Water and Life Lecture Flashcards

Water and Life

Opening Questions

  • How big or small can we go in the levels of life?

    • Chart the progression of complexity from:

    • Atom

    • Organism

    • Ecosystem

  • Can you go any bigger? Or smaller?

    • Atom is the fundamental unit of matter, the smallest unit of an element retaining all properties of that element.

Composition of Atoms

  • All matter is composed of atoms, which are made of smaller particles.

  • Subatomic Particles:

    • There are three types: neutrons, protons, and electrons.

    • Atoms: Composition

    • Protons:

      • Positive charge.

      • Located in the nucleus.

      • Number of protons determines the chemical element.

    • Neutrons:

      • No charge.

      • Located in the nucleus.

      • Number of neutrons determines the isotope.

    • Electrons:

      • Negative charge.

      • Orbit nucleus at high speeds.

      • Little mass, determines ion state and chemical reactivity.

    • Nitrogen Atom Composition:

    • 7 protons, 7 neutrons, 7 electrons.

Isotopes and Ions

  • Isotopes: Variants of an element that differ in their number of neutrons.

    • Protons identify element; isotopes vary neutron count.

    • Less stable isotopes may decay, emitting radiation.

    • Nitrogen-15 Isotope:

    • 7 protons, 8 neutrons, 7 electrons.

Ions

  • Ions result from an atom gaining or losing electrons, resulting in an electric charge.

  • Example: If nitrogen gains 3 electrons, it forms a negatively charged ion:

    • Nitrogen Ion:

    • 7 protons, 8 neutrons, 10 electrons.

Chemical Bonds

  • Atoms bond to form molecules, primarily through:

    1. Covalent Bonds: Sharing electrons.

    2. Ionic Bonds: Transferring electrons, creating charged atoms.

  • Types of Covalent Bonds:

    • Nonpolar Covalent Bonds: Equal sharing of electrons.

    • Polar Covalent Bonds: Unequal sharing of electrons.

Water and Life

Concept Overview

  • Water as a Biological Medium:

    • Essential for life, existing in all three physical states (solid, liquid, gas).

    • The structure of water molecules allows interaction with other molecules.

    • Unique emergent properties make Earth suitable for life.

Polar Covalent Bonds and Hydrogen Bonds

  • In water molecules, electrons in polar covalent bonds spend more time near oxygen, creating a polar molecule.

  • Polarity Effects:

    • Uneven charge distribution allows hydrogen bonding between water molecules.

Emergent Properties of Water

  • Four Properties of Water:

    1. Cohesive behavior.

    2. Ability to moderate temperature.

    3. Expansion upon freezing.

    4. Versatility as a solvent.

Cohesion and Adhesion

  • Cohesion: Hydrogen bonds hold water molecules together, aiding water transport against gravity in plants.

  • Adhesion: Attraction between different substances (e.g., water and plant cell walls).

Surface Tension

  • High surface tension due to hydrogen bonding makes it hard to break the liquid's surface.

Water's Temperature Moderation

  • Water absorbs heat from warmer air and releases heat to cooler air, changing its temperature slightly.

  • Thermal Energy and Temperature:

    • Kinetic energy relates to molecular motion; thermal energy associated with random motion is called thermal energy.

    • Caloric Measure:

    • Calorie is the heat needed to raise 1 g of water by 1°C.

    • Conversions:

      • 1 kcal = 1,000 cal; 1 J = 0.239 cal; 1 cal = 4.184 J.

Water’s High Specific Heat

  • Specific heat is the heat needed to change the temperature of 1 g by 1°C.

  • Water’s Specific Heat: 1 cal/g/°C

    • Water resists temperature changes due to its high specific heat, which is attributed to the breaking and forming of hydrogen bonds.

Evaporative Cooling

  • Evaporation: Transformation from liquid to gas; heat of vaporization is the heat necessary for this process.

  • Cooling Process: As liquid evaporates, the remaining surface cools, helping to stabilize temperatures in organisms.

Ice Formation and Density

  • Ice floats because hydrogen bonds create a more ordered arrangement, making it less dense than liquid water.

  • Water Density: Greatest at 4°C.

  • Impact of Sinking Ice: If ice sank, bodies of water would eventually freeze solid, threatening life.

Water as the Solvent of Life

  • A solution is a homogeneous mixture of substances; the solvent is the dissolving agent (water in this case).

  • Water’s polarity makes it a versatile solvent, surrounding ions with hydration shells when ionic compounds dissolve.

Hydrophilic and Hydrophobic Substances

  • Hydrophilic: Affinity for water.

  • Hydrophobic: Lacks affinity for water (e.g., oil).

  • Role in Cell Membranes: Hydrophobic molecules form major ingredients of cell membranes.

Concentration and Molarity

  • Molecular Mass: Total mass of a molecule's atoms.

  • Moles: 1 mole (mol) = 6.02 × 10²³ molecules.

  • Molarity: Number of moles of solute per liter of solution.

pH Scale and Acidity

  • Acids and Bases:

    • Acid increases H+ concentration; base reduces H+ concentration.

    • Strong acids/bases fully dissociate in water; weak acids/bases may reversibly release/accept H+.

  • pH Definition: pH = − log [H+].

  • Neutral Solutions: [H+] = 10⁻⁷.

Buffer Systems

  • Buffers: Substances that minimize changes in H+ and OH− concentrations.

    • Typically consist of a weak acid/base pair that can combine with H+ ions.

Ocean Acidification

  • Human activities (e.g., fossil fuel combustion) lead to CO2 absorption by oceans, forming carbonic acid.

  • Impact on Marine Life: Acidification threatens organisms requiring carbonate ions for calcification, such as corals.

Figures and Visuals

  • Reference various tables and figures illustrating molecular structures, water properties, and chemical balances in nature where applicable.

Note: The content includes scientific terminology and illustrations of environmental issues, emphasizing the essential nature of water in biological and ecological contexts.