibited in the laboratory at all times 3. Know where to find and how to use safety and first-aid equipment. 4. Consider all chemicals to be hazardous unless you are instructed otherwise. Dispose of chemicals as instructed by your instructor. Follow the explicit instructions given in the experiments. 5 If chemicals come into contact with your skin or eyes, wash immediately with copious amounts of water and then consult your laboratory instructor. 6. Wear shoes at all times. “Baboosh” shoes are not allowed in the laboratory. Lab Manual v CHE 1401 6 Never taste anything. Never directly smell the source of any vapor or gas; instead, by means of your cupped hand, bring a small sample to your nose (see figure below). Chemicals are not to be used to obtain a "high" or clear your sinuses. Wafting vapors towards one’s nose 8. Perform in the hood any reactions involving skin-irritating or dangerous chemicals and/or ill-smelling chemicals. A typical fume exhaust hood is shown below. Fume hood found in the laboratory Exhaust hoods have fans to exhaust fumes out of the hood and away from the user. The hood should be used when noxious, hazardous, and flammable materials are being studied. It also has a shatterproof glass window, which may be used as a shield to protect you from minor explosions. Reagents that evolve toxic fumes are stored in the hood. Return these reagents to the hood after their use. Lab Manual vi CHE 1401 9. Never point a test tube that you are heating at yourself or your neighbour. It may erupt like a geyser. Beware of spattering 10. Do not perform any unauthorised experiments. 11. Clean up all broken glassware immediately. 12. Always pour acids into water, not water into acid, because the heat of solution will cause the water to boil and the acid to spatter. 13. Avoid rubbing your eyes unless you know that your hands are clean. 14. NOTIFY THE INSTRUCTOR IMMEDIATELY IN CASE OF AN ACCIDENT 15 Many common reagents, for example, alcohols, acetone, and especially ether, are highly flammable. Do not use them anywhere near open flames. 16. Observe all special precautions mentioned in experiments. 17. Learn the location of fire protection devices. In the unlikely event that a large chemical fire occurs, a powder extinguisher and a CO 2 extinguisher are available in the lab. In order to activate the extinguisher, you must pull the metal safety ring from the handle and then depress the handle. Direct the output of the extinguisher at the base of the flames. The carbon dioxide smothers Powder and CO extinguishers 2 the flames and cools the flammable material quickly. If you use the fire extinguisher, be sure to return the extinguisher in at the stockroom so that it can be refilled immediately. If the carbon dioxide extinguisher does not extinguish the fire, evacuate the laboratory immediately and call the security. One of the most frightening and potentially most serious accidents is the ignition of one’s clothing. Therefore, certain types of clothing are hazardous in the laboratory and must not be worn. Since sleeves are most likely to come closest to flames, ANY CLOTHING THAT HAS BULKY OR LOOSE SLEEVES SHOULD NOT BE WORN IN THE LABORATORY. Ideally, students should wear laboratory coats with tightly fitting sleeves. Long hair also presents a hazard and must be tied back. If a student's clothing or hair catches fire Lab Manual vii CHE 1401 his or her neighbours should take prompt action to prevent severe burns. Most laboratories have a water shower for such emergencies. A typical laboratory emergency water shower has the following appearance. In case someone's clothing or hair is on fire, immediately lead the person to the shower and pull the metal ring. Safety showers generally dump 151 to 190 litres of water, which should extinguish the flames. These showers cannot be shut off once the metal ring has been pulled. Therefore, the shower cannot be demonstrated. (Showers are checked for proper operation on a regular basis, however.) 18. Whenever possible use hot plates instead of Bunsen burners. A safety shower Lab Manual viii CHE 1401 COMMON LABORATORY EQUIPMENT Lab Manual ix CHE 1401 Lab Manual xi CHE 1401 EXPERIMENT 1 Basic laboratory techniques OBJECTIVE To learn the use of common, simple laboratory equipment. Relates to chapter 1 of “Chemistry the Central Science, 12th Ed.”