Name _________________________________ Class __________________ Date _________________________
EXPLORATION LAB
OBJECTIVE
Identifying an Unknown Substance
In this activity, you will perform several tests to identify unknown substances.
When chemists study chemical substances, they examine two types of properties:
chemical properties and physical properties. Some physical properties are extensive
properties, properties that depend on the amount of matter present. Mass and volume are
extensive properties.
Intensive properties, however, don’t depend on the amount of matter present. Color is an
intensive property. A large chunk of gold, for example, is the same color as a small
chunk of gold. The mass and volume of these two chunks are different (extensive
properties), but the color is the same.
Following are descriptions of the two types of properties:


Chemical properties: These properties enable a substance to change into a brandnew substance, and they describe how a substance reacts with other substances.
Does a substance change into something completely new when water is added —
like sodium metal changes to sodium hydroxide?
Physical properties: These properties describe the physical characteristics of a
substance. The mass, volume, and color of a substance are physical properties, and
so is its ability to conduct electricity.
• Identify an
unknown substance
by testing its
properties.
MATERIALS
For each group
• watch glass (2)
• 250 mL beaker
• scoop
• stirring rod
• unknown substance
(~2 g)
• vinegar, white
• water, room
temperature
For each student
• lab apron (optional)
• safety goggles
FORM A PREDICTION
Review the table below. Based on the information in the table, do you think
you will be able to identify ALL of the substances? Explain.
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Substance
A
B
C
D
E
Appearance
(crystals, powder, etc.)
Color
Solubility in water at
room temperature?
(yes/no)
Reactivity with
acid
(none, bubbles,
odor, etc.)
Density
Name _________________________________ Class __________________ Date _________________________
DEVELOP A PLAN
How will you test all of the properties listed in the table? What materials will you use?
Develop your procedure below.
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HAVE THE TEACHER APPROVE YOUR PLAN BEFORE MOVING TO STEP 4!
EVALUATE THE PLAN
Once your teacher has approved your plan, perform the steps you described in Step 3.
Record all your observations in the data table.
When you are done filling in the data table, get the substance chart from the teacher. The
chart will contain the name of all of the substances and their properties (THEY WILL
NOT BE IN ORDER!).
ANALYZE THE RESULTS
Analyzing Data
Based on the results of your tests, can you identify ALL your
unknown samples? If yes, what are they? If not, why are you unable to identify
ALL of them?
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Name _________________________________ Class __________________ Date _________________________
Evaluating Predictions
Review your prediction from step 1. Was your prediction
correct? Why or why not?
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DRAW CONCLUSIONS
Applying Concepts
According to the table, certain substances have similar appearances,
solubility, and reactivity with vinegar and oxygen. What further tests could you conduct to
distinguish between these substances?
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Classifying Observations
List each property of the unknown substances that you
observed during this experiment. Then, list whether the property is a physical property or a
chemical property.
Property
Physical or Chemical?
Synthesize Information
Why would it be useful to know the different
physical and chemical properties of substances?
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