K

1. A 1.1 SL Water

A 1.1 – Water

  • Essential for Life

    • What physical and chemical properties of water make it essential for life?

    • Challenges and opportunities of water as a habitat.

A1.1.1 Water as the Medium for Life

  • The first cells originated in water; it is the medium for most life processes.

  • Polarity in water molecules results from unequal sharing of electrons.

  • Hydrogen bonding occurs between water molecules due to polarity, leading to various interactions essential for life.

A1.1.2 Hydrogen Bonds

  • Represent the interactions between water molecules.

  • Hydrogen bonds form due to polar covalent bonds, stabilizing water's structure and properties

    • Notation: Polarization indicated when drawing water molecules.

A1.1.3 Cohesion and Tension in Water

  • Hydrogen bonding creates cohesion; contributes to water transport in xylem and surfaces as habitats (e.g., surface tension).

  • Transport in Plants: Water moves under tension in xylem due to cohesive forces.

  • Habitat Creation: Surface tension allows organisms to utilize water surfaces.

A1.1.4 Adhesion Properties

  • Water adheres to polar or charged materials, affecting organisms.

  • Capillary Action: Demonstrated in plant cell walls and soil; allows water movement in narrow spaces.

A1.1.5 Solvent Properties of Water

  • Water dissolves many hydrophilic molecules.

  • Enzymes catalyze reactions in an aqueous environment.

  • Importance of hydrophobic molecules: Some cell functions depend on insoluble materials.

A1.1.6 Physical Properties of Water

  • Buoyancy, Viscosity, Thermal Conductivity, Specific Heat: Essential for aquatic animals like the black-throated loon (Gavia arctica) and ringed seal (Pusa hispida).

  • Physical properties create unique environments favoring certain adaptations in organisms.

Water Originated in Life

  • Water allowed the first cells to develop membrane-enclosed spaces for essential reactions.

  • Interaction of molecules in water underpins life processes.

Earth's Water Distribution

  • Over 70% of Earth's surface is covered by water, primarily in oceans, contributing to life forms.

Importance of Water in Cells

  • Water comprises cytoplasm, where metabolic reactions happen—enzymes depend on molecular interactions facilitated by water.

  • Water as a fluid compartment: It aids cellular transport and maintains metabolic stability.

Evolution of Cells and Water Environments

  • Early cells evolved membranes to maintain cytoplasmic separation from ocean water.

  • Cell structures are primarily aquaeous; optimal chemical reactions occur in watery environments.

Polar Covalent Bonds and Water Structure

  • Water molecules possess polar covalent bonds due to electron distribution; leads to hydrogen bond formation.

    • Electrostatic interactions generate partial charges (δ+ on H, δ- on O).

Drawing Water Molecule Structures

  • Illustrate water molecule structure to highlight electrons and covalent bonds.

  • Concepts of hydrogen bonds depicted through molecule interactions.

Multiple Water Molecules Representation

  • Illustrate interactions demonstrating weak hydrogen bonds forming between partial charges of water molecules.

Biological Properties of Water

  • Cohesion and adhesion lead to water's functional roles in ecosystems, explaining habitat dynamics.

Surface Tension Formation in Water

  • Surface tension arises from cohesive forces caused by hydrogen bonding, enabling droplet formation.

Habitats Supported by Surface Tension

  • Surface tension strong enough to support small insects; allows organisms like pond skaters and mosquito larvae to thrive.

Water Transport in Plants

  • Water's cohesion allows upward movement under tension, crucial in the process of transpiration.

Adhesion Effect on Water Movement

  • Attraction between polar water molecules and surfaces leads to movement in narrow tubes (capillary action).

  • Water spreads through narrow spaces, critical for plant water uptake.

Resurrection Plants and Capillary Action

  • Example of the rose of Jericho utilizes capillary action for rapid hydration during rehydration events.

Solvent Properties of Water

  • Water's polarity attracts ions, facilitating dissolution of ionic compounds like NaCl.

  • Key to metabolic reactions—enzyme activity in aqueous solutions.

Importance of Hydrophilic and Hydrophobic Molecules

  • solution dynamics

  • Polar (hydrophilic) molecules essential for life processes, while nonpolar (hydrophobic) substances require special transport mechanisms like lipoproteins.

Specific Cases of Molecule Solubility

  • Examples include glucose, amino acids, and fats emphasizing polar interactions and transport mechanisms through blood plasma.

Physical Properties of Water

  • Buoyancy: Provides an insulation layer (ice) assisting winter survival.

  • Viscosity: Crucial for how organisms move through water; impacts swimming and energy expenditure.

  • Thermal Conductivity and Specific Heat: Vital for maintaining stable aquatic habitats amidst temperature fluctuations.

Comparison of Air and Water Properties

  • Significant differences in properties affect living adaptations in animal species.

  • Case Study: Ringed seal vs. black-throated loon adaptations to buoyancy, viscosity, thermal conductivity, and specific heat.