Chemistry: Water

Importance of Water

• Life is impossible without water.
• Only 2-5% of water is fresh and usable.
• 97% of water is salty and 3% is fresh water.
• Only 0.7% of water is usable, which is available in rivers and lakes.

Physical and Chemical Properties of Water

• The boiling point of water is 100°C at normal pressure.
• At higher altitudes, the atmospheric pressure is lower, so the boiling point of water decreases.
• The freezing/melting point of water is 0°C.
• The density of water is highest at 4°C, 1 g/cm³.

Unique Characteristics

• Unique Expansion: Water contracts at 4°C and expands at 0°C.
• Latent Heat: Heat is required to melt ice.
• High Specific Heat Capacity: It takes 4.2 J of energy to increase the temperature of one gram of water by one degree.
• Universal Solvent: Water can dissolve many substances.

Uses of Water

• As a coolant: Used in radiators and coolers.
• Solutions: Homogeneous mixtures consisting of solvent and solute.
• Crystallization: A process through which crystals are formed.

Hardness in Water

• Temporary hardness: Caused by bicarbonates.
• Permanent hardness: Caused by sulfates and chlorides.

Saponification

• Soap works less effectively in hard water.
• Detergents are more effective.

Water Purification

• RO (Reverse Osmosis) is used as a purifier.
• Being a universal solvent, water can remove dissolved impurities.

Gas Solubility

• Dissolved oxygen and nitrogen are present in water.
• Dissolved oxygen is crucial for fish.

Crystals and Hydrates

• Hydrated substances contain water molecules.
• Behaviors such as deliquescence and efflorescence occur.

Important Tips

• Water should be used efficiently.
• Blue crystals are made of copper sulfate.
• Drying agents are used to absorb moisture.

Final Notes

• It is important to understand the solubility and unique properties of water.
• By revising lecture notes, one can gain in-depth knowledge about water.