Lesson 1: Structure of water and hydrogen bonding

• cytosol - the water-based “goo” inside the cell wherein most of an organism’s cellular chemistry and metabolism occur
• Life-sustaining properties of water:

  • Polar
  • Universal solvent
  • High specific heat capacity
  • High heat of vaporization
  • Cohesion and adhesion
  • Less dense as solid than liquid
• hydrogen bonding -  weak interactions that form between a hydrogen with a partial positive charge and a more electronegative atom
• hydrophilic - a charged or polar substance that interacts with and dissolves in water
• hydrophobic - nonpolar molecules like oils and fats do not interact well with water and they separate from it rather than dissolve in it
• cohesion - attraction of molecules for other molecules of the same kind
• • cohesion; surface tension
  • adhesion; capillary action
• surface tension - tendency of a liquid’s surface to resist rupture when placed under tension or stress
• adhesion - attraction of molecules of one kind for molecules of a different kind
• capillary action - upward motion against gravity through thin glass tubes
• capillary action, depends on the attraction between water molecules and the glass walls of the tube (adhesion), as well as on interactions between water molecules (cohesion)
• What is the curved surface formed by a liquid in a cylinder or tube?

  capillary action

  A) meniscus

  
• In liquid water, hydrogen bonds are constantly formed and broken as the water molecules slide past each other. The breaking of these bonds is caused by the kinetic energy of the water molecules due to the heat contained in the system.
• When the temperature drops and water freezes, water molecules form a crystal structure maintained by hydrogen bonding (as there is too little heat energy left to break the hydrogen bonds), forming a solid structure called ice
• When the heat is raised (for instance, as water is boiled), the higher kinetic energy of the water molecules causes the hydrogen bonds to break completely and allows water molecules to escape into the air as gas
• Water’s lower density in its solid form than liquid
• Water has a high specific heat capacity - the amount of heat needed to raise the temperature of 1g of a substance by 1 °C
• calorie - the amount of heat/energy needed to raise the temperature of 1g of water by 1 degree
• Water’s heat of vaporization is around 540 cal/g at 100 °C, water's boiling point.
• Water has a high heat of vaporization - the energy needed to change a substance from a liquid to a gas at constant temperature
• A water molecule consists of two hydrogen atoms bonded to an oxygen atom, and its overall structure is bent
• evaporative cooling - the process in which as water molecules evaporate, the surface they evaporate from gets cooler
• kinetic energy; energy of motion; heat
• polar molecule - a neutral, or uncharged molecule that has an asymmetric internal distribution of charge, leading to partially positive and partially negative regions
• density - mass per unit volume of a substance, measured in kg/m3
• Water molecules are polar, with partial positive charges on the hydrogens, a partial negative charge on the oxygen
• Water has the unique ability to dissolve many polar and ionic substances, but cannot dissolve nonpolar molecules like oils which lack partial positive or partial negative charges, so they are not attracted to water molecules
• Identify the missing words corresponding to the image below

  A) concave

  B) adhesion

  C) convex

  D) cohesion

  
• Identify the types of bonding in the image below

  A) polar covalent bond

  B) hydrogen bond

  
• capillary action - movement of water within spaces of the lattice of a porous material due to its attraction to the substance itself, forming adhesion, cohesion, and surface tension
• Water is an anomaly in its lower density as solid, caused by expansion
• biology - a study of life and the science of living organisms including their structure, composition, function, and development
• Characteristics of Life:

  • Growth and development
  • Reproduce offspring
  • Heredity of traits
  • Homeostasis
  • Metabolism
  • Cellular structure and composition
  • Respond to the environment
• homeostasis - the maintenance of a constant internal environment despite changes in the external environment; stable inner conditions
• metabolism - the sum of all the chemical reactions in a cell or organism