. APPARATUS AND CHEMICALS Balance Iron ring and ring stand 150-mL beaker Bunsen burner and hose 50- or 100-mL graduated cylinder Clamp 10-mL pipet Rubber bulb 25-mL Erlenmeyer flask Thermometer 125-mL Erlenmeyer flask INTRODUCTION Chemistry is an experimental science. It depends upon careful observation and the use of good laboratory techniques. In this experiment you will become familiar with some basic operations that will help you throughout this course. Your success as well as your safety in future experiments will depend upon your mastering these fundamental operations. Because every measurement made in the laboratory is really an approximation, it is important that the numbers you record reflect the accuracy of the device you use to make the measurement. Our system of weights and measures, the metric system, was originally based mainly upon fundamental properties of one of the world's most abundant substances, water. The system is summarized in Table 1.1. Conversions within the metric system are quite simple once you have committed to memory the meaning of the pre-fixes given in Table 1.2. Recently, scientists have started to use a briefer version of the metric system of units in which the basic units for length, mass, and time are the meter, the kilogram, and the second. This system of units, known as the International System of Units, is commonly referred to as the SI system and is preferred in scientific work. A comparison of some common SI, metric, and English units is presented in Table 1.3. Conversions within the metric system are quite easy if you remember the definitions for the prefixes and use dimensional analysis in problem solving. Lab Manual 1 CHE 1401 Table 1.1 Units of Measurement in the Metric System Measurement Unit and definition 3 Mass or weight Gram (g) = weight of 1 cubic centimeter (cm ) of water at 4°C and 760 mm Hg Mass = quantity of material Weight = mass x gravitational force Length Meter (m) =100 cm =1000 millimeters (mm) =39.37 in. Volume Liter (L) =volume of 1 kilogram (kg) of H O at 4° C 2 Temperature °C, measures heat intensity: 5 9  o o o o C F 32 or F C 32  9 5  Heat 1 calorie (cal), amount of heat required to raise 1 g of water 1°C 1 cal = 4.184 joules (J) Density d, usually g/ml, for liquids and g/L for gases: d = mass/unit volume Specific gravity Sp gr, dimensionless Sp gr = density of a substance/density of a reference substance The quantities presented in Table1.1 are measured with the aid of various pieces of apparatus. A brief description of some measuring devices follows. Table 1.2 The Meaning of prefixes in the metric system Prefix Meaning Abbreviation (power of 10) -15 femto- 10 f -12 pico- 10 p -9 nano- 10 n -6 micro- 10 µ -3 milli- 10 m -2 centi- 10 c -1 deci- 10 d 3 kilo- 10 k 6 mega- 10 M 9 giga- 10 G Table 1.3 Comparison of SI, Metric, and English Units Physical quantity SI unit Some common Metric units Conversion factors 2 Length Meter (m) Meter (m) 1 m = 10 cm Centimeter (cm) 1 m = 39,37 in. 1 in. = 2.54 cm 3 3 Volume Cubic Liter (L) 1 L = 10 cm 3 -3 3 Meter (m ) Milliliter (mL) 1L = 10 m 1L = 1.06 qt 3 Mass Kilogram (Kg) Gram (g) 1 kg = 10 g Milligram (mg) 1 kg = 2.205 lb 1 lb = 453.6 g Energy Joule (J) Calorie (cal) 1 cal = 4.184 J Temperature Kelvin (k) Degree Celsius (°C) 0 K =- 273.15 °C 5 o o C F 32 9 3 A mL is the same volume as a cubic centimeter: 1 mL = 1 cm Lab Manual 2 CHE 1401 Laboratory Balance A laboratory balance is used to obtain the mass of various objects. There are several different varieties of balances, with various limits on their accuracy. Two of these balances are pictured in Figure 1.1. Most modern laboratories possess single-pan balances. These are the most accurate balances; generally, they are also the simplest to use and are the most delicate and expensive. The amount of material to be weighed and the accuracy required determine which balance you should use. Figure 1.1 Digital electronic balances. The balance gives the mass directly when an object to be weighed is placed on the pan. Graduated Cylinders Graduated cylinders are tall, cylindrical vessels with graduations scribed along the side of the cylinder. Since volumes are measured in these cylinders by measuring the height of a column of liquid, it is critical that the cylinder has a uniform diameter along its entire height. Obviously, a tall cylinder with a small diameter will be more accurate than a short one with a large diameter. A liter (L) is divided into milliliters (mL) such that 1 mL = 0.001 L and 1 L = 1000 mL. Graduated cylinder Thermometers Most thermometers are based upon the principle that liquids expand when