Name:
_________________________
Date: _______________
Period: _____
The Mystery Powders Lab: Physical and Chemical Changes
Background Information: You have learned how to describe matter based on its
physical and chemical properties. You have also learned some clues that tell you
whether a physical change or a chemical change is occurring. A physical change
does not change a substance’s identity. A chemical change produces a new
substance that was not there before—like CO2 gas and may be indicated by
any of the 4 signs of a chemical change.
Your objective in this lab experiment will be to determine the identities of four
similar looking powders by placing different liquids on them and observing a
physical property, solubility and the chemical property of reactivity. You will
be able to tell if a chemical change is occurring by looking for the 4 signs.
Question: What are the identities of four “mystery powders” that are similar in
appearance? (Baking Powder, Baking Soda, Powdered Sugar, and Cornstarch)
Hypothesis (from visual observation): Powder A= __________Powder B= ______
Powder C= _________Powder D= ______
Materials:
Procedure:
1. Using the appropriately labeled spoons, scoop up a tiny bit of the following
powders and place them in the indicated wells in the spot plates:
Note: Be careful NOT to cross-contaminate!
2.
3.
4.
5.
6.
Powder “A” and place it in wells 1, 5, and 9 Use the “A” spoon!
Powder “B” in wells 2, 6, and 10. Use the “B” spoon!
Powder “C” in wells 3, 7, and 11. Use the “C” spoon!
Powder “D” in wells 4, 8, and 12. Use the “D” spoon!
Use an eyedropper to add water into the wells 1, 2, 3, 4 so that it fills
most of the well. Stir each well with a clean toothpick. Do not reuse.
7. RECORD YOUR OBSERVATIONS IN THE DATA TABLE.
8. Use the dropper in the vinegar bottle to add 10 drops of vinegar to the
powder in wells 5, 6, 7, 8. Stir with a clean toothpick for each well and
record observations.
9. Use the dropper in the iodine bottle to add 10 drops of iodine to well 9,
10, 11, 12. BE CAREFUL BECAUSE IODINE WILL STAIN. Stir with a
new toothpick for each test. Record observations.
10. Did you RECORD ALL OBSERVATIONS??? Double check to make
sure you did!
11. Compare the results with the “key” and determine the identity of each
powder.
CLEAN UP: 1. Rinse spot plate with water in the sink. Dry with paper towel.
2. Place all materials in box.
TABLE 1: OBSERVATIONS (In pencil please!)
SUBSTANCE
POWDER
“A”
POWDER
“B”
POWDER
“C”
POWDER
“D”
UNMIXED
MIXED WITH
WATER
MIXED WITH
VINEGAR
MIXED WITH
IODINE
NAME OF
SUBSTANCE
TABLE 2: RESULTS
PROPERTY: SOLUBLE/INSOLUABLE OR REACTIVE
CHANGE: PHYSICAL OR CHEMICAL
SUBSTANCE Letter
A
B
C
SUBSTANCE Name
_______
_______
_______
MIXED
WITH
WATER
PROPERTY
SOLUBLE/INSOLUABLE
OR REACTIVE
CHANGE
PHYSICAL OR
CHEMICAL
MIXED
WITH
VINEGAR
PROPERTY
SOLUBLE/INSOLUABLE
OR REACTIVE
CHANGE
PHYSICAL OR
CHEMICAL
MIXED
WITH
IODINE
PROPERTY
SOLUBLE/INSOLUABLE
OR REACTIVE
CHANGE
Physical or
Chemical
D
_______
SET UP
Powder A
Powder B
Powder C
Powder D
Mystery Powder Key
Substance
Mixed with
Water
Mixed with
Vinegar
Mixed with
Iodine
Baking
Powder
Baking Soda
Cornstarch
Does not
Fizzing
Dissolves in
dissolve in
(reactive)
water (soluble) water- forms a
white mixture
(non-soluble)
Does not
Fizzing
A lot of fizzing dissolve in
(reactive with
(reactive)
vinegar- forms
the water in
a white
vinegar)
mixture (nonsoluble)
Color change to Dissolves in
Color change
greenish/purple iodine but no
to purplish-black and
color change
black
fizzing
(soluble)
(reactive)
(reactive)
Powdered
Sugar
Dissolves in
water (soluble)
Dissolves in
vinegar
(soluble)
Color change to
greenish/purplebrown or yellow
(reactive)
Mystery Powder LAB QUESTIONS
1. All of the unmixed substances (baking powder, baking soda, cornstarch, and sugar)
were white powders. Which powders did you guess correctly from just visual inspection?
2.
Why was it necessary to do additional tests other than visual observation?
In other words, why did knowing the physical and chemical properties of these
substances help you identify them more accurately?
3.
What was the only physical property that you tested? What is the definition of this
physical property?
4. What was the only chemical property you tested? What is the definition of this chemical
property?
5. Describe the difference between a physical change and a chemical change.
6. What clues did you see that indicated a chemical change?
7. What does fizzing indicate the formation of?
8. What does a color change indicate the formation of?
9. Explain why it was important to use a different toothpick stirrer for each well.