11th Practical Lesson: 1P12 Forming Compounds

We had this practical lesson on the same day as 1P11 but I did not have space to put it in my previous post. We had to cram two practicals in the same day and it was quite a mad rush. As usual, we had to gather our materials first:

1. Magnesium ribbon
2. Iron fillings
3. Dilute sulfuric acid
4. Lead (II) nitrate solution
5. Sodium chloride

Our apparatus include: test tubes, Bunsen burner, evaporating dish, test tube holder and a pair of tongs. There were some things that were aimed to achieve at the end of the practical and we had to take note of them. It was to investigate the formation of these compounds by:

1. Reacting two elements
2. Reacting an element and a compound
3. Reacting two compound

With these aims clear in our minds, we started our experiment. Our first experiment was to hold a magnesium ribbon with a pair of tongs, place it in the Bunsen flame and when the magnesium ribbon catches fire, hold the pair of tongs above the evaporating dish to collect the ashes formed. So what do we see? We see that the ribbon starts to burn and gives off a bright light. This is the natural chemical reaction when magnesium comes into contact with fire. We also had to observe the ashes which were flaky and white in colour after it was burnt.

Next, we had to answer a question on the whether due to the Bunsen flame, a new substance has formed and why it has occurred. My answer was as follows:

Yes. Oxygen has reacted with magnesium under higher temperature and also due to the heat it has broken the chemical bonds between the magnesium ribbon and also, the appearances of the magnesium ribbon has totally changed.

This means that oxygen has reacted with magnesium to create magnesium oxide, the white substance formed. :O

How about reacting an element with a compound? Well, our next experiment tells us more. First, we had to place half a spatula of iron fillings in a test-tube. Next, we had to add dilute sulfuric acid to a depth of about 2 cm and record our observations. My observation was that the mixture started to bubble and there were bubbles of colourless gas rising from the iron fillings. So did it change into a new substance and why so? Well, it has indeed changed into a new substance and of course, the reason is that there was a change in appearance and also that heat was involved to break the chemical bonds and form new ones as well.

Last but not least is to react two compounds.So what do we do? First, we place sodium chloride solution in a test-tube to a depth of about 2 cm and then using a dropper, add lead (II) nitrate solution slowly to the test-tube. you will observe that white precipitate formed.

So what exactly can we conclude from this experiment? We now know how the different compounds are formed. :D