INORGANIC COMPOUNDS-WATER_2ND SEM

Inorganic Compounds

Water

The Molecule that Supports All Life

  • Life on Earth originated in water, crucial for evolution over 3 billion years in aquatic environments.

  • Water covers approximately three-quarters (around 71%) of Earth's surface.

  • Exists in all three physical states: solid (ice), liquid (water), gas (water vapor).

Climate Change Impact on Species

  • Black Guillemot exemplifies threats from climate change, impacting population and ecosystems.

Polar Covalent Bonds in Water Molecule

  • Oxygen is more electronegative than hydrogen, leading to unequal sharing of electrons.

  • Creates polar covalent bonds, resulting in a polar molecule with uneven charge distribution, essential for hydrogen bonding.

Hydrogen Bonding in Water

  • Hydrogen bonds form between partially positive hydrogen atoms and partially negative oxygen atoms of different molecules.

  • These bonds are weak (1/20th strength of covalent bonds) and constantly forming and breaking.

Water as an Excellent Solvent

  • Water's polarity and hydrogen bonding make it the “universal solvent.”

  • Substances that dissolve in water are hydrophilic; those that do not are hydrophobic.

  • Hydrogen bonds are stronger collectively than ionic bonds, facilitating uniform dispersion of solutes like NaCl.

Emergent Properties of Water

  • Four emergent properties that support life: Cohesion, Adhesion, Temperature regulation, and High solvent capabilities.

Cohesion and Adhesion of Water Molecules

  • Cohesion: Hydrogen bonds hold water molecules together, aiding processes like water transport in trees.

  • Adhesion: Water clings to other substances, allowing it to move against gravity in plant cell walls.

  • Trees can transport water over 100 meters due to cohesion and adhesion.

Surface Tension of Water

  • Surface tension arises from strong hydrogen bonds, enabling some organisms to walk on water surfaces.

Temperature Moderation by Water

  • Water absorbs heat from warmer air and releases it to cooler air, acting as a heat bank with minimal temperature fluctuations.

Temperature and Heat

  • Kinetic Energy: Energy of motion in atoms/molecules.

  • Thermal Energy: Total kinetic energy; temperature indicates average kinetic energy.

  • Heat: Thermal energy transfer between bodies.

Caloric Measures

  • A calorie: Heat to raise 1g of water by 1°C.

  • A kilocalorie (kcal): 1,000 calories, often used for food energy.

  • A joule (J): Another energy unit (1 J = 0.239 cal; 1 cal = 4.184 J).

Water's High Specific Heat

  • Specific heat: Heat required to change temperature of 1g of a substance by 1°C.

  • Water has a high specific heat compared to many substances; facilitates stabilization of temperatures.

Life Relevance of Water’s High Specific Heat

  • Large water bodies maintain substantial heat with minimal temperature change, moderating air temperatures in coastal areas.

  • Organisms mainly composed of water can resist temperature changes more effectively than those with less stable liquids.

Evaporative Cooling

  • Evaporative cooling occurs with the transformation of liquid to gas; faster molecules escape even at lower temperatures.

  • Heating increases molecular kinetic energy, accelerating evaporation.

Heat of Vaporization

  • High heat of vaporization: 580 cal is needed to evaporate 1g of water due to hydrogen bonds.

  • Significant for climate moderation and biological processes.

Effects of High Heat of Vaporization

  • High energy for vaporization is crucial for climate and cellular thermoregulation; can cause severe burns from condensing steam.

Importance of Evaporative Cooling

  • Stabilizes temperatures in aquatic ecosystems and prevents overheating in terrestrial organisms as the fastest molecules escape during evaporation.

Ice Density and Environment

  • Water expands upon freezing, allowing ice to float; crystalline structure forms due to hydrogen bonding.

  • Maximum density at 4°C before it expands further.

Importance of Floating Ice

  • Ice's floating ability is crucial; sinking ice would freeze aquatic systems, jeopardizing life.

  • Ice insulates liquid water below, supporting diverse organisms.

Effects of Climate Change on Arctic Ecosystem

  • Climate change leads to significant sea ice melting, impacting various species:

    • Benefitted Species: Increased light and warmer waters promote phytoplankton, aiding Bowhead whales and certain fish.

    • Harmed Species: Polar bears face hunting ground loss, and Pacific walrus experience habitat uncertainty, demonstrating climate change effects on biodiversity.