Lab Activity 4: Observation - An Important Scientific Tool 

 

Purpose &  Some Background:

            Chemists are always using their senses (except taste) to detect change or activity in an experiment. They then question how or why something occurred and try to guess at a logical explanation. An educated guess is called a hypothesis. These scientists will next set up an experiment to either prove or disprove their hypothesis. Depending on the results, the hypothesis is proven correct, shown to need revisions, or discarded entirely. These are all steps in the scientific method.
You will now have the opportunity to try your hand (and mind) at the scientific method. Remember to think logically. Your recorded observations must make sense. Don't count any observations out, record it down. Try to use all your senses (except taste) to help yourself evaluate what you observe. Produce a formal lab report and it will be collected the following lab.

Teacher’s Note:

 By the end of this lab, I want you to:

1.      Understand the importance of making observations.

2.      I want you to add procedures to your lab in order to determine the mass and number of moles of cooper (II) chloride and aluminum foil.

Materials:

           

-1 clean, dry, 100 ml beaker -Plastic Spoon
-1 clean dry, 250 ml beaker -Copper (II) chloride
-Water -Forceps
-Stirring rod -Aluminum foil (½ cm x 6 cm strip)

Procedures:
1. Place a level spoonful of the copper (II) chloride in the small beaker.
2. Fill the 250 ml beaker about half full of water. Touch the beaker and record the warmth.
3. Slowly add the copper (II) chloride to the water. DO NOT STIR! After a few minutes record the color you observe near the crystals in the water.
4. Now stir the solution with a stirring rod until the crystals disappear. Record the color of the liquid.
5. Touch the beaker and record the warmth compared to step 2.
6. Loosely coil the aluminum strip around a pencil or test tube to coil the foil. Remove the foil from the pencil or test tube and using forceps, drop the aluminum coil in the copper (II) chloride solution.
7. After about 5 minutes, touch the beaker again and record the warmth. Continue observing the solution for another 5 to 7 minutes.
8. Record all changes that you observed during the 10 to 12 minutes after the aluminum was added. There are at least eight changes.

Interpretations that must be included in your lab:

1. What questions do you have concerning what you observed after adding the aluminum?

2. What guesses (hypotheses) might be given as possible answers to these questions?

3. What were your results for the mole and mass determination?