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Lab # 3: Chemical or Physical Changes Lab
Chemistry 1
Problem
What is the difference between a physical change and a chemical change? How can you tell when
a chemical change has taken place?
Introduction
Matter is described by scientists using physical properties such as color, odor, state,
melting point, boiling point, and solubility. Water can be described as a clear, odorless liquid at
room temperature.
Matter can undergo two different types of changes – a chemical change or a physical
change. A physical change is one in which only a physical property of the substance changes.
For example, an ice cube melts (or changes state from a solid to a liquid); but, before and after the
change, the substance is still water. A chemical change is one in which the chemical composition
(or the atoms that make up the substance) change. For example, when sugar (C6H12O6) is heated
in a flame, it decomposes (or breaks down) into carbon (C) and water (H2O).
C6H12O6(s) + heat  6 C(s) + 6H2O (l)
You can see that the arrangement of carbon, hydrogen, and oxygen atoms that make up the sugar
is no longer the same way after the change.
The following are clues that a chemical change may have occurred: a color change, the evolution
of bubbles, the formation of a solid, and a change in the heat of the solution.
In this lab, you will visit 6 different lab stations located throughout the classroom. At each
station, you will work with a partner to complete the procedure for that station as it is written below.
Closely observe what happens to the starting materials. Talk with your partner and decide whether
you think a chemical change or a physical change occurred; write “chemical change” or “physical
change” on the designated line. Then, in full sentences, explain why you think a chemical change
or physical change occurred. Use your observations as evidence to support your claim.
Materials
1. Goggles
2. Apron
3. Well plate (1 per team)
4. Station labels
5. NaI (1 M)
6. AgNO3 (1 M)
7. Luminol Solution (E)
8. Bleach Solution (F)
9. H2O2 (10% solution)
10. “Blood” solution
11. Dry ice (1 piece per team)
12. CuNO3
13. “Unknown” white solid
14. Melting Point Block with hot plate & thermometer
15. CuSO4 hydrate
16. Crucible and Hot plate
Pre-lab Assignment
Read the experimental procedures before you begin.
Answer the following questions:
1. What is the difference between a chemical change and a physical change?
2. What is one example of evidence that a chemical change has occurred?
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Procedure
1. Find an available station to begin the lab. You do not have to complete the stations in order
from 1 to 7. You can start at any station. However, once you chose a station, continue through
the rotation in order. For example, if you start at station 3, you will proceed to 4, then 5, etc.
You will then rotate to 1, proceed 2, then 3, etc.
2. Follow the directions as written for each station. Observe and decide if a chemical or physical
change is taking place. Complete the appropriate box. Use your observations to support your
claim.
3. Restore the station to its original condition before you move on.
Station 1
Directions: Add 10 drops of NaI solution to a well. Add 2 drops of AgNO3 to the same well.
Was this a physical or chemical change? __________________________
Why?
Station 2
Directions: Fill a well ½ full with hydrogen peroxide. Add 2 drops of “blood” to the same well.
Was this a physical or chemical change? __________________________
Why?
Station 3
Directions: Place a small piece of dry ice into a well and observe for a few minutes.
Was this a physical or chemical change? __________________________
Why?
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Station 4
Directions: Fill a well ½ full with water. Add a small amount of copper nitrate (CuNO3) to the same
well and stir.
Was this a physical or chemical change? __________________________
Why?
Station 5
Directions: Be sure to place your well plate on a clean, white sheet of paper. Add 10 drops of
Solution E (Luminol) to a clean well of your well plate. Add 10 drops of Solution F (bleach) to the
same well and observe.
Was this a physical or chemical change? __________________________
Why?
Station 6
Directions: Use forceps to place a blue crystal of copper (II) sulfate hydrate into the mortar. Use the pestle to
grind the blue crystal.
Record your observations.
Was this a physical or chemical change? __________________________
Why?
Use a spatula to scrape the powder into a crucible to use for Station 7.
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Station 7
Directions: Turn on the hot plate to a setting of "high." Measure and record the mass of the crucible and
blue powder from Station 6: _________________
Spread the blue powder evenly over the entire crucible bottom, all the way to the outside edge. Using
crucible tongs (see picture), place the crucible on the hot plate and heat for 3 minutes.
Use tongs to remove the crucible from the hot plate and allow it to cool until you can comfortably pick it up.
Measure and record the mass of the crucible and its contents: _______________
Record your data and observations.
Was this a physical or chemical change? __________________________
Why?
Put the powder in the trash.
Wipe out the crucible with a dry paper towel and reset the station.
Station 8 – Using Physical Properties to Identify an Unknown Solid
Directions: Use the physical properties of state, color, odor, solubility, and melting point to identify
an unknown solid. Add 2 mL of water to a test tube. Add a match-head sized sample of the
unknown to the test tube. Use the MSDS sheets to look up the physical properties of known
substances and compare these properties to your observations to make your identification.
Observations:
Color:
Odor:
Soluble?:
Melting Point:
Identification:
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Analysis and Conclusions
1. Sometimes a physical change produces the same clues as those normally associated with a
chemical change. Did this happen in any of your procedures; if so, which ones? Describe at
least two examples.
2. Draw a picture of what happened, at the molecular level, when copper nitrate was added to
water at Station 4. You may use shapes to symbolize the substances.
3. At Station 7, what happened to the mass of the copper (II) sulfate hydrate after it was heated?
Explain why you think this was observed.
4. Draw a picture of what happened, at the molecular level, to the piece of dry ice as it lye on the
lab bench at Station 3.
5. What evidences of chemical changes did you observe in this lab? List them all.
6. Explain how you used physical properties to identify the substance at Station 8. Were certain
physical properties more helpful than others? Explain why.
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