Name: _________________________
Date: _________________
Physical and Chemical Changes
Period: ____________
Problem
How do physical changes differ from chemical changes?
Introduction
Matter can undergo physical and chemical changes. Physical changes involve change of one or more physical
properties. Chemical changes involve changes in the composition of the substance.
The following are clues that indicate that a chemical change may have occurred: a color change, the evolution of
bubbles, the formation of a solid (a precipitate), and heat absorbed or produced.
In this lab you will carry out four procedures and make observations. Then you will decide how well the clues enable
you to determine if a chemical reaction occurred. In addition, you will develop molecular definition s of physical and
chemical changes.
Pre-laboratory Assignment
Read the entire experiment before you begin.
Materials
Apparatus
Safety goggles
Lab apron
250 mL beakers (2)
100 mL beaker (2)
Graduated cylinder
Bunsen burner
Striker or matches
Ring stand and wing
Wire gauze
Spatula
Well plates
Beaker tongs
Safety
1.
2.
3.
4.
Reagents
Barium nitrate
Potassium sulfate
HCL (3.0 M)
Magnesium ribbon
Food coloring
Water
The 3.0 M HCl is corrosive. Handle it with extreme care.
If you come in contact with any solution, was the contacted area thoroughly with running water.
You are working with a flame in this lab. Tie back hair and loose clothing.
Safety goggles and lab apron MUST be worn at all times in the laboratory.
Procedure
Part 1
1. Add about 100 mL of water to a 250 mL beaker
2. Add a few drops of food coloring to a beaker (DO NOT STIRR THE BEAKER)
3. Make and record observations for the next 3 minuets.
4. Reserve this solution for part 3
Part 2
1. Dissolve a spatula tip amount of barium nitrate in a small amount of water (about 10 mL) in a 100 mL beaker.
2. Dissolve a spatula tip amount of potassium sulfate in a small amount of water (about 10 mL) in a separate
100 mL beaker.
3. Carefully pore one into another, Make and record observations for the next minuet.
Part 3
1. Arrange the beater from part one and the ring stand as show in the figure below.
2. Light the Bunsen burner and place it under the beaker. Adjust the burner so the hottest part of the flame
touched the bottom of the beaker.
3. Bring the water to a boil. Make and record careful observations.
4. Hold a watch class about 4 inches over the beaker for a couple of minuets as the water boils.
5. Place the watch class on white paper, make and record careful observations.
Part 4
1. Place a FEW drops of 3.0 M HCl in ONE of the well of the well plate.
2. Add a SMALL piece of magnesium ribbon to the acid. Make and record careful observations for the next 2
minuets.
Cleaning up
1. Clean all material (rinse with flowing water)
2. Wash you hands thoroughly
3. Dispose of all chemicals down the drain followed by running water.
4. Return all material to their original locations
5. Have the science teacher verify that your lab station is clean before returning to your seat.
Analysis and Conclusion (to be completed after the lab)
1. For each of the four parts of this experiment, list the clues that a chemical change occurred and tell wither
each change is physical or chemical. Justify each choice.
2. Do any of the procedures give a clue that a chemical change occurred, but are NOT chemical changes?
Which parts of the lab?
3. What was the purpose of the watch glass in part 3? How did it help you to decide if the process was a
physical or chemical change?
4. Make a drawing of each of the four processes (at the atomic level). Discuss how these explain your
observations.
5. Develop your own definitions of chemical change and physical change.
6. Chemists have learned that a chemical change always includes a rearrangement of the ways in which atoms
are grouped. Explain what this statement means and discuss (in paragraph form) whether your observations
in this lab support this statement.