heated. Most common thermometers use mercury as the liquid. These thermometers are constructed so that a uniform-diameter capillary tube surmounts a mercury reservoir. To calibrate a thermometer, one defines two reference points, normally the freezing point of water (0°C, 32°F) and the boiling point of water (100°C, 212°F) at 1 atm of pressure (1 atm = 760 mm Hg). Once these points are marked on the capillary, its length is then sub-divided into uniform divisions called degrees. There are 100° between these two points on the Celsius, (°C, or centigrade) scale and 180° between those two points on the Fahrenheit (°F) scale. Lab Manual 3 CHE 1401 Pipets Pipets are glass vessels that are constructed and calibrated so as to deliver a precisely known volume of liquid at a given temperature. The markings on the pipet illustrated in Figure 1.2 signify that this pipet was calibrated To Deliver (TD) 10.00 mL of liquid at 25°C. Always use a rubber bulb to fill a pipet. NEVER USE YOUR MOUTH A TD pipet should not be blown empty. It is important that you be aware that every measuring device, regardless of what it may be, has limitations in its accuracy. Moreover, to take full advantage of a given measuring instrument you should be familiar with or evaluate its accuracy. Careful examination of the subdivisions on the device will indicate the maximum accuracy you can expect of that particular tool. Figure1.2 A typical volumetric pipet, rubber bulbs, and the pipet filling technique. In this experiment you will determine the accuracy of your 10-mL pipet. The approximate accuracy of some of the equipment you will use in this course is given in Table 1.4. Not only should you obtain a measurement to the highest degree of accuracy that the device or instrument permits, but you should also record the reading or measurement in a manner that reflects the accuracy of the instrument. For example, a mass obtained from an analytical balance should be observed and recorded to the nearest 0.01 g. This is illustrated in Table 1.5. Lab Manual 4 CHE 1401 Table1.4 Equipment Accuracy Equipment Accuracy Analytical balance ±0.0001 g (±0.1 mg) Top-loading balance ±0.001 g (1 mg) Graduated cylinder ±0.1 mL Pipet ±0.02 mL Buret ±0.02 mL Thermometer ±0.2°C Table 1.5 Obtaining Significant Figures Analytical balance Top loader 85.9 g (incorrect) 85.9 g (incorrect) 85.93 g (incorrect) 85.93 g (incorrect) 85.932 g (incorrect) 85.932 g (correct) 85.9322 g (correct) PROCEDURE A. The Bunsen Burner Melting points of metals The Bunsen burner is a convenient source of heat in the laboratory. Although there are several varieties, their principle of operation is the same and is similar to that of the common gas stove. The Bunsen burner requires gas and air, which it mixes in various proportions. The amount of air and gas mixed in the chamber is varied by use of the collar illustrated in Figure 1.3. The relative proportions of gas and air determine the temperature of the flame. Examine your burner and locate the gas and airflow adjustments (valves) (see Figure 1.3). Determine how each valve operates before connecting the burner to the gas outlet. Close both valves; connect a rubber hose to the gas outlet on the burner and the desk; then open the desk valve about two-thirds of the way. Figure1.3 Typical Busen burner. Strike a match or use a gas lighter. Hold the lighted match to the side and just below the top of the barrel of the burner while gradually opening the gas valve on the burner to obtain a flame about 7 or 10 cm high. Gradually open and adjust the air valve until you obtain a pale blue flame with an inner cone as shown in Figure 1.3. Flame temperatures can be observed using the melting points of metals. Lab Manual 5 CHE 1401 Adjust the burner to a non-luminous flame to measure the temperatures in the various regions of the flame. Use crucible tongs to hold 2-cm strips of iron wire, copper wire, and aluminum wire in the various regions of the flame. The melting point of iron is 1535 °C, that of copper is 1083 °C, and that of aluminum is 660 °C. On the Report Sheet, record the estimated temperature of the flame in the regions designated in Figure 1.4.  