ACTIVITY B1
Properties and Interactions of Chemical
Substances
Experiment day 1: Part I Chemical Substances – Properties and
Processes
Experiment day 2: repeat Part I with second substance
Pre lab check list
c Read through procedures
c Write prelab assignment in lab notebook
1. Title
2. Purpose
3. Chemical equations
4. Chemicals safety table
5. Safety precautions
6. Waste disposal
7. Pre-lab questions
8. Procedure summary with appropriate data tables
c Complete the pre-lab quiz (as directed by instructor)
c Pack your PPE and wear appropriate lab attire
Act B1 PCC-SI Properties and Interactions of Chemical Substances
How do we know that a process is a chemical or physical change? Scientists collect and analyze data to
support claims made about the type of change. Before data can be analyzed, they must be properly
collected and recorded so that experiment findings can be replicated and verified by other scientists.
The goal of this activity is to develop skills to collect and record data measured using different types of
equipment in the laboratory. You will examine two processes: heating substances and dissolving them in
water. You will analyze data to determine whether a physical or chemical change occurred. You will
explore these processes from a macroscopic view that can be seen with the naked eye and a particulate
view at the level of atoms and molecules.
Learning Outcomes
At the end of this laboratory activity you will be able to:
Technical skills: demonstrate appropriate use of equipment to obtain samples and measure mass,
volume and temperature
Data skills:
record data with appropriate variables names, significant figures and uncertainty,
organize data in a lab notebook
Modeling skills: identify components used to represent particles in a substance
Techniques:
handling chemicals, volume measurements, use of analytical balance,
use of Bunsen burner
Equipment:
From your locker – test tubes, beakers, graduated cylinder, thermometer, wire
triangle
From the bench top – ring stand
From shared equipment drawers – Bunsen burner, iron ring
From the instructor – crucible
Chemicals:
Solids
Liquids
potassium chlorate, potassium chloride
deionized water
Waste Disposal: All solutions can be disposed in the aqueous waste containers. Excess solid can be
disposed in the solid waste containers. Additional disposal instructions may be provided by your
instructor.
Procedure: Each student will collect data on 1-2 of the solid chemicals, as assigned by the laboratory
instructor. Collect data for one chemical before beginning data collection for another chemical. The
procedures for data collection used during each step are described after the following table.
Section Data Collection Procedures
Part I
Notes
Step 1: Describe physical
properties
Reduce waste! Do not take more chemical than indicated in
the procedure. Be sure to close all containers after use.
Step 2: Heat Substance
During Step 3 you will interact the residue from Step 2 with
water. You should use the same amount of the original
substance with water in order to compare data.
Step 3: Interaction with
Water
IMPORTANT Procedure Notes
There are a few key steps in this procedure that you need to complete. To make sure you are aware of
these steps, read the procedures for this activity and answer the following questions. Your instructor may
require you to submit the answers to these questions in your lab notebook at the start of the lab activity.
For each of the following questions, select all answer options that apply.
Pre-lab questions
Ques 1. In step one, how much of the solid chemical should
you obtain?
c between 0.10 and 0.40 grams
c approx. the size of a quarter
c size is provided by your lab instructor
Ques 2. In step two, the flame temperature used on the
Bunsen burner should be at a:
c very high temperature
c between medium to high temperature
c low temperature
Ques 3. The substance should be heated using a Bunsen
burner at least:
c two minutes
c five minutes
c ten minutes
Ques 4. The substance should be heated, cooled, and then
weighed:
c until you cannot see any changes
c at least two times
c until the mass of residue after heating
remains nearly constant
Ques 5. In step three, how much of the solid chemical should
c between 0.10 and 0.40 grams
you interact with water?
c approx. the size of a quarter
c size is provided by your lab instructor
Ques 6. What measurements should you obtain on the
substance once it is mixed with the water?
c temperature of the interaction
c mass of water
c solubility of the substance in water
Part I: Chemical Substances - Properties and Processes
1. Describe physical properties
In this step you will obtain a sample of a substance (as assigned by your instructor) and then measure and
record its physical characteristics.
