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MEASUREMENTS, CONVERSIONS AND DENSITY Purpose: In this experiment you will become familiar with some basic laboratory equipment and measurements. You will also become familiar with the Metric System and calculate density. Materials: Meter stick, Calculator, Balance, Wooden Blocks. Introduction: A laboratory balance is used to obtain the mass of a wooden block. The balance is simple to use, delicate and expensive. There are several different kinds of balances used, so the selection depends on the precision required. The meter (m) is the standard unit of measurement for length. The meter stick is divided into centimeters (1 cm = 0.01 m; 1m = 100 cm) and millimeters (1 mm = 0.001m; 1 m = 1000mm). Density is a physical property that can be observed without altering the composition of a substance. Some physical properties enables us to identify and distinguish it from other substances. Useful conversion factors: 1 lb = 453.6g 1 inch = 2.54 cm PROCEDURE It may be helpful to review SIGNIFICANT FIGURES Work in pairs or small groups A. Measurements 1. Obtain one of the wooden blocks and record it's number and density as listed on the block. 2. Study your ruler and evaluate the least distance between any two adjacent lines. This is called the least count. A good scientist (or student) will guess/estimate the distance between these lines to 1/4 to 1/5 of the least count. What is the least count on the ruler? ____________ 3. Take turns in measuring the sides of the wooden block and obtain an average for length, width and height. Each student should obtain a reading for the block and obtain an average measurement. B. Mass Measurements 1. To make mass measurements use the mass balance. Study the divisions on the balance. What is the least count on the balance? __________ 2. Obtain a balance and see if when empty it balances to zero. If it will not balance at zero obtain an "empty reading" to be subtracted from the final reading. Each student should obtain a mass value for the block and obtain an average mass. If you need help, ask your instructor. 3. Each student should obtain a mass value for the block and obtain an average mass Name_____________________ _____________________ _____________________ _____________________ _____________________ Date _____________________ MEASUREMENTS, CONVERSIONS AND DENSITY REPORT SHEET Listed density____________lb/ft3 Block #__________ Least count on the metric ruler __________ Least count on the balance _____________ Length___ Height ________cm ________ ________ ________ ________ ________cm ________ ________ ________ ________ Average ________cm ________cm Width Mass ________cm ________ ________ ________ ________ ________ ________cm ________g ________ ________ ________ ________ 1) Calculate the VOLUME = L x W x H a) in centimeters (using a calculator) __________ (units?) 2) Calculate the density = __________ (units?) 3) Convert the mass in grams to English pounds ________ 4) g equals ________g lb Convert the volume from cubic centimeters to cubic feet ________ cc ft3 equals 5) Calculate the density in 1b/ft3 6) Compare the calculated density to the value listed on the block 7) Calculate your percent error % Error = I calculated density - listed density I ________ listed density x 100