1 Arizona State University School of Molecular SciencesHow is Lab Glassware Used?Introduction:In general chemistry lab, you will come into contact with common laboratory glassware,such as, beakers, Erlenmeyer Flasks, volumetric flasks, pipettes, burets, and graduatedcylinders. Beakers and Erlenmeyer flasks are usually to hold liquids throughout aninvestigation.When you look closer at each glassware, you’ll notice markings on eachmeasure specific volumes.Glassware is generally divided into two types, those thatholdcertain volumes and thosethatdelivercertain volumes.The purpose of this investigation is to find the most precise and/or accurate glasswarebased on the average lowest % error.Accuracyis the how close a measured value isto the actual (true) value.While,precisionis the repetition of measurements underunchanged conditions and shows the same results.The more precise and accurate ameasurement is, the less error with density calculations expressed, using significantfigures.Density(g/mL or g/cm3) is the substance is its mass (grams) per unit volume(mL or cm3), in other words,𝐷𝑒??𝑖?𝑦 =?𝑎???????𝑒Significant figuresare used as the number of digits that carry real information about ameasurement. There is no such thing as a perfect measurement.Which is why usuallyin an experiment, repeated trials are recorded to ensure verifiable data.The objective isto determine the relationship between percent error, and measurement accuracythroughout the experiment.Every lab equipment has some degree of uncertainty so you can estimate one moredigit past the smallest division on the measuring device. For example, for a 10mLgraduated cylinder the smallest graduation is tenth of a milliliter (0.1mL). That meanswhen you read the volume, you can estimate to the hundredths place (0.01mL).However, some glassware such as volumetric flasks and volumetric pipettes only havea single line to indicate volume. This is because they are made to measure just onespecific volume. In the case of the glassware used in general chemistry lab, both the10mL volumetric pipette and 50mL volumetric flask will have two sig figs after thedecimal point (i.e. 10.00mL and 50.00mL). For the 150mL beaker and the kitchenmeasuring cup, assume that 50.mL has two sig figs (it will not be obvious based on thevolume markings).
2 Arizona State University School of Molecular Sciences
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