Top of the outer cone  Center of the outer cone  Top of the inner cone Metal Melting point  Center of the inner cone o ( C) Iron (Fe) 1535 Copper (Cu) 1083 Aluminium (Al) 660 Figure 1.4 Regions of the flame for temperature measurement. B. The Graduated Cylinder Examine the 100-mL graduated cylinder and notice that it is scribed in milliliters. Fill the cylinder approximately half full with water. Notice that the water meniscus (curved surface of the water) is concave (see Figure 1.5). When water is the liquid, the lowest point on the curve is always read as the volume, never the upper level. Avoid errors due to parallax; different and erroneous readings are obtained if the eye is not perpendicular to the scale. Read the volume of water to the nearest 0.1 mL. Record this volume. Measure the maximum amount of water that your 125-mL Erlenmeyer flask will hold. Record this volume. + proper position + Figure 1.5 Proper eye position for taking volume readings. The meniscus reading here is 50.0 mL. Lab Manual 6 CHE 1401 C. Using the balance to calibrate your 10-mL pipet Weighing an object on a single-pan balance is a simple matter. Because of the sensitivity and the expense of the balance (some cost more than 2500) you must be careful in its use. Directions for operation of single-pan balance vary with make and model. Your laboratory instructor will explain how to use the balance. Regardless of the balance you use, proper care of the balance requires that you observe the following: 1. Do not drop an object on the pan. 2. Center the object on the pan. 3. Do not place chemicals directly on the pan; use a beaker, watch glass, weighing bottle, or weighing paper. 4. Do not weigh hot or warm objects; objects must be at room temperature. 5. Return all weights to the zero position after weighing. 6. Clean up any chemical spills in the balance area. 7. Inform your instructor if the balance is not operating correctly; do not attempt to repair it yourself. The following method is used to calibrate a pipet or other volumetric glassware. Obtain about 40 mL of distilled water in a 150-mL beaker. Allow the water to sit on the desk while you weigh and record the weight of an empty, dry 25-mL Erlenmeyer flask (tare) to the nearest 0.1 mg. Measure and record the temperature of the water. Using your pipet, pipet exactly 10.00 mL of water into this flask and weigh the flask with the water in it (gross) to the nearest 0.1 mg. Obtain the weight of the water by subtraction (gross – tare= net). Using the equation below and the data given in Table 1.6, obtain the volume of water delivered and therefore the volume of your pipet. mass m density volume V Normally, density is given in units of grams per milliliter (g/mL) for liquids, grams 3 per cubic centimeter (g/cm ) for solids, and grams per liter (g/L) for gases. Repeat this procedure in triplicate-that is, deliver and weigh exactly 10.00 mL of water three separate times. Lab Manual 7 CHE 1401 The calculation is: 10.0025 g V 10.0249 mL 10.02 mL 0.997770 g / mL The volume must be rounded off to 10.02, because the pipet's precision can be determined only to within ±0.02 mL. The precision of a measurement is a statement about the internal agreement among repeated results; it is a measure of the reproducibility of a given set of results. The arithmetic mean (average) of the results is usually taken as the "best" value. The simplest measure of precision is the average deviation from the mean. The average deviation is calculated by first determining the mean of the measurements, then calculating the deviation of each individual measurement from the mean and, finally, averaging the deviations (treating each as a positive quantity). Study Example 1.2 and then, using your own experimental results, calculate the mean volume delivered by your 10-mL pipet. Also calculate for your three trials the individual deviations from the mean and then state your pipet's volume with its average deviation. EXAMPLE 1.2 The following values were obtained for the calibration of a 10-mL pipet: 10.10, 9.98, and 10.00 mL. Calculate the mean value and the average deviation from the mean. SOLUTION: 10.10 9.9810.00 mean 10.03 3 Deviations from the mean: value – mean 10.10 -10.03 = 0.07 9.98 - 10.03 = 005 10.00 - 10.03 = 0.03 0.07 0.05 0.03 Average deviation from the mean  0.05 3 The reported value is therefore 10.03 0.05 mL. Lab Manual 9 CHE 1401 REVIEW QUESTIONS You should be able to answer the following questions before beginning this experiment: 1. What are the basic units of length, mass, volume, and temperature in the SI system? 3 2. A liquid has a volume of 1.35 liters. What is its volume in mL? in cm ? 3. If an object weighs 1.47 g, what is its weight in mg? 4. Why should you never weigh a hot object? 5. What is precision? 