Evidence of Chemical Reactions Lab

Data Processing

        Balanced Equations:

Test 1:                                                                This is a double displacement reaction.

Test 2:                                                                   This is a double displacement reaction.

Test 3:                                                                This is a double displacement reaction.

Test 4:                                                                This is a single replacement reaction.

Test 5:                                                                           This is a double displacement

reaction.

Example writing of Equation:

Reactants: HCl and NaOH dissolved in water, thus the left side is

The Hydrogen and Sodium metal will swap, in a double displacement format, hence the right side will be                         which can be rewritten as                         and since NaCl is soluble the complete right side will be                                  thus the entire equation is:

Data Presentation

        

† Only measured for Test 1                                ‡ Small amounts of gas may not have been noticed

Concluding

        The purpose of this lab is to investigate some of the kinds of evidence that are seen for chemicals changes and reactions.

        In accordance with the evidence presented above, it can be seen that some of the most common types of evidence are:

• Heat – Test 1, for example, had no visible reaction but its temperature instantly rose 3ºC as a result of the energy released from the reaction of the acid (HCl) and base (NaOH).
• Bubbles – Test 2 bubbled vigorously, showing that a gas was formed as the HCl reacted with the CaCO3.
• Noise – the reaction in Test 2 was so intense that it made a fizzing sound.
• Precipitate – solid particles (AgCl, Cu(OH)2) are often found floating or sunken in the liquid, a product of the reaction.
• Colour Change – in Test 4, the liquid was initially a very bright, pure blue but as time progressed it became a deep, rich turquoise
•         Consistency Change – Test 5 began with two watery liquids, but when they were combined there was a strong increase in viscosity. Also, the (metal) silver nitrate in Test 3 reacted instantly to form a substance that resembled tissue paper that was soaked in water.

Evaluation of Procedure

         This lab was, altogether, an excellent simple procedure for learning about different types of reactive evidence. Be that as it may, there is still room for improvement.

        The first aspect of the procedure that is not good enough is the detail of the data. There is only one instance of quantitative data – the temperature values in Test 1 – the rest is simply description. It would be good to do other sorts of measurements, as these make for better comparison and presentation, and are much more useful in the real world, beyond high school chemistry.

        Another similar issue is that there is only a single trial done for each experiment. Were this to be done more precisely, it would of course require the use of measurements like mentioned above.

        However, many of these suggestions are not actually necessary for the simple purpose of the lab, which can still be achieved with extremely limited accuracy, precision and detail.  Complicating the lab further would add a significant amount of time and energy to the procedure and write-up, and would actually not yield further conclusion. When considering the purpose, precision and detail are irrelevant.

        In all reality, this lab was no more complicated than it needed to be, but not too simple either. It actually needs very little in the way of improvement. A few more tests could have been added, such as another one that included a temperature change and another with noise, but also to show types of evidence that were not covered herein, such as the spark and flame that are exhibited by the reactions of alkali metals with water.

Improving the Investigation

        Doing other sorts of measurements – viscosity, mass of precipitate formed relative to amount of reactants, opacity – would allow for greater comparison and presentation, but would not actually be necessary. Using more precise tools and doing more trials would have the same effect, but none of these actually produce more examples of types of reactions, which is the purpose of the lab.

This lab could, however, be improved by performing a few more experiments, to include more evidence, such as spark and flame.