Chemistry I
Instructor: Mrs. Blakely
Laboratory: Physical and Chemical Changes
Background
Matter has properties that help us identify and describe it. Properties can be
considered physical or chemical. Physical properties include things like: color, odor,
density, hardness, solubility, shape, and melting point. They are considered physical
because they can be detected without changing the composition of the material. In a
physical change, no new substance has formed, but the appearance likely has
changed. Chemical properties are determined by a reaction of a substance with
another substance. A new substance with new properties is formed during the
chemical reaction. Evidence that a chemical change occurred can come from: a
temperature change, release of a gas, change in color, production of or change in
odor, formation of a precipitate, and identifying a new substance with new chemical
properties.
A few changes may be difficult to know at first if they are physical or
chemical. The basic test is to ask: what is being altered? If atoms of a substance have
been rearranged and changed, it is a chemical change. If not, it is a physical change.
This lab will allow you to look at changes and classify them as physical or chemical,
based on the observations you make.
Methods- Complete each of the individual tasks, recording results and conclusions
by reaction number.
1. Obtain a square of copper. Hold the copper square on the sides using tongs. Place it in
the inner cone of a nonluminous burner flame for a couple of minutes.
Remove, cool, and observe. Discard in trash.
2. Add 4 drops of food coloring to a 100 ml beaker that has 80 ml of tap water.
Observe. Stir. Observe. Rinse beaker at sink.
3. Measure approximately 5 ml of barium nitrate and 5 ml of sodium sulfate into
separate test tubes. Combine the contents into one tube. Observe. Rinse tubes at
sink.
4. Place a scoopula of sodium bicarbonate into a test tube. Measure approximately 5
ml of acetic acid in a separate test tube. Pour the acetic acid into the sodium
bicarbonate test tube. Observe. Rinse tubes at sink.
5. Obtain an ice cube and place on a watch glass. Observe initially and observe again
in several minutes. Discard any remains in sink.
6. Obtain 5 ml of cupric sulfate solution and add to a test tube. Add a few pieces of
mossy zinc. Allow five minutes for the reaction to occur. Observe. Discard any liquid
in the sink and solid in the trash.
7. Observe the solid sulfur and iron samples provided. Obtain a tube containing a
S/Fe mixture. Move a magnet around the bottom and sides of the tube and observe.
Return the tube to same location.
8. Place a scoopula of sugar in an aluminum dish. Flip the burner flame (no cone, Al
melts at 660oC) to heat the sugar for about a minute. Observe. Allow to cool, and
then discard in trash.
9. UNDER THE FUME HOOD, take a small copper sample and place it in a 30 ml
beaker. Add about 10 ml of nitric acid (conc). Allow the change to take place. When
complete, add water from the wash bottle until a change is evident. Note changes.
Rinse beaker once the reaction is over.
Station #
1. Heating of
Copper(Cu)
2. Food Coloring &
Water
3.
BaNO3 & NaSO4
4. Sodium
bicarbonate &
Acetic acid
Observations
Physical/Chemical Change
5. Ice
6. 6. CuSO4 & Mossy
Zinc
7. Sulfur & Iron
8. Heating of Sugar
9. Copper & Nitric
acid (HNO3)
Questions
1. Provide an example of how metal could be physically changed?
2. What classification of matter is the initial copper sample in steps 1 and 9?
3. What is a precipitate?
4. What are the common names for the two substances used in method #4?
5. Why was method #9 done under the fume hood?