Investigation into the Reactivity of Metals.

Investigation into the Reactivity of Metals

Introduction:

In this investigation I have been given a set of results therefore I will not conduct the experiment. However, before I receive the results of the experiment, I am going to make a prediction. After I have made my prediction and received my results I will draw a graph from the results, write up a conclusion and then evaluate the results.

Prediction:

I predict that the four metals of this experiment will come in this order:

Calcium
Magnesium
Zinc
Iron

I made this prediction on the knowledge that I have that the reactivity of any element depends on the size of the atom (this is the number of shells) and the number of electrons on the outer shell. This therefore means that the more shells an atom has, the more reactive it is.

An example of this:

Group II metals

Calcium Magnesium Beryllium

2,8,8,2 2,8,2 2,2

Using the previous example (previous page) it can be said that the further away the electrons are from the nucleus, the easier the electrons can be lost. If calcium is compared to magnesium, it can be seen that the outer electrons in calcium are further away from the nucleus, which in turn means that calcium is more reactive than magnesium.

The Group II elements are all metals, which form 2+ ions and have similar properties such as they all have the same number of electrons in their outer shell. When compared amongst themselves, Calcium is more reactive than Magnesium and Magnesium is more reactive than Beryllium. The reason for this is because Calcium has four shells and the outer electrons are far away from the proton. Due to the distance between the electrons and the proton, there is a less attraction between them and so it will lose these electrons more easily. This also occurs between Magnesium and Beryllium.

Result Table:

Analysis:

The graph, which I plotted, shows the exothermic reaction of the four metals (calcium, magnesium, iron and zinc).

Calcium- The graph shows a very sharp rise in temperature in the first 30 seconds. The highest temperature is 96.2ºc and it is reached in 60 seconds. After that point, the temperature gradually decreases. This therefore means that the reaction was completed in 60 seconds.

Magnesium- The graph shows a steep rise, but the line isn’t as sharp as for the line for calcium. The highest temperature is 82ºc and ...

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Result Table:

Analysis:

The graph, which I plotted, shows the exothermic reaction of the four metals (calcium, magnesium, iron and zinc).

Magnesium- The graph shows a steep rise, but the line isn’t as sharp as for the line for calcium. The highest temperature is 82ºc and it is reached in 90 seconds. After that, the temperature slowly decreases. The reaction took 90 seconds to be completed.

Zinc and Iron are called transition metals. They are more complicated then Group I and Group II metals.

Iron- The temperature starts at 22ºc and goes up by one degree in 30 seconds. It then remains at 23ºc and stays at this temperature until the full time investigated is completed.

Zinc- The temperature starts at 22ºc and very slowly increases over the remaining of the time. After 540 seconds, the temperature went only up to 28ºc.

From the results, it can be concluded that Zinc is more reactive than iron. All of the evidence (results, graph and scientific proof) supported my prediction and based on this I have arranged the metals in this order, starting with the most reactive:

Calcium
Magnesium
Zinc
Iron

The results match my prediction and I had expected this to happen. I had previously justified that calcium is more reactive than (electrons theory) and so I expected these two elements to be the most reactive. I had also done some previous research on iron and zinc in which I had found out that zinc is more reactive than iron. So I then knew that these two would follow calcium and magnesium.

Evaluation:

The procedures, which were carried out in this experiment, were not very good, but the results obtained are accurate and they do support my prediction. They show that calcium is more reactive than magnesium, magnesium is more reactive than zinc and zinc in turn is more reactive than iron.

My graph shows about four slight anomalous results (these anomalous results have been circle on my graph).

Since I didn’t carry out the experiment, I don’t know what might have gone wrong or which mistakes might have been carried out. But these anomalous results could be due to different factors:

Some of the mixture might have been stirred with the thermometer. This would have affected the results because as the mixture is stirred, the particles within it are being moved about. This movement is an additional source of energy and this increase of energy would cause the temperature to rise.
The readings of the thermometer might have been recorded incorrectly. This could be due to human error or the fact that it would have been hard to see the temperature for both zinc and iron, as they were so slow and it would have been hard to see well down a polystyrene container.
There is no way of knowing whether or not the size of the metal particles were the same (i.e. the pieces of zinc could have been finer than the pieces of iron). In weight (same amount of both), small pieces have a greater surface area than large pieces.
As this experiment is a long one (time consuming), it might have been done over days/weeks. This in turn might have had an affect on the experiment as the room temperature might have varied from day to day.

Improvements:

Each experiment could be repeated two or more times and an average reading could be calculated.

A see through container could be used instead of a polystyrene container. This would make the readings easier to record.

A sensor computer programme could also be used in order to get an even more accurate result.

Take even more care to make sure that none of the mixture is stirred. This could be done by not touching the apparatus whilst the experiment is taking place (i.e. not picking the container up etc.).

This experiment could be further investigated by carrying out a displacement reaction experiment. This is where the element, which is the most reactive, displaces the other components.

For calcium:

E.g. calcium + magnesium chloride = calcium chloride +

Magnesium

Calcium + zinc chloride = calcium chloride + zinc

Calcium + iron chloride = calcium chloride + iron

As calcium is the most reactive out of the four metals, it displaces them ( pushed them out and took their place).

Where as, if iron were to be added to calcium chloride, magnesium chloride or zinc chloride there would be no reaction because zinc is the least reactive out of those four metals (zinc, iron, magnesium and calcium).

E.g. Iron + calcium chloride = iron + calcium chloride (no

reaction).

Iron + magnesium chloride = iron + magnesium chloride (no

reaction).

Iron + zinc chloride = iron + zinc chloride (no reaction).

The displacement reaction experiment could also be used with other metals to find out their reactivity.

An experiment involving water could also be done to find out the reactivity of these four metals. Calcium would fizz, less than a Group I metal but more than magnesium (even though it would take a long time). The same principle applies to zinc and iron. When added to water, they would both be significantly slower to react than Group I and Group II metals, but zinc would be more reactive than iron.

Having looked at all of the evidence, (results, graph and scientific proofs) I have arranged the metals in this order, starting with the most reactive: