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๐ฌ Think about it
Pour mustard oil into water and they refuse to mix — the oil floats on top. Since they form clear layers, we can drain them apart. How? With a separating funnel. Let us try.
What are immiscible liquids?
- They are liquids that do not mix together.
- They form separate layers, like oil and water.
- They are examples of heterogeneous mixtures.
Example:
Mustard oil floats as the upper layer and water stays below.
In this Activity, we will use a separating funnel to separate mustard oil from water.
Procedure
1. Pour a mixture of 5 mL mustard oil and 20 mL water into a 50 mL separating funnel.
2. Let it stand undisturbed. You see two separate layers form (Fig. 5.16). The yellow mustard oil is on top and water below, because oil is lighter.
3. Open the stopcock slowly to collect the lower water layer carefully into a container.
4. Close the stopcock when the water is almost fully drained.
5. Collect and discard the small middle portion that may contain both liquids.
6. Collect the oil layer separately by opening the stopcock again.
2. Let it stand undisturbed. You see two separate layers form (Fig. 5.16). The yellow mustard oil is on top and water below, because oil is lighter.
3. Open the stopcock slowly to collect the lower water layer carefully into a container.
4. Close the stopcock when the water is almost fully drained.
5. Collect and discard the small middle portion that may contain both liquids.
6. Collect the oil layer separately by opening the stopcock again.
โ Summary
- Pour oil and water in a funnel.
- Let layers form.
- Drain the lower water layer.
- Collect the oil separately.
Can a gas be part of a heterogeneous mixture?
- Most gas-gas mixtures are homogeneous, since gases mix evenly.
- But some mixtures with a gas are heterogeneous.
- Smoke (solids in air), fog (liquid droplets in air) and dust are heterogeneous.
Example:
A hydrogen-oxygen mixture (rocket fuel) is homogeneous, but smoke is heterogeneous.
Important Points
- Immiscible liquids do not mix and form separate layers.
- A separating funnel separates them by their different densities.
- Smoke, fog and dust are heterogeneous mixtures with a gas.
โ Test Yourself
-
What apparatus separates two immiscible liquids?
View Answer
A separating funnel. -
Why does mustard oil sit on top of water?
View Answer
Oil is lighter (less dense) than water. -
Give one heterogeneous mixture that contains a gas.
View Answer
Smoke, fog or dust in air.
Important Definitions
- Immiscible liquids — liquids that do not mix and form separate layers.
- Separating funnel — apparatus that separates immiscible liquids by their different densities.
๐ NCERT Question 5 — The label on a
Cooking oil mixed with water — will it form a layer, which is on top, and how do you separate them?
View Answer →
