PHASE TRANSITION

• Where is phase change used?


  • Conditioning of buildings, such as 'ice-storage'
  • Cooling of heat and electrical engines
  • Cooling: food, beverages, coffee, wine, milk products, green houses
  • Medical applications: transportation of blood, operating tables, hot-cold therapies
  • Waste heat recovery
  • Solar power plants
  • Spacecraft thermal systems
  • Thermal comfort in vehicles
  • Thermal protection of electronic devices
  • Thermal protection of food: transport, hotel trade, ice-cream, etc.
  • Textiles used in clothing
  • Computer cooling
• Review: 3 Phases of Matter

  • Solid
  • Liquid
  • Gas

  
• Phase change


  Heat energy is either absorbed or released

  
• Heat energy release


  Molecules slow down and move closer together

  
• Heat energy absorption


  Molecules speed up and expand

  
• Types of Phase Changes

  • Melting
  • Freezing
  • Vaporization (Boiling)
  • Evaporation
  • Condensation
  • Sublimation
  • Deposition

  
• Melting


  Phase change from a solid to a liquid, molecules speed up, move farther apart, and absorb heat energy

  
• Freezing


  Phase change from a liquid to a solid, molecules slow down, move closer together and release heat energy

  
• Vaporization (Boiling)


  Phase change from a liquid to gas, occurs at the boiling point, molecules speed up, move farther apart, and absorb heat energy

  
• Evaporation


  Phase change from a liquid to a gas on the surface of a liquid (occurs at all temperatures), molecules speed up, move farther apart, and absorb heat energy

  
• Condensation


  Phase change from a gas to a liquid, molecules slow down, move closer together and release heat energy

  
• Sublimation


  Phase change from a solid to a gas, molecules speed up, move farther apart, and absorb heat energy

  
• Deposition


  Phase change from a gas to a solid, molecules slow down, move closer together and release heat energy

  
• Melting Point


  The temperature at which a solid changes into a liquid

  
• Boiling Point


  The temperature at which a liquid changes into a gas
• Levels of Organization


  • Atoms
  • Molecules
  • Macromolecules
• There are four macromolecules that are essential for life to exist
• The four biomolecules


  • Carbohydrates
  • Lipids
  • Nucleic Acids
  • Proteins
• Phase Transition


  From Simple to Advance Perspective
• We typically get biomolecules from food... this is why we must eat in the first place!
• Contents


  • Phases of matter
  • Review of phase changes
  • Biomolecules
  • Biomolecules' Self-Assembly
  • Importance of Self-Assembly
• The biomolecules serve to keep organisms alive
• Carbohydrates


  Are sugars! We get 4 kilocalories per gram of carb that we eat!
• Carbohydrates


  Most common organic molecule, function is primary energy source our body needs, elements present are C, H, O (1:2:1 ratio)
• Carbohydrate monomers and polymers

  • Monosaccharides (Glucose is most common)
  • Disaccharides
  • Polysaccharides (starch, Glycogen, Cellulose, Chitin)
• Self-Assembly


  A reversible process that involves pre-existing, distinct components of an initially disordered structure
• Carbohydrate sources


  • Chocolate, Bread, Pasta, Fruits, Vegetables (ALL FROM PLANTS!!!)
• Self-Assembly ≠ formation
• Types of sugars


  • Monosaccharide (single sugar, e.g. glucose, fructose)
  • Disaccharide (2 monosaccharides, e.g. maltose, sucrose)
  • Polysaccharide (3+ monosaccharides, e.g. Starch, Glycogen, Cellulose, Chitin)
• Self-Assembly


  • Has origins in organic chemistry: structures are determined bond-by-bond, but the structures are molecules (less than about 0.5 nm in size)
  • It is impossible to direct the formation (bond-by-bond) of larger nano- and micro-scale structures
  • Self-assembly fills the processing gap by utilizing specific (usually weak) interactions between molecules to build 2-D and 3-D structures in the 10's to 100's nm size range
• Starch


  Used for energy storage in plants, found in potatoes, pasta and rice, provides a quick form of energy for the body
• Many things (living and non-living) spontaneously organize over many length scales: Å to light year
• Glycogen


  Used for energy storage in animals, formed in the Liver
• Cellulose


  Provides structural support in plants (found in the cell wall)
• Chitin


  Found in exoskeletons of arthropods (insects, spiders), found in cell wall of some fungi
• Structure of carbohydrates: primarily in a ring shape (but not always), elements are C, H, and O
• Forces at Work in self assembly

  • van der Waals
  • Brownian Motion
  • Gravitation
  • Electrostatics
  • Capillary Forces
  • Electromagnetic Fields
  • Hydrogen Bonds
  • Entropic Interactions
  • Magnetic Interactions
  • Coordination Bonds
• Lipids


  Are fats, we get 9 kcals per gram of fat that we consume, function is to store energy, insulate the body, and make up the cell membrane
• Self-assembly


  • Usually occurs in a fluid-like state. The materials (molecules or particles) should be able to move around. They sample many different orientations and interactions with respect to each other. One orientation (interaction) tends to be more favorable than others. Given enough time, the structural elements optimize their local environments to produce a self-organized structure over a large volume
• Lipids


  Elements are C-H-O, monomers are glycerol & 3 fatty acids, polymers are phospholipids, triglycerides