Reactivity of Metals and Reaction Rates

Displacement observations: Magnesium forms a brown coating when reacting with copper solutions (identifying the coating as Copper metal) but shows no change in magnesium sulfate solution.
Reactivity series determination: Magnesium > Aluminium > Metal X > Copper.
Identity of Metal X: Zinc.

Research Question: Determining how the type of metal ( $Mg$ , $Al$ , $Zn$ , $Fe$ , $Cu$ ) affects the rate of reaction ( $\text{cm}^3/\text{s}$ ) when $1.0\,\text{g}$ of metal reacts with dilute hydrochloric acid.
Hypothesis: Magnesium > Aluminium > Metal X > Copper because metals higher in the reactivity series lose electrons more readily to form positive ions.
Variables:
- Independent: Type of metal used ( $Magnesium$ , $Aluminium$ , $Metal X$ , $Copper$ ).
- Dependent: Rate of hydrogen ( $H_2$ ) production per unit time ( $\text{cm}^3/\text{s}$ ).
- Controlled: Concentration of hydrochloric acid, temperature of reactants, surface area of metal, mass of metal used ( $1.0\,\text{g}$ ), and volume of hydrochloric acid ( $25\,\text{cm}^3$ ).

Methodology: $1.0\,\text{g}$ of metal is added to $25\,\text{cm}^3$ of acid in a conical flask; hydrogen gas volume is recorded via gas syringe every $20\,\text{s}$ for a total of $120\,\text{s}$ .
Results and Evidence:
- Magnesium: Reacted most vigorously, producing $74\,\text{cm}^3$ of hydrogen gas after $120\,\text{s}$ .
- Copper: Produced $0\,\text{cm}^3$ of hydrogen gas, showing no visible reaction.
- Conclusion: The acid experiment results support the displacement series order.

Aluminium's Oxide Layer: The presence of an oxide layer caused $Aluminium$ to produce only $35\,\text{cm}^3$ of gas compared to $Metal X$ (Zinc) producing $37\,\text{cm}^3$ , contradicting the expected order. Improvement: Sand the aluminium surface before testing.
Limited Trials: Only one trial per metal was performed, making it difficult to distinguish real differences from random error. Improvement: Conduct at least three trials and calculate a mean.
Gas Loss: Potential hydrogen escape from the apparatus could lead to lower-than-expected volumes. Improvement: Ensure all bungs and gas syringe connections are airtight.