Straight to Vapour
Solids that skip the liquid state.
What this lesson covers
Why it matters
Leave a ball of camphor in a cupboard for a week and it slowly shrinks away, filling the shelf with its smell. It never melted into a puddle first, it just vanished into the air.
Predict first
A few crystals of iodine are gently warmed in a dish. Purple fumes rise but no liquid is left behind. What happened to the solid iodine?
Some solids change directly into vapour on heating, without becoming liquid first. This is called sublimation.
- It melted into a liquid, then boiled
- It changed straight from solid to vapour — correct
- It simply disappeared into nothing
- It turned into a new solid
What you do
Sort each solid: does it SUBLIME (solid straight to vapour) or does it MELT first (solid to liquid)?
Check yourself
Sublimation is best described as a change from:
In sublimation a solid turns directly into vapour on heating, without passing through the liquid state.
A mixture of ammonium chloride and common salt can be separated by heating. Which property makes this work?
Ammonium chloride sublimes on heating and can be collected as vapour, while the salt is left behind. So sublimation separates them.
When the purple iodine vapour touches a cold surface, what forms on it?
On cooling, the vapour changes directly back to solid iodine crystals. This deposition is the reverse of sublimation.
- Solid directly to vapour — correct
- Solid to liquid to vapour
- Liquid to solid
- Gas to liquid
- Ammonium chloride sublimes but salt does not — correct
- Salt sublimes but ammonium chloride does not
- Both dissolve in water equally
- Salt is magnetic
- Solid iodine crystals — correct
- A pool of liquid iodine
- Water droplets
- Nothing at all