Chapter 10: Water & Solutions - Key Points

Water Resources

• Surface Water: Streams, lakes, reservoirs; contains sediments & pollutants.
• Groundwater: Generally cleaner but affected by agricultural & industrial seepage.
• Impact of climate change: Extreme droughts and floods affecting availability.

Household Water Usage

• Usage breakdown: Toilet (24%), Shower (20%), Faucet (19%), Clothes Washer (17%), Leak (12%), Other (8%).

Properties of Water

• Essential for life; known as a "Universal solvent."
• Ice is less dense than liquid water, which allows it to float.
• High specific heat: stabilizes climate; retains heat.
• High latent heat of vaporization aids in evaporative cooling (sweating).

Molecular Structure

• Water has a polar covalent bond and a bent molecule structure, leading to cohesiveness.

Density of Water

• Maximum at 4°C; Ice floats due to lower density.
• Supports aquatic life during freezing conditions.

Boiling and Freezing Points

• Boiling point at sea level: 100^{ ext{oC}}.
• Freezing point lowers in the presence of solutes (e.g., salt).

Phase Diagram

• Visualizes changes in water phases with temperature and pressure.
• Latent heat of fusion: 80 ext{ cal/g} at 0^{ ext{oC}}; latent heat of vaporization: 540 ext{ cal/g} at 100^{ ext{oC}}.

Aqueous Solutions

• Solute: substance dissolved; Solvent: substance in greater amount (usually water).
• Unsaturated: can dissolve more solute; Saturated: max solute dissolved.

Solubility and Temperature

• Solubility generally increases with temperature for solids.

Concentration Measurement

• Molarity (M): moles of solute per liter of solution.

Supersaturated Solutions

• Formed by cooling unsaturated solutions; may require a seed crystal to induce crystallization.

pH Scale

• Measures acidity/basicity (pH range: 0-14); neutral at pH = 7.
• Adding acid increases [H_3O^+] (lowers pH); base increases [OH^-] (raises pH).

Acid & Base Properties

• Acid: proton donor; Base: proton acceptor.
• Neutralization occurs when acids and bases mix.

Common pH Examples

• Understanding of various substances in terms of their pH levels is crucial.