Chemistry Lab # 1: Physical and Chemical Changes
Introduction: During this lab you will observe some chemical and some physical changes in matter. During a
physical change the composition of the substance does not change and they are easily reversed. Melting and
dissolving is a couple of examples of physical changes. Chemical changes result in new substances being
formed, substances with new compositions. Signs of a chemical reaction include one or more of the following:
energy (heat) released or absorbed, precipitate forming, gas bubbles, permanent color change.
Purpose: To observe chemical reactions and identify them as physical or chemical changes.
Apparatus:
- 150 mL test tubes and stopper
- 10 ml graduated cylinder
- pippette
-150 mL beakers
Materials
- copper (II) sulfate pentahydrate
-sodium thiosulfate solution (0.5 mol/L)
-potassium chloride
- distilled water
- sodium hydroxide
-zinc oxide
-lead nitrate
-copper(II) chloride
-magnesium ribbon
- matches
-Bunsen burner
-tongs
-scoopulas
-safety goggles
-hydrochloric acid (2 mol/L)
-potassium iodide
-aluminum foil
-phenolphthalein
CAUTION:
The hydrochloric acid is a corrosive substance. It can cause damage to skin and clothing. Wash
away and spills of hydrochloric acid with plenty of water. Lead nitrate is a poisonous substance. Avoid contact
with both solid lead nitrate and with solutions of lead nitrate.
Procedure: All of the materials you require to complete each step are on the tray at each lab station. Each
tray is clearly marked 1 through 8 and each beaker has a label identifying the chemical. Read the instructions
for each station carefully before you begin. Record your observations for each step of the experiment in the
correct row of your data table. Remember, if you start at station 5 you must record your observations in the
row for station 5. (if nothing happens immediately wait a while and observe again).
A. Station 1: Place 1 ml (fill pipette) of 1.0 M sodium hydroxide (NaOH) in a test tube. Add 3 ml of tap
water using a graduated cylinder. Add 3 drops of phenolphthalein. Cover the tube with a rubber
stopper and shake it gently. Observe. Add 1.0 M hydrochloric acid (HCl) one drop at a time until a
colour change has been observed. Record all observations in the data table. Clean the test tube and
place it in the test tube rack.
B. Station 2: Place about 0.5 g (cover the tip of the scoopula) of copper(II) chloride (CuCl2) in a test tube
and add 5mL of water using a graduated cylinder. Carefully swirl to dissolve the copper(II) chloride.
Add a small piece of crumbled aluminum foil to this solution. Don’t forget to feel the test tube! Wait 2
minutes and record your observations. Clean the test tube and place it in the test tube rack.
C. Station 3: Place a few crystals of lead nitrate (PbNO3) in a test tube, add 5 ml of water using a
graduated cylinder and then agitate (swirl) to dissolve the solid. Observe and record all observations in
the data table. DO NOT THROW THIS SOLUTION AWAY YET! Take this test tube to station #4 with you.
D. Station 4: Add 0.5 g (cover tip of scoopula) of potassium iodide (KI) to a new, clean test tube. Add 5
ml of water using a graduated cylinder. Carefully swirl to dissolve the potassium iodide. Observe and
record all observations in the data table. DO NOT THROW THIS SOLUTION AWAY YET! Take this test
tube, along with the one from station #3, to station #5.
E. Station #5: Add the solution from part C to the solution from part D. Observe and record all
observations in the data table. Clean all test tubes and place them in the test tube rack.
F. Station #6: Place 1 ml (fill pipette) of hydrochloric acid (HCl) in a test tube and then add 1 ml (fill
pipette) of sodium thiosulfate solution (Na2S2O3). Gently swirl the test tube to mix the two solutions.
Observe and record all observations in the data table. Clean the test tube and place it in the test tube
rack.
G. Station #7: Place about 0.25 g (cover the tip of the scoopula) of zinc oxide (ZnO) in a test tube. Hold
the bottom of the test tube in the flame of the Bunsen burner and heat until you observe a change.
Remove the test tube from the flame, place it in the rack, wait 30 seconds and record your
observations in the data table. Allow it to cool for a few minutes and clean the test tube.
H. Station #8: TEACHER DEMO: Take a small piece of magnesium ribbon (3 cm long) and hold it in a pair
of tongs. Hold the magnesium ribbon in the Bunsen burner flame. Do not look directly at the ribbon
as it may damage your eyes. Record all observations.
I.
TEACHER DEMO: Add 0.5g of barium hydroxide to a test tube. Then add 0.5g of ammonium
thyocyanate to the same test tube. Cork the test tube and shake well until you observe a change.
Record observations in the data table.
Observations: Complete the chart given to you by your teacher and answer the following questions:
Analysis questions:
1) Is the dissolving of table salt in water an example of a chemical or physical change? What
experimental procedure would support your answer?
2) You heat a piece of platinum wire in a burner flame, the wire glows red. What experimental procedure
could you perform to find if this is an example of a chemical or physical change?
3) Does a change in color always indicate a chemical change? Use your experimental evidence to support
your answer.
4) Give an example of a physical change which creates bubbles.
5) Is one clue off of the list enough to determine that a chemical change has occurred? Explain why or
why not.
NOTE: Each student must have a rough copy of the lab in their lab folder
The good copy of your lab MUST include:
1) A title
2) A purpose: Copied directly from lab sheet
3) Materials: Copy directly from lab sheet
4) Procedure: The procedure was followed as stated on the lab sheet.
4) Observations: Please make a good copy of the observations table.
5) Analysis questions: Please answer in full sentences.
6) Conclusion: Answer the question from the purpose. Here you will sum up what you learned and show
me you understood the purpose of the lab.
Observations:
Station Observations (bubble, colour change, heat etc…)
1
2
3
4
5
6
7
8
Chemical or physical change?
Station Observations (bubble, colour change, heat etc…)
Chemical or physical change?
1
Initial color change, clear to pink
Color reversed back to clear
Physical Change
2
Heat and bubbles produced
New substance forming on foil
Chemical Change
3
Lead nitrate dissolved in the water
Physical Change
4
Sodium iodide dissolved in the water
Physical Change
5
Precipitate formed when two solutions were mixed
Turned a bright yellow color
Chemical Change
6
Color change (milky white or opaque)
Foul smell
Chemical Change
7
Zinc oxide turned yellow when heated
Turned back to white when cooled
Physical Change
8
Magnesium ribbon burned with a bright white flame
Reduced to ashes
Chemical Change
1. Dissolving salt would be a physical change. The water could be boiled, it would evaporate and the salt
would be left behind.
2. Allow the platinum wire to cool; if it stays red it is a chemical change, if it goes returns to the normal
color it is a physical change.
3. No, a change of color is not always an indicator of a chemical change. In the first station we saw a
color change that was reversed.
4. A physical change that creates bubbles would be boiling water to produce water vapour.
5. No, it is not always enough but in some instances you can tell right away (i.e., burning)