If you spill any chemical on yourself, wash at the nearest sink and inform your instructor. Dispose of
spilled or excess chemicals as directed by your instructor.
a. You first need to obtain a sample of the solid chemical substance in an appropriate container (e.g., a
plastic weighing boat). The size of the sample is assigned by your instructor.
When you remove a solid chemical from a bottle, you should take care to avoid contamination of
your sample and the substance in the bottle. Be sure to properly label your sample and clean up
any mess if the chemical is spilled - never return substances back into the original chemical bottle.
b. Now that you have your sample, describe its physical characteristics. Be descriptive! In addition to the
color of the sample, other observations can include the texture (powder versus glass-like crystal),
and the size of the particles. You can also compare it to something you know (e.g., looks like
sugar).
2. Heat Substance
In this step you will heat a sample of a substance and then measure and record any changes in
appearance or mass.
You will use a Bunsen burner with a medium to high temperature flame to heat the substance.
Your instructor will show you how to use a Bunsen burner and the safety precautions you should follow,
such as not having loose paper nearby.
You will use a balance to measure the mass of the substance. Your instructor will show you how to use
the mass balance. Always weigh a substance while it is in a container - you should never place a chemical
substance directly on the mass balance.
a. You first need to determine the mass of the substance before you heat it. Because the substance will
be heated in a crucible, you can use this container to determine the mass of the substance.
Measure the mass of an empty dry crucible. You then need to use a spatula
to transfer approximately half of your sample of the substance to the crucible
and reweigh. This method of determining the mass of the substance is called
‘weigh by addition’. Calculate the mass of the substance by subtracting the
mass of the empty crucible.
b. You will use a Bunsen burner as shown in the apparatus set up in Figure 1 to heat
the substance. Light the Bunsen burner and adjust the air flow until you have
a medium to high temperature flame.
Figure 1
Heat the substance in the crucible for five minutes. Before you weigh the crucible and its contents,
you need to let the crucible cool for at least five minutes. Place the hot crucible in a safe location
to cool, such as on the metal part of the ring stand or using an inverted clay triangle. Be sure you
always use crucible tongs to move the crucible. Use a Petri dish or large beaker to transport the
crucible to measure mass, when it is cool.
c. You now need to determine the mass of the substance after heating (the ‘residue’) by measuring the
mass of the crucible and its contents after it is cool. Calculate the mass of the residue by
subtracting the mass of the empty crucible. You should also describe the physical characteristics
of the residue in the crucible both during and after heating.
d. You need to continue reheating the substance until it reaches a ‘constant mass’ - this is an indication
that the process of heating the substance is complete and no further changes are observed in the
mass data. For each heat-cool-weigh cycle, you should record the mass of the crucible plus residue
and observations of the residue.
Sample Data Table
Contents
Empty crucible
Crucible with substance before heating
Crucible with substance after 1st heating
Crucible with substance after 2nd heating
Mass (g)
3. Interact Substance with Water
In this step you will interact substances with water and then measure and record any changes in
appearance, temperature, and solubility.
The solutions created by these substances in water are potentially corrosive and toxic with repeated
exposure. If contact should occur, flush the area with plenty of water.
a. Fill a small beaker approximately half-full with deionized water. Use a thermometer to measure the
temperature of the water in the beaker.
b. You need to obtain a sample within a given mass range before you add water to the substance. Use a
spatula to transfer a portion of the heated residue (¼, ½, or ¾ - as directed by your instructor)
from the crucible to a clean, dry test tube. The test tube must be able to hold a volume of at least
10 mL. Reweigh the crucible and its contents in order to calculate the mass of residue removed.
This method of determining the mass of residue transferred to the test tube is called ‘weigh by
subtraction’.
c. You need to measure out a 5.0-mL sample of deionized water from the beaker using a 10-mL
graduated cylinder. The procedure that minimizes contamination is to first pour water from the
beaker until the volume is within 1 mL of the desired volume. Next, use a clean disposable pipet
(or medicine dropper) to add water to the graduated cylinder until the bottom of the meniscus is
on the 5.0-mL mark.
d. Pour the 5.0 mL of deionized water from the graduated cylinder into the sample of residue in the test
tube and then immediately use a thermometer to monitor the temperature of the interaction
between the solid substance and water for 1-2 minutes. Gently mix the solution using the
thermometer. Measure the highest or lowest temperature of the solution during the interaction.
You should also describe the physical characteristics of the interaction of the residue with water.
e. To determine the solubility of the residue in water, examine the contents of the test tube after mixing
the solution for at least 2 more minutes. Observe the characteristics of the solution and classify
the solubility of the residue using the scale in Table 1.
Table 1. Solubility scale
Solubility
Description
f.
Soluble
All of the solid has dissolved
Nearly
Soluble
A large fraction of the solid has dissolved, but a
small amount of the solid remains in the solution.
Somewhat
soluble
Some of the solid has dissolved, but a large
amount of the solid remains in the solution
Insoluble
Most (or all) of the solid did not dissolve
To compare the data collected on the residue and the original substance, you will need to use the
same procedure to interact a similar amount of the original substance with water and measure
the same properties of temperature and solubility. For example, if you used 12 g of the residue,
you should aim to use about 12 g of the original substance. To minimize contamination, be sure
to clean the spatula between transfers of the different substances. Your instructor may also
require you to repeat the experiment using different amounts of the substances.
Sample Data Table
Substance
Original
Residue
Mass (g)
Highest/lowest
temperature (C)
Skill Development Questions
Check with your instructor as to which questions you need to complete each day in lab. Record your
answers to each question in your laboratory notebook.
Skill Development #1 – Assigning Variable Names
Each of the properties you observed can be described by different variable names. A variable name should
indicate two things: 1) the type of property being observed, and 2) the object being measured. You should
always use appropriate and complete variable names to describe the data collected in lab.
In the following, examples of appropriate variable names are provided for the two types of data you
collected in lab, qualitative and quantitative. Quantitative data typically involve a numerical measurement
to indicate the amount or quantity of a property. Qualitative data involve comparisons based upon
qualities of properties and do not typically involve a numerical component.
Sample Variable Name for Qualitative Data
Variable name: Color of KCl(s)
This is an appropriate variable name that describes both the property being observed, the color;
and the object, a sample of solid potassium chloride.
Sample Variable Name for Quantitative Data
Variable name: Mass of crucible
This is an appropriate variable name that describes both the property being measured, the mass,
using a balance; and the object, a crucible.
Sample Inappropriate Variable Name for Quantitative Data
Variable Name: Volume in mL
This is not an appropriate and complete variable name. It does describe the property being
observed, namely the volume, but it does not indicate the object. The volume of what substance
is measured? The unit of the property measured, in this case milliliters, should be associated with
the data value and not the variable name.
Provide appropriate variable names for at least two of the properties of the solid chemical substance you
observed during lab. Record these variables names in your laboratory notebook.
Skill Development #1 - Record in your lab notebook
Variable Name 1: ______________________________________
Variable Name 2: ______________________________________
Skill Development #2 - Determining Uncertainty in Measured Values
Most quantitative data that you record should include the uncertainty in the measurement. This
uncertainty reflects both the error in the equipment itself and also the error from your
use of the equipment.
For example, most 50-mL graduated cylinders have a smallest increment of 1 mL. In this
case, the error in volume measurements based on the instrument is a maximum
fluctuation of ± 1 mL and the uncertain digit in the data value is in the ones place.
Determine the maximum uncertainty in volume for two different-sized graduated
cylinders. The largest value for the uncertainty in the volume measurement is based on the smallest
increments on the scale (i.e., the ‘tick’ marks) of the graduated cylinder.
Skill Development #2 - Record in your lab notebook
(Indicate the sizes of graduated cylinders selected)
⎕ 10-mL graduated cylinder
Maximum uncertainty: _______mL
⎕ 50-mL graduated cylinder
Maximum uncertainty: _______mL
⎕ 100-mL graduated cylinder
Maximum uncertainty: _______mL
Skill Development #3 - Determining Number of Significant Figures for a Data Value
Most labs have a centigram balance that can measure the mass of a substance to the hundredths decimal
place. For this instrument, the uncertainty in mass would be ±0.01 g. Your lab may also include an
analytical balance that can measure mass to the thousandth or beyond the thousandth decimal place.
When you record quantitative data values, you need to determine how many significant figures to include.
The number of significant figures in a data value is related to the uncertainty of the instrument used to
make the measurement. For a centigram balance with an uncertainty in mass of ±0.01 g, the uncertain
digit is in the hundredths decimal place. If the mass of an object is measured on this balance, the data
value can be reported only to the hundredths decimal place.
Suppose that an object with a mass of exactly 1 gram and is weighed on two different mass balances. For
each measurement of the mass of the object, provide the appropriate quantitative data value that can be
reported.
Skill Development #3 - Record in your lab notebook
Mass of object (centigram balance): _________________
±0.01 g
Mass of object (analytical balance):
±0.0001 g
_________________
ACTIVITY B.1 CHEM120A
Mass Assignments
Front of classroom: White board
Step 3b ¼ of residue
Step 3b ¼ of residue
Step 3b ¼ of residue
Step 3b ¼ of residue
BENCH 1
Step 3b ½ of residue
Step 3b ½ of residue
Step 3b ½ of residue
Step 3b ½ of residue
Step 3b ¾ of residue
Step 3b ¾ of residue
Step 3b ¾ of residue
Step 3b ¾ of residue
BENCH 2
Step 3b ½ of residue
Step 3b ½ of residue
Step 3b ½ of residue
Step 3b ½ of residue
Step 3b ¾ of residue
Step 3b ¾ of residue
Step 3b ¾ of residue
Step 3b ¾ of residue
BENCH 3
Step 3b ¼ of residue
Step 3b ¼ of residue
Step 3b ¼ of residue
Step 3b ¼ of residue
Act B1 PCC-SI Interim Assignment
Directions:
The purpose of this assignment is to help you develop skills for recording quantitative data and for
organizing and manipulating data in spreadsheets.
All data collected in a lab needs to be recorded such that another person can quickly determine what
measurements were performed. All quantitative (numerical) measurements are recorded using the
following four components: 1) a variable name, 2) a data value, 3) an uncertainty, and 4) a unit.
Variable
Name
A variable name should indicate two things: a) the type of property being
observed, and b) the object being measured.
Data Value
When you record quantitative data values, you need to determine how many
significant figures to include. The number of significant figures in a data value is
related to the uncertainty of the instrument used to make the measurement.
Uncertainty
Most quantitative data you record should include the uncertainty in the
measurement. This uncertainty reflects both the error in the equipment itself
and also the error from your use of the equipment. In general, the largest value
for the uncertainty in a measurement is based on the increments on the scale
(i.e., the ‘tick’ marks) on the equipment.
Unit
The unit of measure depends on the property and the instrument used to
measure the property. In this laboratory the gram was used as a unit of mass,
the mL was used to measure the volume of water and 0C was used to measure
temperature.
For example, a centimeter ruler that has a 0.1 cm scale to measure the length of a cylinder.
Variable Name Data Value ± Uncertainty Units
Length of cylinder 10.5
±
0.1
cm
The variable name, length of cylinder, is an appropriate variable name that describes both the property
being observed, length; and the object, a cylinder. The data value, 10.5, has a total of three significant
digits. The doubtful digit in this measurement, the “5” in the tenths place, is because the uncertainty in
the measurement is in the tenths place, 0.1 cm. A data value can only be recorded to the same decimal
place as the uncertainty of the measurement.
You observed the behavior of ionic solids when dissolved in water in Step 3 of this lab activity. As
part of the data collected, you measured the temperature of the solution formed when the solid
interacted with water. Use the information provided in the illustration above to record the four
components of quantitative data for this temperature measurement.
