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

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UMD

CHEM 132

MIDTERM EXAM

STUDY GUIDE

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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find more resources at oneclass.com