12.2.1 Distilled Water

This topic explains distilled water — water purified by distillation — and its properties and uses.

Definition

Distilled water is water purified by distillation.

Simple explanation: Distilled water is water that has been boiled, evaporated, and condensed back into liquid, leaving impurities behind.

Main Idea

• Heating water to boiling point.
• Collecting the vapours.
• Condensing them back into liquid.

The impurities are left behind. Distilled water is free of any contaminants.

• Electrical conductivity is very low.
• pH is 7 (neutral).

Simple explanation: Distilled water is very pure — it has no dissolved impurities.

Core Concept

The Distillation Process

Simple explanation: Boil water → collect steam → cool steam back to water → impurities left behind.

Properties of Distilled Water

Detailed Explanation

How Distillation Works

• Heating: Water is heated to its boiling point (100 °C).
• Evaporation: Water molecules turn into vapour (steam). Impurities (dissolved salts, minerals, microbes) do not evaporate — they stay behind in the original container.
• Collection: The water vapour is collected.
• Condensation: The vapour is cooled and condensed back into liquid form.

The result is distilled water — pure water with no dissolved impurities.

Simple explanation: Distillation uses evaporation and condensation to separate pure water from its impurities.

Properties of Distilled Water

• Distilled water contains no dissolved salts, minerals, or microbes.
• All impurities are left behind during distillation.

• Pure water contains very few ions.
• So it conducts electricity very poorly.
• This is why distilled water is used in batteries and laboratory experiments.

• Distilled water is neutral (pH = 7).
• Neither acidic nor basic.

Simple explanation: Distilled water is pure, neutral, and does not conduct electricity well.

Uses in Chemistry

The book gives two main uses:

• Distilled water is usually used in laboratories to prepare chemical reagents and solutions.
• Why? Because it contains no impurities that could interfere with reactions.

• Distilled water is used in the calibration of sensors in analytical instruments, e.g., pH meter.
• Why? Because it is pure and neutral, so it provides a reliable reference.

Simple explanation: Distilled water is used in labs because it has no impurities that could affect experiments.

Distilled Water vs Tap Water

Intermediate Level

Why Distilled Water Has Low Electrical Conductivity

• Pure water contains very few ions (H⁺ and OH⁻ only).
• Ions are needed to carry electric current.
• So pure water conducts electricity very poorly.
• Tap water contains dissolved minerals (ions), so it conducts electricity better.

Simple explanation: No ions → no conductivity. Distilled water has almost no ions.

Why Distilled Water Is Used in Laboratories

• No impurities → no interference with experiments.
• Neutral pH → doesn't affect reactions.
• No dissolved ions → doesn't affect conductivity measurements.
• Consistent quality → reliable results.

Simple explanation: Labs need pure water so that impurities don't affect their experiments.

Distilled Water vs Other Purified Waters

Simple explanation: Different methods produce different types of purified water.

Limitations of Distilled Water

• Cost: Distillation requires energy (heating) — it is expensive.
• Taste: Distilled water can taste "flat" because it lacks minerals.
• Not for drinking: Drinking large amounts of distilled water can leach minerals from the body.
• Storage: Must be stored carefully to avoid contamination.

Simple explanation: Distilled water is great for labs but not ideal for drinking.

Important Points

• - Distilled water: water purified by distillation.
• - Process: heating → evaporation → collection → condensation.
• - Impurities are left behind.
• - Distilled water is free of contaminants.
• - Electrical conductivity is very low.
• - pH is 7 (neutral).
• - Uses:
• - Preparing chemical reagents and solutions in laboratories.
• - Calibration of sensors in analytical instruments (e.g., pH meter).
• - Tap water contains dissolved minerals and gases; distilled water does not.

Remember

• - Distilled water = pure water (no impurities).
• - Made by: boiling → evaporation → condensation.
• - Impurities stay behind.
• - **pH = 7** (neutral).
• - Very low electrical conductivity.
• - Uses: laboratory solutions, calibration of pH meters.
• - Tap water ≠ distilled water.

Common Mistakes

• 1. Thinking distilled water and tap water are the same. Distilled water is pure; tap water contains dissolved minerals and gases.
• 2. Thinking distilled water conducts electricity well. It has very low conductivity because it has very few ions.
• 3. Thinking distilled water has a pH other than 7. Distilled water is neutral (pH = 7).
• 4. Thinking distillation removes only dirt. Distillation removes all dissolved impurities (salts, minerals, microbes).
• 5. Thinking distilled water is good for drinking in large amounts. It can leach minerals from the body.
• 6. Confusing distillation with filtration. Distillation uses evaporation and condensation; filtration uses a physical barrier.

Quick Revision

• Distilled water: water purified by distillation.
• Process of distillation:
• Distilled water is free of any contaminants.
• Electrical conductivity: very low.
• pH: 7.
• Uses in chemistry:

60-Second Revision

• Distilled water = pure water.
• Made by: boiling → condensing.
• **pH = 7** (neutral).
• Very low electrical conductivity.
• Uses: laboratory solutions, calibration of pH meters.
• Warning: distilled water is not the same as tap water — it has no dissolved minerals.