Lab Handout 2 - How is Lab Glassware Used Introduction In...

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1 Arizona State University School of Molecular Sciences How 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 graduated cylinders. Beakers and Erlenmeyer flasks are usually to hold liquids throughout an investigation. When you look closer at each glassware, you’ll notice markings on each measure specific volumes. Glassware is generally divided into two types, those that hold certain volumes and those that deliver certain volumes. The purpose of this investigation is to find the most precise and/or accurate glassware based on the average lowest % error. Accuracy is the how close a measured value is to the actual (true) value. While, precision is the repetition of measurements under unchanged conditions and shows the same results. The more precise and accurate a measurement is, the less error with density calculations expressed, using significant figures. Density (g/mL or g/cm 3 ) is the substance is its mass (grams) per unit volume (mL or cm 3 ), in other words, 𝐷𝑒??𝑖?𝑦 = ?𝑎?? ?????𝑒 Significant figures are used as the number of digits that carry real information about a measurement. There is no such thing as a perfect measurement. Which is why usually in an experiment, repeated trials are recorded to ensure verifiable data. The objective is to determine the relationship between percent error, and measurement accuracy throughout the experiment. Every lab equipment has some degree of uncertainty so you can estimate one more digit past the smallest division on the measuring device. For example, for a 10mL graduated cylinder the smallest graduation is tenth of a milliliter (0.1mL). That means when you read the volume, you can estimate to the hundredths place (0.01mL). However, some glassware such as volumetric flasks and volumetric pipettes only have a single line to indicate volume. This is because they are made to measure just one specific volume. In the case of the glassware used in general chemistry lab, both the 10mL volumetric pipette and 50mL volumetric flask will have two sig figs after the decimal point (i.e. 10.00mL and 50.00mL). For the 150mL beaker and the kitchen measuring cup, assume that 50.mL has two sig figs (it will not be obvious based on the volume markings).
2 Arizona State University School of Molecular Sciences

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