Lab 1: sig figs & measurement of density

Objective

To learn the proper use of a top-loading balance, analytical balance, graduated cylinder, volumetric pipet, and thermometer; to understand the use of significant figures in measurements and calculations; to investigate the concepts of accuracy and precision; to determine the density of water, a solution, and a solid

safety

excessive force can cause glass to break when removing bulb on pipet

Degree of uncertainty in measurements

Implied range is +/- 1 of estimated digit

top loading

use when exact mass is less important or obtaining the mass of a liquid and its container 

analytical balance

If accuracy of mass is important, record to 4 decimal places

graduated glassware

calibrated to deliver or to contain the volume indicated at a specific temperature, usually 20 C

Beakers and flasks

not as accurate since markings are approximate

precision

how close measured values are to one another

accuracy

how close a measured value is to the theoretical value

percent error

statistical measure of accuracy

I theoretical – experimental I / theoretical

significant figures

indicate the precision of a measured quantity 

graduated cylinder

used to determine liquid volumes to the nearest 0.1 mL 

volumetric pipet

used to transfer accurate volumes of a liquid reported to 2 decimal places 

calibrated to deliver

precise volume is delivered to another container despite the fact that some liquid will remain  

calibrated to contain

volume transferred will be slightly less than indicated due to some remaining 

density

mass per unit volume of a substance