Metal reactivity
Pop test with water - to determine highly active metals
Pop test with hydrochloric acid - to determine active metals
The same factors were considered when discussing this 'pop' test as the water 'pop' above
Metal displacement reaction in a spot tile between each compound and solution. The solid metal has to be more reactive than the solution for a reaction to occur.
Galvanic cells - this will determine which metals are more reactive than others, similarly to the metal displacement reactions
Description: each metal is placed in a test tube with water, and if the metal reacts with the water, hydrogen is released, causing a 'pop' sound when a match is lit above the test tube, as hydrogen is very flammable.
How much water should be placed in each test tube?
The water should completely cover each metal, so that if a reaction occurs, is it easier to observe.
The same amount of water should be placed in each test tube, as this is a controlled variable.
Will the loudness of the 'pop' differentiate which metals are more reactive than others?
While this might be the case, it is not a reliable method to differentiate which metals are more reactive than others, within the set of metals that mad a 'pop' noise. This is because the loudness of the 'pop' is affected by many different factors, not only the reactiveness of the metal. Additionally, unless a decibel is used, the loudness of the 'pop' cannot be accurately measured, rather it would be subject to opinion.
The loudness of the 'pop' is affected by:
The volume of solute
The reactiveness of the metal
The volume of solvent
The amount of time between the metal and water being combined, and the match being lit
The amount of hydrogen leaked out
How long it takes for each metal to react with water
Whether or not all of the hydrogen produced will ignite
Decision: it was decided to use this pop test to determine which metals are highly reactive. However, only whether or not a 'pop' is heard will be noted, as the loudness of the 'pop' is affected by many other factors that are difficult to control.
What factors need to be controlled?
The concentration of the hydrochloric acid needs to be the same across each test tube, and concentrated enough for a reaction to be observed
Enough hydrochloric acid has to be put in each test tube so that the metal is completely covered by it, in order for a reaction to be observed best
Each test tube needs to be covered for at least 30 seconds, before the match is lit
Controlled variables
The metal has to be completely covered by the solution for a reaction to be easily observed
Enough metal has to be placed on each spot tile so that a reaction can be easily observed
If there is a metal oxide layer on the metal before it is placed in the acid, then it will make the results less reliable, because the oxide layer will protect, making it seem less reactive than it actually is. Therefore, the metals need to be left in the solution long enough for a reaction to be observed, approximately 10 minutes
Each solution has to have an equal concentration, as this is a controlled variable. It needs to be controlled because the type of solute and solvent is the only variable that can be changed.
Notes:
There is no quantitative method or measuring if a reaction has occurred, rather it is based on qualitative observations, but this makes it less reliable
How much solvent should be placed in each test tube
The more reactive metal will be placed at the anode, and the less reactive metal at the cathode, and the electrolyte will have the solution of the metal that the electrode is made out of.
Limitations
Usefulness
Many different galvanic cells need to be set up in order for all the reactivity of the metals to be compared to eachother
There is a quantitative way to measure the whether or not a reaction has occurred, making it more reliable, as it is not affected by subjective observations
Decision: metal displacements will be part of the method.
Decision: galvanic cells will be used, as an electric current can be measured to see if a reaction has occurred
Decision: it was decided to use this pop test to determine what metals are reactive
Materials required:
Dilute hydrochloric acid (approx 100mL)
1 box of matches
Each of the metals in solid form
Liquid solutions of each of the metals
Spatula
8 beakers
14 test tubes
Salt bridge
Ammeter
Electrodes of each metal
Connecting wires
4 spotting tiles