Variable Name
Data Value
Uncertainty
Units
How many significant figures are in the data value you recorded?
For data collected across multiple students, we need to have a consistent structure for how these
data are recorded. In most cases, you will use a data table to record repetitive data. A single column
in a data table is be a summary of the data values for a repeated measure.
For example, the first column in the table below is a summary of the data collected across several
samples for the mass of the crucible. The first row of a data table is used to record information about
each measurement - this is called the header row of a table.
Mass of Crucible (±0.01 g)
Color of KCl(s)
18.32
white
17.59
white
[Column Header]
[Column Header]
For quantitative data, the header identifies the variable name, uncertainty and unit of measure for
all of the data values that will appear in that column (e.g., Mass of Crucible (±0.01 g)). For qualitative
data, the header consists of the variable name (e.g., Color of KCl(s)). Below the header, data values
are recorded with an appropriate number of significant figures and no units. Units are contained in
the header, so it is not necessary to repeat them for each individual measurement.
In this lab activity you made several repeated measurements that resulted in both quantitative and
qualitative data. Provide three examples of a header using the quantitative data you collected during
the lab activity.
[Header #1]
[Header #2]
[Header #3]
You will use an Interim Group Data File to complete the following tasks. Your instructor will provide
details on where to access this group data file. This file contains a reduced set of data collected by
students in a previous semester. This data file has three “tab” worksheets that are labeled as “Step
1”, “Step 2”, and “Step 3”. The tabs are located at the bottom of the spreadsheet window.
One important method of organizing data for analysis is to sort it. A table in a spreadsheet can be
sorted according to different criteria that are based on data in each column. Copy and paste the URL
below into an Internet browser to view a tutorial on how to sort data in an Excel spreadsheet.
URL: http://youtu.be/1-QKOolDfg8
Analysis of Step 1 Data: Describe Physical Properties
You will sort the data file using the information in the header row. Sort the data from the tab labeled
"Step 1” by the following single criterion: Alphabetical order by “Substance Name”
Once the data has been sorted, you can now determine the number of data sets (i.e., rows of data
below the header row) that exist for each type of substance investigated.
Potassium Chloride - Number of Data Sets
Potassium Chlorate - Number of Data Sets
Analysis of Step 2 Data: Heat a Substance
For the following questions, use the data from "Step 2: Heat Substance" in the Interim group data
file.
Sort the data from Step 2 by the following two criteria:
Criterion #1:
Criterion #2:
Alphabetical order by “Substance Name”
Descending numerical order by “Mass of Substance before Heating”
For the substance potassium chlorate, identify the largest data value for “Mass of Substance before
Heating” using the data from Step 2.
Mass of Substance Before Heating
Calculate the change in mass upon heating for the largest data value for “Mass of Substance before
Heating” for potassium chlorate where the following formula is used to calculate change in mass on
heating. (You may calculate the value “by hand” or use a formula in Excel to determine the
difference.)
Change in Mass on Heating = Mass of Substance - Mass of Residue
Mass of Substance before Heating
(±0.0001 g)
Mass of Residue after
Last Heat (±0.0001 g)
(Step 2 Data)
Change in Mass upon
Heating (g)
The value calculated for change in mass upon heating cannot be directly compared across different
samples because they each started with a different initial mass before heating. Using a percent scale
is one way to compare values across samples by imposing a common scale of parts per 100.
Calculate the percent change in mass upon heating for the same sample of potassium chlorate used
above. (You may calculate the value “by hand” or use a formula in Excel to determine the change in
mass in percent.)
Percent Change in Mass on Heating = [(Mass of Substance - Mass of Residue)/(Mass of Substance)] x 100
Mass of Substance before
Heating (±0.0001 g)
Mass of Residue after Last Heat
(±0.0001 g)
Percent Change in Mass
upon Heating
You can now calculate the percent change in mass upon heating for ALL samples of potassium
chlorate heated in Step 2. While you may perform these calculations by hand, it is easier and there
will be fewer calculation errors, if formulas are written in the spreadsheet.
