In this Activity, we will separate camphor from sand by heating, and watch a solid turn into vapour without ever becoming a liquid.
Materials needed
A mixture of crushed camphor (kapoor) and sand, a spatula, a clean dry china dish, a tripod stand with wire gauze, a clean dry glass funnel, a cotton plug, and a burner.
Procedure
1. Take a spatula full of the mixture of crushed camphor and sand and put it into a clean, dry china dish. Place the dish on the wire gauze on the tripod stand.
2. Take a clean, dry glass funnel and plug its nozzle with cotton.
3. Keep this funnel inverted over the china dish.
4. Light the burner and place it under the wire gauze.
5. Heat the china dish gently for a few minutes.
6. Observe the inner wall of the funnel carefully. Do you notice any solid deposits?
Observation
White, solid camphor deposits appear on the inner wall of the funnel, while all the sand remains behind in the china dish.
Explanation
Camphor, on heating below its melting point, changes directly from the solid state to the vapour state without passing through the liquid state — this is
sublimation
. When those vapours strike the cool walls of the funnel, they turn back into a solid without becoming a liquid first — this is
deposition
. Sand does not sublime on heating, so it stays in the dish, and pure camphor collects on the funnel.
Camphor sublimes and separates from sand because sand does not sublime on heating.
→ The cotton plug stops the vapour escaping, so all of it condenses on the funnel wall.
◆ Summary
Camphor and sand are heated under an inverted funnel
Camphor sublimes and deposits on the cool funnel wall
Sand does not sublime and stays in the china dish
What exactly is sublimation?
Normally versus in sublimation
Normally
Solid → Liquid → Vapour
the middle state does come
In sublimation
Solid → Vapour
the liquid state never comes
↓
Camphor is one such exceptional substance
on cooling, the vapour goes straight back to solid — that is deposition
Normally, heating a solid first melts it into a liquid and then turns it into vapour.
Camphor never passes through that middle liquid stage. Heated
below its melting point
, it goes straight from solid to vapour.
Sublimation
is a solid changing directly into vapour without becoming a liquid.
Deposition
is the reverse — vapour cooling straight back into a solid, again without becoming a liquid.
Definition
Sublimation
is the process in which a solid changes directly into the vapour state without passing through the liquid state. The reverse process, vapour turning directly into solid, is called
deposition
.
What else can be used in place of camphor?
Any other
sublimable substance
— one that goes from solid straight to vapour on heating.
Naphthalene
is one, and it behaves exactly like camphor in this activity.
Solid carbon dioxide, called
dry ice
, also sublimes. It is used for ice cream storage.
Dry ice is extremely cold, about
−78.5 °C
, and it turns directly into a cold gas without melting, so no wetness or moisture is produced.
As it turns into gas it absorbs heat from all around it, which keeps the inside of the storage box extremely cold for a long time.
Is sublimation different from evaporation?
Evaporation
Sublimation
Used for homogeneous solutions
Used for heterogeneous mixtures
The solvent is a liquid and the solute is generally a solid
Both substances are solids, and one of them is sublimable
On heating, the liquid turns into vapour and the solid solute is left behind
On heating, the sublimable solid turns straight into vapour and the other solid is left behind
Example — salt from sea water using the sun's heat
Example — camphor from sand, as in Activity 5.7
Yes, the two are completely different.
In
evaporation
, the sun's heat turns the water of sea water into vapour and the salt is left behind as a solid.
In
sublimation
, the sublimable solid itself becomes vapour, and the non-sublimable solid is left behind exactly as it was.
Pause and Ponder
🤔 Pause and Ponder — Question 8
8. Is sublimation different from evaporation? Justify.
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Answer
Yes, the two are completely different processes.
Explanation
Point
Evaporation
Sublimation
Type of mixture
Homogeneous solutions
Heterogeneous mixtures
What is mixed
A liquid solvent and a generally solid solute
Two solids, one of which is sublimable
What turns into vapour
The liquid solvent
The sublimable solid itself
What is left behind
The solute, as a solid
The non-sublimable solid, unchanged
Example
Salt left behind when sea water evaporates in the sun
Camphor separated from sand in Activity 5.7
In evaporation a liquid becomes vapour; in sublimation a solid becomes vapour directly, skipping the liquid state.
Is it possible to dissolve one metal in another?
Making an alloy
At room temperature
metals are solid and do not dissolve into each other
↓
Melt them at a high temperature
now in liquid form, they mix completely
↓
A homogeneous solution is formed
then it is cooled
↓
It solidifies into a new material that looks like a single metal — an alloy
Metals do
not
dissolve into each other at room temperature.
But when melted at high temperature they mix completely and form a
homogeneous solution
.
On cooling, it solidifies into a new material that looks like a single metal.
Physical methods, such as filtering or using a magnet,
cannot
separate the components of an alloy.
Definition
A homogeneous mixture of two or more metals, or of a metal and a non-metal, is called an
alloy
.
Why do we make alloys, and what are some examples?
Alloys are made so that we get materials that are
stronger, more rigid and more corrosion-resistant
than pure metals — that is, protected from rust.
Alloy
Made of
Where we see it
Brass (pital)
About 80 % copper and 20 % zinc
Utensils, fittings, musical instruments
Bronze (kansa)
About 80 % copper and 20 % tin
Statues, bells, medals
Stainless steel
Iron with carbon (about 0.03–0.8 %), chromium (16–18 %), nickel (10.0–14.0 %) and molybdenum (2.0–3.0 %)
Kitchen utensils that stay strong and never rust
✅ Test Yourself
Which liquid comes out first when a separating funnel's stopcock is opened, and why?
View Answer
Hide Answer
The denser liquid, because it settles at the bottom and gravity drains it out first. In the oil–water case, that is the water.
Name two sublimable substances.
View Answer
Hide Answer
Camphor and naphthalene. Solid carbon dioxide (dry ice) also sublimes.
What is the reverse of sublimation called?
View Answer
Hide Answer
Deposition — vapour turning directly back into solid without becoming a liquid.
Can an alloy be separated by physical methods?
View Answer
Hide Answer
No. An alloy is a homogeneous mixture, and physical methods such as filtering or using a magnet cannot separate its components.
📝 Summary - What we have learnt
Two
immiscible liquids
are separated with a
separating funnel
, using the difference in their densities.
Most gas mixtures are homogeneous, but
smoke, fog and dust
are heterogeneous mixtures with a gas as one component.
Sublimation
separates a sublimable solid, such as camphor, from a non-sublimable one, such as sand; the reverse process is
deposition
.
A homogeneous mixture of metals is an
alloy
— brass, bronze and stainless steel — and it cannot be separated by physical methods.
CA Maninder Singh is a Chartered Accountant with 16+ years of practical experience and 20+ years of teaching experience. At Teachoo, he simplifies Accounts, Tax and GST with step-by-step examples so students can apply concepts confidently in exams and real life.
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