Physical and Chemical Properties and 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. Remember a
physical change involves a change in a physical property but the substance
does not change its identity. When a chemical change occurs a new
substance is produced. There are hints like a color change or fizzing (a gas)
that indicate a chemical change has taken place because a new substance is
produced.
PART 1
Objective: To observe the physical properties of unknown white solids with as
much detail to distinguish between them.
Materials:
-
4 watchglasses
4 unknown white solids
Procedure:
Describe each of the unknown solids A, B, C, and D using the Data Table
for Part 1
PART 2
Objective: To determine the identity of four mystery powders which are similar in
appearance by observing a physical property (solubility) and a chemical property
(reactivity). You will also determine whether mixing these “mystery powders” with
water, vinegar or iodine causes a physical or chemical change.
Materials:
-
Well tray
Beaker of water with dropper
Iodine dropper-bottle
Flask of vinegar with dropper
4 unknown powders marked ‘A’, ‘B’, ‘C’, and ‘D’.
4 spatulas to go with each powder…DO NOT MIX!
toothpicks
Procedure:
(Before starting get a good size piece of paper towel to use to clean the
spatula in between stirring)
1. Using the spatula for “A” scoop up a very small amount of Powder
“A” and place it in well #1. The powder should just cover the bottom.
2. Place the same amount of Powder “A” in well #5 and well #9.
3. Use spatula for “B” and place the same amount of Powder “B” in well
# 2, 6, and 10.
4. Use the spatula for “C” and place the same amount of Powder “C” in
wells # 3,7,and 11.
5. Use the spatula for “D”. Place Powder “D” in wells # 4,8,and 12.
6. Use the eyedropper to place water into the well #1 so that it fills
most of the well. Use a clean toothpick to stir the mixture. RECORD
YOUR OBSERVATIONS IN THE DATA TABLE.
***DO NOT USE THE SPATULA TO STIR, DO NOT USE IT FOR
ANYTHING OTHER THAN TO SCOOP.
7. Use the dropper next to the vinegar bottle to add 10 drops of vinegar
to the powder in well # 5. Stir with a clean toothpick and record
observations.
8. Use iodine dropper-bottle to add 10 drops of iodine to well #9. BE
CAREFUL BECAUSE IODINE WILL STAIN. Stir with a clean
toothpick. Record observations and WIPE THE SPATUALA CLEAN
WITH A PAPER TOWEL.
9. Repeat the same process with the Powder “B” (#2,6,10), Powder “C”
(#3,7,11) and the Powder “D”(#4,8,12)
10. Always use a clean toothpick to stir.
11. RECORD ALL OBSERVATIONS.
CLEAN UP: 1. Rinse spot plate with water in the sink. Dry with paper towel.
2. Place all materials in box.
Well-Tray Set Up
Powder A
Powder B
Powder C
Powder D
Part 3:
Objective: When solutions of metals are heated in a Bunsen burner flame, they
give off characteristic colours. For example, sodium makes the flame turn bright
orange – this is the same orange colour made by sodium street lamps and many
fireworks. You can be an analytical chemist or forensic scientist in this activity, by
finding out what colour flames different metals make, and working out the identity
of some unknown metal solutions
Pre-lab:
Write down the known colors for the given elements:
1. Sodium
2. Potassium
3. Copper II
4. Copper III
5. Strontium
6. Calcium
Materials:
- Chrome wire (7)
- 7 unknown solutions
- Bunsen burner
**Observe teacher perform the magnesium strip test
CREATE YOUR OWN RESULTS TABLE
Procedure:
- Dip the tip of the chrome wire into the solution
- Hold over the middle of the flame and observe color change
- Hold in flame until the color is regular orange color
- Do not mix the chrome wires
RESULTS
Part 1:
SUBSTANCE
“A”
“B”
“C”
“D”
Color
Crystal/powder/rock
Shiny or Dull
Fine or coarse
NAME OF
SUBSTANCE
Part 2:
TABLE 1: Physical or Chemical Changes of Unknown White Solids
SUBSTANCE
POWDER
POWDER
POWDER
POWDER
“A”
“B”
“C”
“D”
White
White
White
White
UNMIXED
Crystals
Powder
Powder
Powder
MIXED WITH
WATER
MIXED WITH
VINEGAR
MIXED WITH
IODINE
NAME OF
SUBSTANCE
TABLE 2:
PROPERTY: SOLUBLE OR REACTIVE CHANGE:PHYSICAL OR CHEMICAL
SUBSTANCE
MIXED
WITH
PROPERTY
WATER
CHANGE
MIXED
WITH
PROPERTY
VINEGAR
CHANGE
MIXED
WITH
IODINE
PROPERTY
CHANGE
Part 3:
SUBSTANCE
COLOR
NAME OF
UNKNOWNS
A
B
C
D
E
DISCUSSION
PART 1
1. Research the physical characteristics of solid form of the following:
a. Sodium chloride
b. Sodium bicarbonate
c. Calcium biphosphate
d. Sodium acetate
2. Identify your unknown solids based on your physical observations (this
would be discussion section).
PART 2
1. How were all of the unmixed substances (sodium chloride, baking soda,
cornstarch, and sugar) similar to each other in terms of their physical
properties?
2. What was the only physical property that you tested? What is the
definition of this physical property?
3. What was the only chemical property you tested? What is the definition
of this chemical property?
4. Describe the difference between a physical change and a chemical
change.
5. What clues did you see that indicated a chemical change?
6. What does fizzing indicate the formation of?
7. What does a color change indicate the formation of?
8. Explain how you were able to identify the mystery powders.
9. Explain why it was important to clean the metal spatula after you stirred
each powder in a liquid.
STEP FURTHER (OPTIONAL, BUT NECESSARY FOR AN A+) FROM PART 2
Find the chemical formula for Sodium chloride, Baking Powder, Cornstarch and
Sugar (glucose). List the names of the elements that are found in each.
Find the chemical formula for water, vinegar, and iodine. List the elements that
are found in each.
Which mystery powder is a combination of two of the other powders? Name the
two powders that make it up and explain why you think this is true.
Part 3
Mystery Powder Data
Substance
Unmixed
Sodium
Chloride
Fine white
crystals
Baking Soda
Cornstarch
Fine white
powder
Fine white
powder
Mixed with
water
Dissolves in
water
(soluble)
Dissolves in
water
(soluble)
Does not
dissolve in
water-forms a
white mixture
(non-soluble)
Mixed with
vinegar
Dissolves in
vinegar
(soluble)
A lot of fizzing
(reactive)
Mixed with
iodine
Dissolves
Dissolves in
iodine
(soluble)
Color change
Does not
to purplishdissolve in
black
vinegar- forms (reactive)
a white
mixture (nonsoluble)
Powdered
Sugar
Fine white
powder
Dissolves in
water
(soluble)
Dissolves in
vinegar
(soluble)
Color change
to greenishbrown or
yellow
(reactive)