Which of the following metals reacts slowly with cold water?

Step 1: Analyze the question We need the metal that reacts slowly with cold water. This is about the reactivity series.

Step 2: The concept Metals react with water according to their position in the reactivity series:

• Potassium, Sodium: react violently with cold water (the hydrogen often ignites).
• Calcium: reacts steadily or moderately with cold water, giving bubbles of hydrogen and calcium hydroxide. It is slower than potassium and sodium.
• Magnesium: reacts very slowly with cold water, but readily with steam.
• Zinc, Iron: do not react with cold water. Iron reacts only with steam (and rusts slowly with water and air over a long time).
• Copper, Silver, Gold: do not react with water at all.

Step 3: Check each option

• A. Iron: no real reaction with cold water, only slow rusting with oxygen present. It is not a typical "reacts with cold water" metal.
• B. Silver: no reaction.
• C. Calcium: reacts with cold water, but more slowly than potassium: Ca + 2H₂O → Ca(OH)₂ + H₂↑
• D. Potassium: reacts violently: 2K + 2H₂O → 2KOH + H₂↑

Step 4: Answer Among the options, calcium is the only metal that actually reacts with cold water, and it does so slowly compared with potassium.

Answer: C. Calcium

Exam tip: Remember the order "Please Stop Calling Me A Zebra In Lagos Hot Club Silver Gold" (Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Lead, Hydrogen, Copper, Silver, Gold). Potassium and sodium are violent, calcium is moderate or slow, and metals below magnesium do not react with cold water.