If condensation is observed in the first row of a heating test, what does this indicate about the solid?

• A. It is hydrated.
• B. It is anhydrous.
• C. It is a metal.
• D. It is a carbonate.

Answer: (A)

Condensation during heating shows that water is being released from the solid as steam. This happens when the solid contains water of crystallization, i.e., it is hydrated. When you heat a hydrated salt, the water bound in its crystals is driven off as vapor and then condenses on cooler surfaces as droplets. If the solid were anhydrous, there would be no water to release and no condensation. Metals don’t have water of crystallization, and carbonates decompose to oxides and CO2 rather than releasing water, so you wouldn’t expect condensation from them. So observing condensation points to the solid being hydrated.