ChemistryLab2ReportDensityDetermination：化学实验室报告2密度的测定.docx

Date:Period:Name:Experiment # 2“Density Determination”Pre Lab DiscussionChemistry is the study of matter, which is usually defined as anything that has mass and volume. You already have some experience determining mass in the laboratory. In this experiment, you will measure volumes of different materials, using direct and indirect methods. You will also use the relationship between the mass and volume of a substance to determine its density.Volumes of liquids are measured directly in a graduated cylinder. Liquid quantities dealt with in the laboratory are usually expressed in milliliters (mL), although larger volumes are expressed in liters (L). Volumes of regularly shaped geometric solids can be calculated from direct measurements of their dimensions. For example, the volume of a rectangular solid is calculated by multiplying its length, width and height (V = l x w x h). Volumes of solids are usually expressed in cubic centimeters (cm3).Many solids do not lend themselves to direct measurement of their dimensions. These include irregularly shaped objects, such as rocks, and regularly shaped objects that are too small to be measured with accuracy. Volumes of such solids are measured by water displacement. If a solid is totally immersed in a liquid, such as water, the solid will push aside or displace, a volume of water equal to its own volume. Thus, each milliliter of water displaced by a solid represents one cubic centimeter of solid volume.Density is an important property of matter. By itself, or in conjunction with other properties, density can be used to identify substances. Density is defined as the quantity of matter in a given unit of volume. This relationship, expressed mathematically, is Density =MassVolume You will be expected to use the measuring skills and techniques developed in earlier laboratory sessions and in the first part of this experiment to find the mass and volume of different substances. You will use this data to calculate the densities of these substances by algebraic and graphical means.PurposeLearn and practice techniques and calculations for determining volume and density of a substance.EquipmentLab balanceGraduated cylinders, 100mL and 10mLBeaker, 250mLMetric Ruler Regular-shaped object (block)Irregular-shaped object (pipe) TI-83+ calculatorMaterialsTap waterUnknown liquid A or BProcedurePart A Measuring Mass and Volume directly(Record your answers in Results Table A)1. Check your balance is zero-ed with nothing on the pan. Re-calibrate the balance as necessary, if you have difficulty then ask your teacher for assistance before continuing.2. Weigh the mass of a dry 250 mL beaker. Record this value in data table A.3. Using the 100 mL graduated cylinder, measure out exactly 20.0 mL of water into the dry 250 mL beaker. Weigh the combined mass on the balance and subtract the mass of the beaker. Record the mass of water added in the data table A below. 4. Repeat step 3 above, measuring the mass of the volumes specified in data table APart B Measuring Mass and Volume of an Unknown Liquid(Record your answers in Results Table B)8. Weigh the mass of a 10 mL graduated cylinder. Record this value in data table B. Circle the letter of your unknown in data table B9. Using the 50 mL beaker, measure out exactly 2.0 mL of your unknown into the 10 mL graduated cylinder. Weigh the combined mass on the balance and subtract the mass of the graduated cylinder. Record the mass of liquid added in data table B below. 10. Repeat step 9 above, measuring the mass of the volumes specified in data table B.Part C Measuring Volumes of Solids by direct and indirect methods(Record your answers in Results Tables C and D)14. Using the metric ruler, measure the dimensions of your rectangular block. Record these dimensions in data table C.15. Determine the mass of the rectangular block and record this in data table C.16. Determine the mass of the pipe section and record this in data table D.17. Fill the 100 mL graduated cylinder with approximately 50 mLs of tap water. Record the exact water level in your data table D. Fully immerse the pipe section in the graduated cylinder, record the new water level in data table D.16. Clean and dry all lab equipment, return any used unknown liquid to the front bench. You will be asked to account for the condition of all lab equipment before leaving the lab.Results Table Pay attention to significant figures! Data Table A Water Data Table B Unknown Liquid A or BMass, 250mL beaker = _ Mass, 10mL graduated cylinder = _VOLUME (ML)MASS (GRAMS)020.040.060.080.0100.0VOLUME (ML)MASS (GRAMS)02.04.06.08.010.0 Data Table C Rectangular block Data Table D Pipe sectionLENGTH (CM)WIDTH (CM)HEIGHT (CM)Volume (cm3)Mass (g)FINAL WATER LEVEL(ML)INITIAL WATER LEVEL(ML)Volume, Object (mL)Mass (g)Graphical Analysis Two graphs are required!1. Using graph paper; plot a graph of mass as a function of volume for both water and the unknown liquid. (Hint: mass is the dependent variable and volume is the independent variable). Be sure to provide a descriptive title, and labels (with units) for each axis, for each graph.2. For each graph; make the scales for each axis as large as possible, draw the line of best fit for the data set and determine the equation of this line in slope-intercept form. (Show all your work on the graph paper)Conclusions & Questions answer each of the following in the space provided1. What is the value of the slope of the graph representing water? What does this number represent?Slope = (include units)2. What is the value of the slope of the graph representing the unknown liquid? What does this number represent?Slope = (include units)3. Using the slope values, determine which liquid would float if they were combined. Explain your answer.Liquid = Explanation:4. Using the information supplied below, determine the identity of the unknown liquid. Justify your answer.Unknown liquid = Explanat