Title: Lab: Distinguishing Among Substances
Author : David Wright
Subject Area(s): Physical Science
Grade(s): 9th grade
Description of Lesson: This is a laboratory activity in which students will use physical and
chemical properties to identify an unknown substance based on the properties of several known
substances.
Length of Lesson: 2 class periods
Student Objectives:
1. Define what a physical property of matter.
2. Define chemical property of matter.
3. Differentiate and between and identify unknown substances based on their physical and
chemical properties.
Materials: For each group you will need
 4 containers of white powder labeled “W”, “X”, “Y”, “Z”
 5 sheets of colored paper labeled “W”, “X”, “Y”, “Z”, and “M”
 Magnifying glass
 5 clear containers each holding 100 ml of warm water and labeled “W”, “X”, “Y”, “Z”,
and “M”
 5 stirring rods
 Mystery vial of white powder
 Test solutions of water, vinegar, iodine and phenolphthalein solutions with eyedroppers
(for part B)
 Spot plate (for part B)
You will also need a web cam or flex cam with computer and projector for the followup
discussion to this lab.
Procedure:
1. Prepare labeled (W, X, Y, Z) containers of corn starch, baking soda, salt, and powdered sugar.
Make a key as to which container contains which substance. Do not tell the students what the
substances are at this time. Make another set of containers labeled M. These contain the
unknown mystery substance, which in this case will be powdered sugar.
2. Have the students conduct the Lab - Distinguishing Substances. This should take the hour.
They can finish the discussion questions for homework if need be.
3. Lead the students in a discussion the next day as to what the mystery substance was. What
clues did they use to determine its identity. Use a web cam or better yet a flex cam hooked up to
the computer and a projector to show samples of the powders on the screen. Select a different
mystery substance (starch instead of powered sugar) this time. Conduct some of the tests the
students completed and have then lead you through a procedure of how to decide what the new
mystery substance would be.
Scientific Explanation: Scientists are in the business of observing, comparing and classifying
things in their quest to figuring out the wonders of the universe. Basic observation skills are
needed if inferences are to be made as to the identity of unknown things.
Assessment: Present students with a data table of observations of 5-6 substances and an
unknown. Have them identify which if any of the substances the unknown would be based on the
information in the data table.
Kansas Science Standards:
Standard 1 Science as Inquiry, Benchmark 1: The student will demonstrate abilities necessary to do the
processes of scientific inquiry.
Standard 1Science as Inquiry, Benchmark 3: The students will analyze how science advances through
the interactions of new ideas, scientific investigations, skepticism, and examinations of evidence of varied
explanations.
Standard 2 Physical Science, Benchmark 1: The student will observe, compare, and classify properties of
matter.
Missouri Science Standards (GLE’s):
Strand 1Properties and Principles of Matter and Energy.1, Concept A Objects and the materials they are made of,
have properties that can be used to describe and classify them.
Strand 7 Scientific Inquiry.1, Concept C Scientific inquiry includes evaluation of explanations
(laws/principles/theories/models) in the light of evidence (data) and scientific principles (understandings).
Name_______________________________________
Date__________ Class______
Teacher __________________
Lab: Distinguishing Among Substances_________________
Materials
 4 containers of white powder labeled “W”, “X”, “Y”, “Z”
 5 sheets of colored paper labeled “W”, “X”, “Y”, “Z”, and “M”
 Magnifying glass
 5 clear containers each holding 100 ml of warm water and labeled “W”, “X”, “Y”, “Z”,
and “M”
 5 stirring rods
 Mystery vial of white powder
 Test solutions of water, vinegar, iodine and phenolphthalein solutions with eyedroppers
(for part B)
 Spot plate (for part B)
Purpose
To determine the differences among substances that look very much alike.
Procedure
Part A – Physical Properties
1. Pour a small amount of substances from the vial marked “W” onto the sheet of colored
paper labeled “W”
2. Examine the substance with a magnifying glass. Note the size and shape of particles.
When describing size it is helpful to refer to things like sand, a period on a page, etc.
When describing shape not if it is crystalline (regular pattern) or irregular (has no
repeating pattern, no definite shape).
3. Rub a small amount of the substance between your fingers. Observe the texture.
SAFETY NOTE: Do not taste any of the substances. Unknown substances may be
poisonous and may taste like sweaty hairy people.
4. Using the same procedure, test each of the other substances. Note carefully all your
observations about each substance in the table on the activity record sheet.
5. Pour about half of the substance out of vial “W” into 100 ml of warm water. Stir with a
clean stirring rod.
6. Carefully note the color, odor, and clarity (clear vs. cloudy) of the liquid.
7. Use the same procedure to test the other three substances. Be careful to match the labels
on the paper, vials, and beakers with each other. Use clean water each time for each test.
Carefully note your observations.
8. Repeat the entire testing procedure with the mystery substance. Carefully note the results
of each test. Compare these results of each test. Compare these results with the results
for the other substances you tested.
Part B -Chemical Properties
9. Place a sample about the size of a pea of each sample in its own well on the spot plate.
Make note which substance is in which well. Drop 3-5 drops of water on each substance
and records the results.
10. Clean the spot plate and repeat for each test solution. Be sure to clean the stop plate and
place fresh samples in the well for each chemical test.
Observations
As you conduct this activity, record your observations in the table provided below.
Data Table for Part A – Physical Properties:
Dry
I
n
Substances
H
o
t
W
a
t
e
r
Size
Shape
Texture
Color
Odor
W
X
Y
Z
M
(mystery)
Data Table for Part B – Chemical Properties:
Chemical Test
Substances
Water
Vinegar
Iodine Solution
Phenolphthalein
Solution
W
X
Y
Z
M
(mystery)
Questions
1. Did all the substances look the same when magnified? If not describe their differences.
________________________________________________________________________
_______________________________________________________________________
Clarity
2. Which of the substances has a noticeable odor when dry? ________________________
When mixed with water? ________________________
3. Which of the substances disappears when put in water and stirred? __________________
4. Which of the substances causes the water to become cloudy? ______________________
5. Which of the substances fizzed in presence of the vinegar? ________________________
6. Which of the substances turned black with the iodine test? ________________________
7. Which of the substances turned red with the phenolphtalein? ______________________
8. Did any of the substances react with water? ____________________________________
9. Which other properties, besides those listed in the data table, could be used to describe
each of the substances? ____________________________________________________
_______________________________________________________________________
10. Why do you think this happens (hint, what kind of mixture do you think it forms)?
________________________________________________________________________
______________________________________________________________________
11. In which of the vials are the test results the same as in the mystery vial? ______________
12. What observations allowed you to make your conclusion as to which substance was the
same as the mystery substance? ______________________________________________
___________________________________________________________________________
__________________________________________________________________________
Conclusion: What are some of the methods you can use to determine the different properties
of substances that look very much alike?
___________________________________________________________________________
_________________________________________________________________________
___________________________________________________________________________
__________________________________________________________________________