PP 17: Liquids & Solids
Drill: Draw 3 possible LDDs for:
C4H8O
Solids: (crystals): Any substance that has a well defined crystal structure
Molecular Solids: Covalently bound molecules held together by intermolecular forces (asphalt or ice)
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Non-conductors
Insoluble in water mostly
Low MP & BP
Held by intermolecular F
Intermolecular Forces: Instantaneous weak forces that hold one molecule to another or to
another part of itself
Importance of H-bonding: Hydrogen bonding will have a profound effect on the strength of the bond; thus,
will cause a tremendous increase of the BP or MP.
Network Molecular Solids or Macromolecules:
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Bound by a continuous network of covalent bonds
High MP, insoluble, non-conductor
Ionic Solids:
• Ions or ionic compounds held together by electrostatic charge
• Fattraction = Kq1q2/d2
• Non-conductors as solids
• Conductors in solution
• Soluble in water mostly
• Very high MP & BP
• Brittle
Metallic Solids:
• Conductors, insoluble in water mostly, high MP & BP, held by gravitational type force
• Fattraction = Gm1m2/d2
Crystal: Any substance or solid that has a well defined crystal structure
Crystal Lattice: The three dimensional arrangement of unit cells in a crystal structure
Unit Cell: The smallest repeating unit that a crystal structure can be divided into
Simple Cube: Unit cell with one atom at each vertex (1 atom per cell)
Body Centered Cube (BCC): Unit cell with one atom at each vertex & one atom in the center
of the cube (2 atoms per cell)
Face Centered Cube (FCC or CCP): Unit cell with one atom at each vertex & one atom on each
face of the cube (4 atoms per cell)
Great Website: http://departments.kings.edu/chemlab/animation/index.html
Hydrated Crystal: A solid with water in the crystal
(CuSO4*5H2O)
Anhydrous Solid: A crystal without water
Hygroscopic: Crystals that absorb moisture from the air
Deliquescent: Crystals that absorb enough moisture from the air to liquify
Efflorescent: Crystals that give up water to the surroundings
Polymorphous: When a single substance can have multiple crystal structures
Isomorphous: When different substances have the same crystal structure
Amorphous Solid: A solid w/o a well defined crystal structure
(Super-cooled liquid)
Liquid Crystals: Part solid & part liquid
• Has a well defined crystal structure in 1 or 2 but not all 3 dimensions
Solids: (crystals): Any substance that has a well defined crystal structure
• Definite size & shape
• Particles vibrate about fixed points
Liquid: Any substance that holds together loosely, but has no structure in any dimension
• Definite size but no shape
• Particles vibrate about moving points
Gas: Any substance that has no attraction among the particles
• No definite size or shape
• Particles move at random
Drill: Name & describe each of the 7 crystal structures
Melting Point (MP):
• Temperature at which the solid phase & liquid phase are at equilibrium
• MP & FP are equal
• Temperature at which the vapor pressure of a solid = the vapor pressure of its liquid phase
Boiling Point: Temperature at which the liquid phase & gaseous phase are at equilibrium
• Temperature at which the vapor pressure of a liquid = the vapor pressure of its
gaseous phase or atmospheric P
Adhesion: The attraction of particles from different substances to each other
Cohesion: The attraction of particles of the same substance towards each other
Capillarity: The movement of a liquid up a thin tube due to adhesion & cohesion
Surface Tension: Pressure on the surface of a liquid caused by the uneven forces acting
on the surface molecules
Vapor Pressure: The pressure caused by the evaporated particles in the vapor above a liquid
Intermolecular Forces: Weak short lasting forces between atoms from different molecules or
two different atoms on the same molecule. They occur over & over again.
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Hydrogen-bond
• Strongest of the intermolecular forces
• Occurs when H is bound to one highly EN element & connects to another
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Dipole-dipole
• When two polar molecules connect
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Dipole-induced dipole
• When a polar molecule gets near a non-polar one, it induces the non-polar
one to become polar; thus, they connect
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London dispersion forces
• Instantaneous attraction for fractions of seconds in which non-polar molecules connect
• Very weak force
Predict & explain the MP trends of:
1) Li, Na, K, & Rb
2) F2, Cl2, Br2, & I2
3) LiF, NaCl, KBr, & RbI
Phase Diagram: Graphic representation of all the phases of a substance with respect to temperature & pressure