What is Deliquescence?

S6-SA4-0361

Grade Level:

Class 10

AI/ML, Physics, Biotechnology, Space Technology, Chemistry, Engineering, Medicine

Definition

What is it?

Deliquescence is the property of certain solid substances to absorb moisture from the atmosphere until they dissolve in the absorbed water and form a solution. These substances essentially 'melt' into a liquid just by sitting in the air, without needing to be heated.

Simple Example

Quick Example

Imagine leaving a packet of common salt (which is mainly sodium chloride) open on your kitchen counter during the monsoon season. You might notice it getting a bit clumpy, but it usually doesn't turn into a puddle. Now, imagine leaving a small piece of calcium chloride (like the kind used in some moisture absorbers) open. After a few hours, especially on a humid day, it will start looking wet and eventually turn into a liquid solution. That's deliquescence in action!

Worked Example

Step-by-Step

Let's say you have 10 grams of a deliquescent substance, Substance X, in a small dish in a very humid room. The substance starts absorbing water vapor from the air.

Step 1: Initial observation: Substance X is a dry solid powder, weighing 10g.
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Step 2: After 1 hour: You notice the surface of Substance X looks slightly damp and sticky. It has absorbed some water, but is still mostly solid.
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Step 3: After 3 hours: More water has been absorbed. The substance is now a thick paste, and you can see small droplets of liquid forming around the edges. Its weight might now be around 12g (10g original + 2g absorbed water).
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Step 4: After 6 hours: Substance X has completely turned into a clear liquid solution. All the solid has dissolved in the water it absorbed from the air. Its weight might now be 15g (10g original + 5g absorbed water).
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Step 5: Conclusion: Substance X is deliquescent because it absorbed enough moisture from the air to completely dissolve and form a solution without any external water being added.

Answer: The substance transformed from a solid to a liquid solution by absorbing atmospheric moisture.

Why It Matters

Understanding deliquescence is crucial in fields like Chemistry for storing chemicals correctly and in Engineering for designing packaging that protects products from moisture. It's also important in Medicine for formulating drugs that remain stable. Knowing this helps scientists and engineers prevent damage to materials and ensure product quality.

Common Mistakes

MISTAKE: Confusing deliquescence with efflorescence. | CORRECTION: Deliquescence is when a substance absorbs moisture and dissolves. Efflorescence is when a hydrated salt loses its water of crystallization to the atmosphere and turns into a powder.

MISTAKE: Thinking all substances that absorb water are deliquescent. | CORRECTION: Many substances absorb water (they are hygroscopic), but only those that absorb enough water to dissolve and form a solution are deliquescent.

MISTAKE: Believing deliquescent substances melt due to heat. | CORRECTION: Deliquescent substances turn into a liquid by absorbing water from the air, not by melting due to an increase in temperature.

Practice Questions

Try It Yourself

QUESTION: Which of these is most likely to be a deliquescent substance: common table salt, calcium chloride, or sand? | ANSWER: Calcium chloride

QUESTION: A solid substance, when left open in a humid room, completely converts into a liquid solution after a day. What property does this substance exhibit? | ANSWER: Deliquescence

QUESTION: Describe two conditions that would favor a deliquescent substance turning into a solution more quickly. | ANSWER: High humidity in the atmosphere and a higher surface area of the deliquescent substance exposed to the air.

MCQ

Quick Quiz

Which of the following phenomena describes a solid substance absorbing moisture from the air and dissolving to form a solution?

Efflorescence

Deliquescence

Sublimation

Evaporation

The Correct Answer Is:

Deliquescence is specifically the process where a solid absorbs enough atmospheric moisture to dissolve and form a solution. Efflorescence is the opposite, losing water; sublimation is solid to gas; and evaporation is liquid to gas.

Real World Connection

In the Real World

You might have seen small packets of silica gel inside new shoe boxes, electronic gadgets, or medicine bottles. While silica gel is hygroscopic (absorbs moisture), some industrial moisture absorbers, especially for very damp areas, use deliquescent salts like calcium chloride. These salts literally 'drink' the excess humidity from the air, turning into a liquid, which helps protect goods from moisture damage during storage or transport, especially in India's diverse climate.

Key Vocabulary

Key Terms

Deliquescence: The property of absorbing atmospheric moisture to dissolve and form a solution | Hygroscopic: The property of absorbing moisture from the air | Humidity: The amount of water vapor in the air | Solution: A homogeneous mixture formed when one substance dissolves in another

What's Next

What to Learn Next

Now that you understand deliquescence, you can explore 'Hygroscopy' and 'Efflorescence'. These concepts are closely related and will help you differentiate between different ways substances interact with moisture in the atmosphere.