In the table below, data from Step 2 for the two smallest masses of potassium chlorate before
heating are provided. In column D, a formula can be entered into the cells to calculate the change in
mass upon heating. To enter a formula, start with the equal sign and then use cell references to point
to the data values that are part of the calculation. For example, in cell D2 the change in mass is
calculated by subtracting cell C2 from cell B2.
A
B
C
D
E
1
Substance
Name
Mass of
Substance
Before Heating
(g)
Mass of Residue
After Last Heat
(g)
Change
in Mass
upon
Heating
(g)
Percent
Change in
Mass upon
Heating
2
Potassium
chlorate
0.1289
0.1273
=B2-C2
=D2/B2*100
3
Potassium
chlorate
0.1646
0.1620
=B3-C3
Instead of writing a formula several times down a column, you can write the formula in one cell and
copy it to other cells. When you select a cell, it is highlighted and usually contains a small square in
the lower right corner of the cell. To copy the formula in that cell, use the cursor to select the small
square in the lower right corner and move the cursor down to other cells. The cell references in the
formula will automatically change for each new row.
Copy and paste the URL below into an Internet browser to view a tutorial on how to copy a formula
in an Excel spreadsheet. URL: http://youtu.be/UTXzIKvTdGw
In the Interim Group Data file, use formulas to calculate the percent change in mass upon heating for
all samples of potassium chlorate. The percent change in mass data values are now all on the same
scale (from 0-100%) and comparisons can be made across the samples.
You can now write a formula to calculate the average percent change in mass on heating over all of
the samples of potassium chlorate data from Step 2. Copy and paste the URL below into an Internet
browser to view a tutorial on how to write the formula for an average in an Excel spreadsheet.
URL:
http://youtu.be/EJa28DIaJKI
Step 2: Average Percent Change in Mass upon Heating (KClO3)
Analysis of Step 3 Data: Interact a Substance with Water
For the following questions, use the data from "Step 3: Interact Substance with Water" in the Interim
group data file.
Sort the data from Step 3 by the following two criteria:
Criterion #1: Alphabetical Order by “Substance Name”
Criterion #2: Descending Order by “Mass of Residue”
For potassium chlorate, determine the total number of rows of data in the file. You may choose to "hand
count" the number of rows of data for potassium chlorate, but it is easier to use existing functions in
Excel to complete this task. By selecting the range of cells that you wish to count, Excel will provide
summary statistics in the lower right hand corner of the spreadsheet. These statistics usually include the
functions COUNT, AVERAGE, and SUM.
Copy and paste the URL below into an Internet browser to view a tutorial on how to count rows of data
in an Excel spreadsheet.
URL: http://youtu.be/rQbjWcxiD10
Within this complete set of data for KClO3, determine the number of rows of data that fall within the
mass range of 0.00 to 0.30 grams for "Mass of Residue".
Step 3: Number of rows of data (KClO3)
Step 3: Number of rows of data with "Mass of Residue" values from 0.00 to 0.30 grams (KClO3)
During lab you measured the solubility of the residue in water by using a qualitative rank scale that
classified solubility as one of four options:
Soluble - all of the solid dissolved
Nearly Soluble - a large fraction of the solid dissolved, but a small amount remains in solution
Somewhat Soluble - some of the solid dissolved, but a large amount remains in solution
Insoluble - most of the solid did not dissolve
For the subset of KClO3 data that have a “Mass of Residue” values ranging from 0.00 to 0.30 grams,
determine the frequency (i.e., the number of data rows) with which each option for solubility
occurred. Note that you may want to sort the data by an additional criterion, "Solubility of Residue",
in order to more easily complete this task.
Soluble – Frequency
Nearly Soluble – Frequency
Somewhat Soluble – Frequency
Insoluble – Frequency
Which solubility option occurred with the highest frequency for these samples of KClO3 residue that
had a mass in the range of 0.00 to 0.30 grams?
Circle one:
Soluble
Nearly Soluble
Somewhat Soluble
Insoluble