How To Write A Lab Report Chemical Change

Dagondon, Vanessa Olga Date of experiment: July 1, 2013
Nablo, Janica Mae Date of submission: July 18, 2013
Palmitos, Isabel

Experiment # 2 chemical changes

I. INTRODUCTION
Chemical changes occur when a substance combines with another to form a new substance whether by combination reaction, combustion reaction, decomposition reaction and etc. These changes can be observed by evolutions of gas, appearance or disappearance of a precipitate, evolution or absorption of heat or even change in color.
This experiment aims to observe the different chemical changes copper undergoes in different conditions.

II. METHODOLOGY

1. Precipitation of Copper (II) Hydroxide

Materials used: 0.100 M Cu(NO3)2 solution, 250-mL beaker, 6.00
About 1.5 g zinc dust was slowly added to the solution in the previous activity with constant stirring. The chemical changes were observed and noted. It stirred until no reaction is occurring and then more zinc was added to make the solution color less. The completeness of the reaction was tested by adding a few drops of the solution in a test tube containing 1 mL of 6.00 M NH3.This solution was compared to the controlled solution(prepared by adding a drop of 0.100 M Cu(NO3)2 solution and 2 drops of NH3 to 1 mL water). Observations were noted. The supernate in the latter step was decanted and discarded and the precipitate was washed in the beaker twice using 10 mL water. The wash water was decanted and discarded after each washing. A 10 mL water and a 2 mL 6.00 M HCl were added to the precipitate slowly. It was stirred until no more change is observed. The precipitate was settled and the supernate was again decanted and discarded. The precipitate was washed again with 10 ml of water. The wash water was again decanted and discarded. The entire solid (precipitate) was transferred to a beaker to a weighed filter paper. The filter paper was folded and was kept in the locker to be observed in the next
The supernate was then filtered through the use of filter paper into the Erlenmeyer flask. The filter paper having the copper (II) oxide solid used was washed with 6.00M H2SO4 thus having a reaction of:
CuO(s) + H2SO4(aq) CuSO4(aq) + H2O(l)
It was noted that from the colorless or clear filtrate, it changed into blue. Also, there was a formation of blue precipitate when 6.00M H2SO4 was added.
The CuSO4 solution obtained was then added with zinc dust having a chemical equation as follows:
CuSO4(aq) + Zn(s) ZnSO4(aq) + Cu(s)
During the addition of more zinc dust, it was observed that there were bubbles. HCl was added to the solution to dissolve the remaining zinc. The precipitate was then after allowed to settle and the supernate was discarded. The remaining solid was transferred into a filter paper. The filter paper was then air dried and was weighed after. The recorded mass of the filter paper and the solid was 1.32g. It was also observed that the color of the solid after air drying was metallic brown.
The obtained solid was then placed in an evaporating dish and was heated over a Bunsen burner. The reaction can be described as follows:
2Cu(s) + O2 (g) 2CuO (s)
The metallic copper solid changed into black copper (II) oxide after the heating