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1 Experiment 3: Measurements, the Metric System & Density Objective The purpse f experiment is t becme familiar with the metric system by taking measurements using metric. Additinally, the purpse f this experiment is t take measurements using varius measuring devices and then reprt these measurements with the crrect precisin based n the apparatus used. Each measurement will be cnverted t ther using dimensinal analysis with the answers reprted t the crrect number f significant figures. Materials Alchl Thermmeter Metric Ruler Metallic Cube Unknwn Brand new #2 Pencil Lab Manual 100 and 250 ml beakers Empty 2-L sda bttle with cap 10 ml, 25 ml, 100 ml prefilled with clred liquid 500 ml graduated cylinder Intrductin Additinal Reading: Ch , Chemistry in ur Lives, 5 th Editin Timberlake. Chemistry and Measurements. Fr this experiment, yu will be taking measurements with several different labratry tls. Emphasis in grading will be placed n recrding measurements with prper significant figures and with prper. 23

2 Prcedure Part I Metric Measurements & Estimates Measuring Temperature Temperature is measured in Celsius r Kelvin in a labratry setting. The lines n the thermmeter represent 0.1 C increments in temperature. Yur recrded measurement f the temperature shuld estimate between the lines and carry with it tw decimal places r precisin t 0.01 C. Fill a 250 ml beaker 1/2 full (125 ml) with tap water and allw it t reach rm temperature, abut 30 minutes. Prceed with ther parts f the labratry while yu wait fr the temperature t equilibrate. Recrd the temperature f the water with the crrect number f significant figures and. Measuring Mass 1. Measure the mass f the fllwing bjects. Yu must recrd all significant figures frm the balance. This means measurements t g. If the numbers n the scale fluctuate, ask peple t mve away frm the scale and clse the drs t the lab if they are pen. Yur recrded measurement is the midpint f any fluctuatins that cntinue. a. Brand new #2 pencil b. 100 ml r 150 ml beaker c. 2-L sda bttle empty with cap Estimate the mass f yur lab manual. D nt measure it n the scale. Measuring Distance 1. Measure the fllwing lengths, in centimeters, using a meter stick, and recrd the measurements in yur datasheet with the crrect number f significant figures and. Recrd the measurement nly t the precisin that the instrument allws. On the meter stick the lines represent millimeters r 0.1 cm. Therefre, yur measurements shuld be recrded t the 0.01 cm. a. Yur height in centimeters b. The length f a new pencil c. The circumference f a 2-L bttle Estimate the width f yur lab drawer. D nt measure. Measuring Vlume Fr each f the 3 graduated cylinders, d the fllwing prcedure. 1. Determine the value f each increment in milliliters. 2. Read and recrd the vlume in milliliters fr each f the three graduated cylinders fund at the statins arund the labratry. Recrd the vlume frm the bttm f the meniscus. a. 100 ml graduated cylinder (t nearest 0.1 ml) b. 25 ml graduated cylinder (t nearest 0.1 ml) c. 10 ml graduated cylinder (t nearest 0.01 ml) Estimate the vlume f liquid in the displayed test tube. A meniscus as seen in a burette f clred water. '20.00 ml' is the crrect depth measurement. By PRHaney (Own wrk) [CC BY-SA 3.0 ( es/by-sa/3.0)], via Wikimedia Cmmns By PRHaney (Own wrk) 24

3 Part II Determinatin f Density & Identity f an Unknwn bject. Obtain an unknwn cubic slid frm the instructr labratry table. 1. T determine the density by the direct measurement methd, measure the mass using the labratry scale. Vlume by direct measurement Measure the length, width, and height f the cube in centimeters. Calculate the vlume by multiplying the length x width x height. Recrd yur measurements in yur datasheet and shw yur calculatins. Calculate the density f the cube (Equatin belw) dddddddddddddd = mmmmmmmm vvvvvvvvvvvv Vlume by displacement Take a graduated cylinder and fill it half way t a cnvenient vlume. Read the vlume f the water t the precisin f the graduated cylinder. Slwly slide the cube dwn the graduated cylinder being careful nt t splash the water t the side. Measure the new displaced vlume t the precisin f the graduated cylinder. Using the mass frm step1, calculate the density using this vlume measured by displacement. Recrd yur wrk and data in yur datasheet. Fr the Pst Lab Questins Identify yur unknwn based n the experimental density frm a list f pssible metals. Table f Pssible Unknwns Material Density (g/ml) ALUMINUM 2.70 BRASS 8.00 COPPER 8.90 STEEL 7.59 Calculate the percent errr frm yur experimental density frm the listed density f the metal yu have. eeeeeeeeeeeeeeeeeeeeeeee ttheeeeeeeeeeeeeeeeee % eeeeeeeeee = xx 100 ttheeeeeeeeeeeeeeeeee 25

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5 Experiment 3: Data Sheets Last Name First Lab Partner(s): Part I Metric Measurements & Estimates / pts Day aaaa. pppp. magnitude Temperature Length magnitude Mass Brand new #2 pencil 100 ml beaker 2-L sda bttle empty w/ cap Lab Manual * estimate** magnitude Yur height Brand new #2 pencil Circumference f 2-L bttle Lab Drawer width **estimate** Vlume 10 ml graduated cylinder 25 ml graduated cylinder 100 ml graduated cylinder Displayed test tube **estimate** magnitude 27

6 Part II Determinatin f Density & Identity f an Unknwn bject. UNKNOWN # Magnitude Mass Calculatin f Density Direct Vlume Length Width Height Vlume Density Vlume by Displacement Vlume initial Calculatin f Density Vlume Final Vlume Slid Density 28

7 Pst Lab Questins 1. Explain why the tw density values frm yur calculatins might be different. Inspect the number f significant figures fr each measurement and speculate which methd fr the determinatin f the vlume f the cube may be mre precise. 2. Based n the measured densities, identify the metal that yur cube is made f. Calculate the percent errr in yur measurement. Identity f Unknwn % Errr Mass Cnversins. D the fllwing cnversins fr the mass f the pencil. Cnversin factr: Cnversin factr: Cnversin factr: measurement frm part I mg = g g = kg lb = g milligrams kilgrams punds Pencil Beaker Shw yur calculatins fr the pencil with prper cancellatin. Circle yur answer. 29

8 Length Cnversins. D the fllwing cnversins fr the length f the pencil. Cnversin factr: Cnversin factr: Cnversin factr: measurement frm part I mm = cm m = cm in = cm millimeters meters inches Pencil Circumference 2L bttle Shw yur calculatins with the pencil prper cancellatin. Circle yur answer. Vlume Cnversins. D the fllwing cnversins fr the mas f the pencil. Cnversin factr: Cnversin factr: measurement frm part I ml = L ml = gal Liters gallns 10 ml graduated cylinder 100 ml graduated cylinder Shw yur calculatins fr the 100 ml graduated cylinder with prper cancellatin. Circle yur answer. 30