Observing Chemical Reactions                  Name ___________________________________

Objectives:

1. To make as many observations as possible of a chemical reaction.

2. To learn to distinguish between observations and interpretations.

3. To learn to distinguish between qualitative and quantitative observations.

Equipment:

1 100 mL beaker                      1 thermometer                          1 glass‑stirring rod

1 plastic spoon                         1 magnifying glass                                 safety goggles

 

Materials :

Copper (II) chloride dihydrate CuCl2·2H2O                  aluminum foil, 8cm x 8cm

 

Procedure:

As you perform the experiment, record your observations in the table.

1. Obtain a sample of copper (II) chloride dihydrate, CuCl2·2H2O. Describe the crystals in as much detail as you can, and make as many observations as possible.

2. Fill the 100 mL beaker about one‑fourth full of tap water. Without stirring, add one level teaspoonful of crystals to the water. Record your observations of the mixture. Observe both the crystals and the water.

3. Stir the mixture with the glass rod until the crystals are completely dissolved. Record your observations of the solution.

4. Place a thermometer in the copper (II) chloride solution and note the temperature. Then, loosely crumple the aluminum foil into a ball. Place the ball of aluminum in the solution and record your observations of the mixture.

 

Caution: Observe the mixture from the side, do not look directly down into the beaker.

 

Continue to observe the mixture for at least 10 minutes and note any change in temperature. Does stirring the mixture have any effect on the reaction?

5. When the reaction is complete, pour off the liquid portion of the mixture into the sink. Discard the solid contents of the beaker into the chemical waste container provided by your teacher. Wash and dry the equipment that you used. Wash your hands thoroughly.

System

Observations

Dry copper (II) chloride dihydrate

 

Copper (II) chloride in water

 

Stirred Copper (II) chloride in water

 

Copper (II) chloride plus aluminum foil

 

Initial Temperature

 

Final Temperature

 

Materials:
            baking soda      calcium chloride           phenol red solution        self-locking plastic bag.

Procedure

  1. Put 1 teaspoon of baking soda (NaHCO3) into the self-locking plastic bag. CAUTION: Wear a laboratory apron, and goggles when using these chemicals.
  2. Put 1 teaspoon of calcium chloride (CaCl2) into the bag with the baking soda and mix the two substances.
  3. Shake all the powder into one corner of the bag, and twist to seal it.
  4. Put 10 ml of the phenol red solution in graduated cylinder
  5. Pour the phenol red solution into the plastic bag, keeping the powder dry.
  6. Carefully seal the self-locking plastic bag, removing as much air as possible.
  7. Untwist the bag and allow the powder and liquid to mix. Be careful not to unseal the bag.
  8.  Hold the bag in your hands and observe any changes. CAUTION: Wash your hands after the activity.
  9. Pour the mixture down the drain and rinse sink with plenty of water.

Data Record

Data Table: Observations

 

Properties

 

Before Mixing

After Mixing

Baking soda

 

 

Calcium chloride

 

Phenol red

 

 

Conclusion:

  1. What is a chemical change?

 

 

 

 

 

  1. What indications did you see that chemical changes happened in today's labs. List at least 6.