[CHEM 132] - Midterm Exam Guide - Ultimate 18 pages long Study Guide!

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UMD
CHEM 132
MIDTERM EXAM
STUDY GUIDE
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Experiment 1: Introduction to Measurement and Excel
-Purpose: The purpose of this experiment is to familiarize students with basic laboratory
measurement equipment to be used throughout this course, use Excel for the analysis and
presentation of data, distinguish between precision and accuracy, and apply rules of significant
figures when taking measurements.
-Vocabulary
systematic errors: errors arising from the imperfections of the instrument used to make the
measurement
random errors: errors arising from the skill or technique of the experimenter
accuracy: describes the closeness of a measured or experimental value to the theoretical
value (systematic)
precision: describes the closeness of two or more measurements to each other or the
repeatability of a set of measurements or results (random)
meniscus: curvature of liquids in glass containers
-Formulas
range = xmax - xmin
sd = (Σ(xi - ))/(n - 1)
absolute error = experimental value - theoretical value
percent error = (absolute error / theoretical value) * 100%
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Experiment 2: Identifying an Unknown Solid by Density
-Purpose: The purpose of this experiment is to carry out multiple measures of the volume and
mass of an unknown solid sample, construct a graph representing the independent and
dependent variables, interpret the slope of the data, and identify the unknown solid by its
density.
-Vocabulary
intensive property: depends only on the composition of the substance, does not differ with
the size or amount of substance being used
-Formulas
d = m/v or v*d = m
y = ax + b
slope = Δy/Δx = (v2 - v1)/(m2 - m1)
-Procedure
1. 2 unknown metal solids (5 samples each)
2. mass 1st metal *3
3. H2O graduated cylinder, record volume (V)
4. sample graduated cylinder
5. record ΔV, remove and dry sample
6. repeat 3-5 for 1st sample
7. repeat 2-6 for 2nd sample
8. return samples
-Graphs
mean volume (mL)
mean mass (g)
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