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CHM 121 Lab 2 Report
- Course
- Chemistry 121
- Institution
- Harper College
This is a comprehensive and detailed lab report on lab 2; Measurement and Matter. *Essential!!
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Chemistry 100 LaboratoryLab 2: Measurement and Matter Lab
Introduction:
The purpose of this experiment is to help you learn about various measurement techniques and lab
apparatus. Measurements in the chemistry laboratory are made with equipment that varies in the degree of
certainty. In this lab, you’ll learn how to decide how many significant figures to use with each piece of
equipment (such as meter sticks, graduated cylinders, beaker, etc.). You’ll take measurements using both
English and Metric systems.
After this experiment you will be able to:
● measure length, volume and mass using various pieces of equipment from the lab and using the correct
number of significant figures
● make detailed observations
● identify the different classifications of matter
Materials:
150-mL beaker thermometer blue water stock
10-mL graduated cylinder ruler red water stock
50-mL graduated cylinder eraser yellow water stock
100-mL wide mouth copper(II)chloride 6 test tubes of the same type
graduated cylinder pieces of aluminum
Procedure:
Part I: Determining Significant Figures
1. Obtain a ruler, 150-mL beaker, 10-mL graduated cylinder and 50-mL graduated cylinder and
thermometer.
2. Look at the markings on each of these instruments: 150-mL beaker, 125-mL Erlenmeyer flask, 50-mL
graduated cylinder, meter stick, small metric ruler, analytical balance and thermometer. Fill out your data
table (an example is already done in the first row). To determine the appropriate number of significant
figures, record all certain digits and the first uncertain/estimated digit. If the equipment is digital, we use
all the digits shown. For English units of length, record values as a fraction, then convert to a decimal to two
places.
Note: you are not measuring anything here.
3. Use this table to ensure that you have the correct significant figures for all your measurements.
Verify with your instructor before you proceed that your table is correct.
Part II: Measurement of Mass
In our lab, we have an analytical balance. Never press on the balances!
They are very sensitive. Only put an object on the balance, if the lab asks you to. To
measure on a balance, simply brush the weighing pan clean with the balance
brush. Place a fresh piece of weighing paper or weighing boat (white plastic bowl)
on the weighing pan. Make sure the units are in grams, some balances can measure
in multiple units. Press the tare or zero button, this will zero out everything. Open
one of the doors and place your object on the weighing paper (or in the weighing
boat).
Close ALL the doors. Record ALL digits. This is the mass of your object. The purpose
of the weighing boat or paper is to keep from contaminating the balance or your sample. Always use a
weighing boat or paper or another clean small container (beakers or evaporating dishes work well too).
1
, A. Procedure for finding the mass of a small object by difference:
1. Pick a small object (ie. a coin, ring or paper clip; anything small to measure the mass of).
2. Press the “zero/tare” button to make sure the balance says “0.000 g”.
3. Gently place a weighing boat (white-hexagon shaped tray) on it. Record its mass to the correct number of
significant figures in your data table.
4. Do NOT tare/zero the balance again. Gently place the small object in the weighing boat record the new
total mass to the correct number of significant figures in your data table.
5. Subtract these two values to find the mass of the object.
B. Procedure for finding the mass of eraser directly:
There’s a quicker way to find mass of something if we don’t need the mass of the container it’s in.
Put a weighing boat on the balance and press “zero/tare”. Then, put the eraser in it and measure the mass of
the eraser. See the difference from above? Have one partner mass the eraser first. Then have the second
partner measure the mass of the same eraser. Sometimes you will see to "weigh" an object, you are really
determining it’s mass if the units are in grams. Record the mass of the object in grams (include all digits
shown on the balance). (How many places behind the decimal point?) See if both partners get the same
result. Keep the eraser at your desk. You will use the same eraser later on in the lab.
Part III: Measurement of Volume
A. Procedure for finding volume of eraser using a ruler:
1. Use the same eraser as before.
2. Acquire a ruler from the fume hood.
3. Take a 100-mL graduated cylinder and verify that your eraser slides nicely inside it before proceeding.
4. Measure the width, length and height of the eraser in CENTIMETERS. Be sure to record these values.
How many places should you include? Remember, generally, we estimate one decimal place past the last
marking on the measuring device. Note: it doesn’t matter what side of the eraser you call width, length or
height as long as you are consistent.
5. Measure the width, length and height of the eraser in INCHES. Record these values as well. If you
measure a fraction of an inch, convert it to a decimal with two places behind the decimal point.
For example, 1 ¼ inches would be written 1.25 inches.
6. Check that your significant figures match the data table you made in part I.
7. Keep the eraser at your desk. You will use the same eraser later on in the lab.
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