4.6 Reactivity of Metals

Key Concept: Reactivity varies among different metals.
Gold as an Example:
  - Unreactive element; can be found on the Earth's surface.
  - Contrast with Iron:
    - Requires mining and smelting processes.
Reason for Reactivity Differences:
- Linked to how easily metals give up their outer shell electrons.
- The ease of losing electrons varies; e.g., losing one electron is easier than losing two.
Reactions with Acids:
- When metals react with acids, electrons are transferred to hydrogen ions in the acid, resulting in the formation of positive metal ions and hydrogen gas.
- These reactions are classified as displacement reactions.
Chemical Equation:
- A general representation of the reaction is:
- $ext{Metal} + ext{Hydrochloric Acid} <br>ightarrow ext{Salt} + ext{Hydrogen Gas}$

Objective of Lesson 4.6:
- Relate the reactivity of metals to their electron shell structure and periodic table location.

Purpose:
- Predict how metals will react with acids based on their position in the activity series.
Activity Series Order (from most to least reactive):
- Lithium (Li) → Potassium (K) → Sodium (Na) → Calcium (Ca) → Magnesium (Mg) → Aluminum (Al) → Manganese (Mn) → Chromium (Cr) → Zinc (Zn) → Iron (Fe) → Nickel (Ni) → Tin (Sn) → Lead (Pb) → Hydrogen (H) → Copper (Cu) → Mercury (Hg) → Silver (Ag) → Gold (Au) → Platinum (Pt).
Observations:
  - Metals like lithium, potassium, sodium, and calcium are highly reactive; they can react with water to produce hydrogen gas.
  - Metals such as copper, mercury, and silver do not react with acids to produce hydrogen gas.
  - Gold and platinum are among the least reactive metals.

First Example:
- Sodium (Na) as a highly reactive metal loses an electron to become $ext{Na}^+$ (a stable ion), displacing hydrogen in the reaction with hydrochloric acid to produce hydrogen gas:
- $2 ext{Na}(s) + 2 ext{HCl}(aq) <br>ightarrow ext{H}_2(g) + 2 ext{NaCl}(aq)$
Second Example:
- Iron (Fe) is more reactive than copper (Cu) and can displace copper from its sulfate solution:
- $ext{CuSO}_4(aq) + ext{Fe}(s) <br>ightarrow ext{Cu}(s) + ext{FeSO}_4(aq)$
Application of Activity Series:
- Helps in comparing the reactivity of metals during various reactions, such as displacement reactions.

Significance of Metals in Ancient Civilizations:
- The development of better weapons through metals like copper, tin, and iron enabled the success of ancient civilizations.
Smelting Process:
  - A chemical process involving carbon reacting with molten ore to isolate pure metal.
  - Ancient civilizations like the Mesopotamians utilized smelting over 5000 years ago to produce bronze by combining copper and tin.
  - Bronze was favored for its corrosion resistance and hardness.
Roman Advancements:
- Romans used smelting to extract iron, which was further strengthened through hammer pounding, producing formidable weapons and armor, contributing to their dominance for over 400 years.

Importance of Evaluation in Experiments:
- Experimental designs may have limitations affecting results; it’s critical to evaluate these limitations.
Example of Evaluation Table:
- A table (Table 4.16) can be constructed to assist in identifying limitations, their effects on dependent variables, and strategies for improvement.
- E.g., if less than 50 mL of water is added during boiling, the required time will be less; recommended improvement includes using precise measuring equipment like a pipette.

Investigation 4.6: Investigating the reactivity of metals.
- Emphasizes the observation of metal reactions with acids.
Investigation 4.7: Quantifying reactivity through measurements of different metals.

Questions 1 to 5 provided on the following page to assess understanding of the concepts discussed.