Introduction:
We tend to think of ourselves as
good observers. Yet there is much more to observation than meets the eye. It takes concentration, alertness to detail,
ingenuity and patience. It also takes
practice. Substances are characterized by their individual and sometimes unique
properties. The color, melting point, boiling point, and density of a substance
are examples of its physical properties. A physical
property can be measured and observed with out changing the composition or
identity of a substance. On the other hand, "hydrogen gas burns in oxygen
gas to form water" describes a chemical property of hydrogen. Chemical properties can be measured and observed
when the composition changes.
Objective:
To be able to
distinguish physical and chemical changes, and to describe characteristics of
each
Materials:
Candles,
matches, chalk, vinegar, soluble starch, water, iodine solution, phenolthalein
solution, Alka-Seltzer, milk of magnesia, ammonia solution, iron (III)
chloride, hydrochloric acid, magnesium ribbon, spot plates, pipettes, mortar
and pestle, and test tubes
Procedure:
1.
Create
a data table on a separate piece of paper, (or page three of your report) based on the steps involved in this
experiment. Place a candle in a drip
tray, light a match and ignite the candle. Observe for several seconds and then
extinguish the candle.
2.
Grind
a 3 cm piece of chalk in a mortar and pestle. Place some of the ground chalk in
a spot plate, add three drops of vinegar. Observe for several second and then
clean up the mortar and pestle and spot plate.
3.
Add
0.5 grams of soluble starch to a small beaker and then add approximately 100 ml
of tap water. Add 3 drops of iodine solution to the starch solution. Observe
for several second and then clean out the beaker.
4.
Place
approximately 200 ml of tap water in a medium size beaker and add a single
Alka-Seltzer tablet. Observe for 30l second and then clean out the beaker.
5.
Place
5 drops of milk of magnesia in a spot plate using a pipette and then add 3
drops of phenolthalein. Observe for several second and then clean out the spot
plate.
6.
In a
test tube place 5 drops of ammonia and then add 5 drops of iron (III) chloride.
Observe for several second and then clean out the test tube.
7.
Using
a pipette, place 7-8 drops of hydrochloric acid in a test tube. Place 3 pieces
of magnesium ribbon, approximately 1-2 mm in length each, into the test tube.
Observe for several second and then clean out the test tube.
Data Table:
Constructed
based on the procedure and allows enough space for appropriate answers. In this
experiment, there should be three columns titling; procedure, observations,
and type of change.
Analysis:
1.
Group
all the procedures that were chemical changes. Describe the common theme
between these reactions.
2.
Group
all the procedures that were physical changes. Describe the common theme
between these reactions.
Questions:
1.
What
is the definition of a physical change?
2.
What
is the definition of a chemical change?
3.
What
are the four evidences of a chemical change?
4.
List
at least 2 other types of physical changes that did not occur during lab.
5.
Which
procedures had both physical and chemical changes taking place?
Conclusion:
In
your conclusion, make specific references to objective(s) and results. The conclusion should also include sources of
experimental error and suggestions for improvement that are thoughtful and well
written. Be concise!