Introduction to Chemical Laboratory

This lab was designed to teach us how to work well in the lab and to make all kinds of observations, specifically quantitative and qualitative observations. In class, we have been going over appropriate lab behavior, as well as taking notes and quizzing on chemical and physical attributes, etc. Our hypothesis was that when each item was added to the mixture, chemical changes would take place.
The materials used in this lab were as follows:

• beaker
• copper(II) sulfate pentahydrate
• graduated cylinder
• stirring rod
• thermometer
• small square of aluminum foil

Procedure:

1. We got in a group of two and retrieved all the appropriate safety equipment; then, we set up our lab station.
2. To set up our lab station, we acquired all of the above listed materials. Taking the beaker, we then filled it with approximately 90 ml of water. We then took the following observations: the beaker was 2/3 full; there were 88 ml of water; the temperature was 22.5 degrees Celsius; the water was, of course, clear.
3. At that point, we made the quantitative observations that there were approximately eighty-eight milliliters of water, and in the beaker, the water filled it to the 2/3 point. The qualitative observations we made were that the water was clear, as well as the fact that the temperature was 22.5 degrees Celsius.
4. The next step we took was to use the scoopula to add an inexact amount of copper(II) sulfate pentahydrate (about 1/4 of the scoopula) and to mix it in the water until it was completely dissolved. The mixture was homogeneous because the copper(II) sulfate pentahydrate was dissolved and we were unable to see any difference in the particles. The temperature was 22.2 degrees Celsius.
5. Then we crumpled the aluminum into a loose ball and added it to the solution; we then stirred gently for about 15 seconds.  We made the following observations: the color stayed blue, the mixture is now heterogeneous because of the foil, the volume is increased.  To our knowledge, there was no chemical change.
6. Cleaning the scoopula came next, after which we added a large scoop of NaCl to the beaker. We stirred until all of the sodium chloride was dissolved and began to make observations, which are as follows: the color had become greenish and was fading, foil appeared to be falling apart and turning, the mixture continued to change color, there was a slight bubbling in the mixture, the temperature was 24.0 degrees Celsius, the volume had increased from the beginning eighty-eight milliliters. The change we saw was clearly chemical because of the temperature change and bubbling without heat, the color change of the foil and the solution, and the change in the foils shape and mass as it disintegrated. We observed that there were three states of matter present, and the precipitate was probably copper.
7. Our final step was to follow the proper clean-up procedures, such as emptying the beaker correctly and cleaning our lab station well, and then returning to our desks to await further instruction. We discussed briefly the lab in class.

Our hypothesis was partially correct. While there were several chemical reactions, some of the steps only involved physical changes. For example, when we added the aluminum foil to the original solution, we did not observe a chemical reaction. On the other hand, when the NaCl was added, there were clearly chemical changes taking place. One question we had at the end of the lab was how high would the temperature rise before another noticeable change?