🌡️ 2. Water as a Temperature Stabilizer

• Internal Stability: Our bodies (about 70% water) don’t heat up or cool down too quickly.
• Environmental Stability: Oceans and lakes heat up slowly in summer and cool slowly in winter—this keeps Earth’s climate moderate.

🌍 That’s why coastal areas have milder temperatures than deserts or inland areas.

💨 3. Heat of Vaporization

👉 What is it?

The amount of heat needed to change 1 kg of liquid water into vapor (gas).

• For water, it’s 574 Kcal/kg. That’s a lot of energy!

🚿 Importance in Life:

• When sweat evaporates from our skin, it takes away a lot of heat from our body, helping us cool down.
• When plants transpire (release water through leaves), they also cool themselves.

💧 Every gram of water that evaporates removes 574 calories of heat from the body or plant!

💡 Analogy:

It’s like boiling tea—it takes a long time because water absorbs lots of heat before turning into steam. That’s water’s cooling power in action!

🤝 4. Cohesion and Surface Tension

🌊 What is Cohesion?

• Cohesion means same-type molecules sticking together.
• Water molecules are strongly attracted to each other because of hydrogen bonds.

🧠 Mnemonic:
CO-CO: Cohesion = Connection of the Same
Like co-workers (same company) sticking together!

🌱 Importance in Plants:

• Water molecules stick together and form a continuous column from roots to leaves.
• When water evaporates from leaves, it pulls more water up through the xylem vessels.

🌿 This is how plants drink water against gravity—no heart, no pump—just cohesion!

🕸️ Surface Tension:

Water acts like it has a thin invisible skin on its surface.
That’s why some insects like water-striders can walk on water.

• Surface tension is also due to hydrogen bonding, holding molecules tightly at the surface.

⚡ 5. Ionization of Water

⚛️ What Happens?

Water molecules can split (ionize) into:

• H⁺ (Hydrogen ion)
• OH⁻ (Hydroxyl ion)

At room temperature:

• Only 1 in 550 million water molecules ionizes.
• So, in pure water, both H⁺ and OH⁻ are 10⁻⁷ moles/litre.

🧪 Biological Importance:

• These ions are very reactive.
• They participate in important chemical reactions like hydrolysis (breaking large molecules).
• They help determine pH (acidity or alkalinity) of our body fluids.

⚠️ Enzymes (biological helpers) work best at specific pH values. If pH changes, enzymes may not work properly.