Reactivity series

Aluminium is used in aircraft due to its low density. This reduces the overall weight of the aircraft, improving fuel efficiency and performance.

Aluminium is suitable for overhead cables because it possesses both low density and good electrical conductivity. Low density minimizes the load on support structures, while good conductivity ensures efficient power transmission.

Aluminium is used in food containers due to its resistance to corrosion. This prevents the aluminium from reacting with the food, preserving its quality and safety.

Copper is used in electrical wiring because of its good electrical conductivity and ductility. High conductivity allows for efficient electron flow, and its ductility allows it to be drawn into wires easily.

No, Group 1 metals do not exhibit catalytic behavior. Transition metals are more commonly used as catalysts.

Possible observations include: the potassium moves/floats on the water's surface; it dissolves/disappears as it reacts; bubbles/effervescence/fizzing occurs; a lilac flame is produced; the potassium may explode; the potassium melts/forms a spherical shape.

2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g). This equation shows that potassium reacts with water to produce potassium hydroxide and hydrogen gas.

Transition elements generally have higher melting points compared to Group 1 elements. This is due to stronger metallic bonding.

Transition elements generally have higher densities than Group 1 elements. This relates to the size and arrangement of their atoms.

The solution changes from colourless to orange/brown. This is because bromine is displaced.

In the reaction between chlorine and potassium bromide, bromine is displaced. Chlorine gains electrons and is reduced.

A displacement reaction occurs when a more reactive metal takes the place of a less reactive metal in a compound.

Potassium: reacts very vigorously, producing hydrogen which ignites with a lilac flame. Potassium moves rapidly on the water surface and may explode.

Sodium: reacts vigorously, producing hydrogen. Sodium melts into a ball and moves on the water surface. No flame usually seen.

Calcium: reacts slowly, sinking and producing a steady stream of bubbles (hydrogen). The solution turns milky due to slightly soluble calcium hydroxide.

For Group I: 2K + 2H₂O → 2KOH + H₂ (similar for Na).
For calcium: Ca + 2H₂O → Ca(OH)₂ + H₂

Compare how vigorously metals react with the same reagent (e.g., dilute acid or water):

• More reactive metals react faster, produce gas more quickly, or release more heat
• In displacement reactions, a more reactive metal will displace a less reactive one
• If metal A displaces metal B from solution, A is more reactive than B

Aluminium quickly forms a thin, strong layer of aluminium oxide (Al₂O₃) on its surface when exposed to air. This oxide layer is very resistant to corrosion and prevents further reaction. The aluminium underneath is actually very reactive, but the protective oxide coating makes it appear unreactive. This is why aluminium is used for drinks cans and aircraft despite being above carbon in the reactivity series.