6. Define density? Can it be determined from a single measurement? 7. What is the density of an object with a mass of 9.03 g and a volume of 0.1987 mL? 8. Weighing an object three times gave the following results: 10.2 g, 10.1 g, and 10.3g. Find the mean weight and the average deviation from the mean. 9. Normal body temperature is 98.6°F. What is the corresponding Celsius temperature? 11. What is the weight in kilograms of 950 mL of a substance that has a density of 1.274 g/mL? 12. An object weighs exactly five grams on an analytical balance that has an accuracy of 0.1 mg. To how many significant figures should this weight be recorded? 13. What is the dominant color of a properly adjusted flame from a Bunsen burner? 14. How many distinct cones does a properly adjusted non-luminous flame have on a Bunsen burner (one, two or three)? Lab Manual 10 CHE 1401 Experiment 1 Basic laboratory techniques Name(s) Date Laboratory Instructor REPORT SHEET A. Bunsen Burner Indicate the approximate temperature of the following regions of the flame (see Figure 1.4) a. region : Top of the outer cone __________ °C b. region : Center of the outer cone __________ °C c. region : Top of the inner cone __________ °C d. region : Center of the inner cone __________ °C B. The graduated cylinder Volume of water in graduated cylinder ___________________________ mL Volume of water contained in 125-mL Erlenmeyer flask _____________ mL C. Using the balance to calibrate your 10-mL pipet o 3 Temperature of water ___________ C Density of water ___________ g/cm Trial 1 Trial 2 Trial 3 Weight of Erlenmeyer (tare wt) ______ ______ ______ g Weight of Erlenmeyer plus 10 mL H 0 (gross wt) ______ ______ ______ g 2 Weight of 10 mL of H O (net wt) ______ ______ ______ g 2 Volume delivered by 10-mL pipet ______ ______ ______ mL  show calculations overleaf Mean volume delivered by 10-mL pipet __________ mL  show calculations overleaf Trial 1 Trial 2 Trial 3 Individual deviations from the mean ______ ______ ______ Average deviation from the mean ____________________ mL  show calculations overleaf Volume delivered by your 10-mL pipet ____________ mL ± __________mL Lab Manual 11 CHE 1401 EXPERIMENT 2 Identification of substances: Physical properties OBJECTIVE To become acquainted with procedures used in evaluating physical properties and the use of these properties in identifying substances. Relates to chapter 1 of “Chemistry the Central Science, 12th Ed.”. APPARATUS AND CHEMICALS Balance Capillary tubes (5) 250 mL beaker Spatula 25 mL Erlenmeyer flask Ring stand and ring 10 mL graduated cylinder Utility clamp 10 mL pipet Thermometer clamp 5 mL pipet Thermometer 50 mL beakers (2) Stirring rod Burner and hose Apparatus for boiling point determination Wire gauze Naphthalene (1 g) Small rubber bands Ethyl alcohol (15 mL) Boiling chips Cyclohexane (20 mL) Large test tubes (2) 2 unknowns (liquid and solid) Small test tubes (6) Soap solution Test-tube rack DISCUSSION PROPERTIES are those characteristics of a substance that enable us to identify it and to distinguish it from other substances. Direct identification of some substances can readily be made by simply examining them. For example, we see color, size, shape, and texture, and we can smell odors and discern a variety of tastes. Thus, copper can be distinguished from other metals on the basis of its color. PHYSICAL PROPERTIES are those properties that can be observed without altering the composition of the substance. Whereas it is difficult to assign definitive values to such properties as taste, color, and odor, other physical properties, such as melting point, boiling point, solubility, density, viscosity, and refractive index, can be expressed quantitatively. For example, the melting point of copper is 1087 °C, and its 3 density is 8.96 g/cm . As you probably realize, a specific combination of properties is unique to a given substance, thus making it possible to identify most substances just by careful determination of several properties. This is so important that large books have been compiled listing characteristic properties of many known substances. Two of the most complete references of this type that are readily available today are The CRC Handbook of Chemistry and Physics and Lange’s Handbook of Chemistry. In this experiment you will use the following properties to identify a substance whose identity is unknown to you: solubility, density, and boiling point. Lab Manual 12

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