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Chapter 11.1-11.9 Liquids, Solids, and Intermolecular Forces
● Properties of matter are determined by the properties of molecules and atoms
11.1 Water, No Gravity:
● Intermolecular forces - Attractive forces that exist among the particles that compose
matter. The molecules attract other water molecules.
● Intermolecular forces exist among all particles that compose matter.
● The state of matter ( gas, solid, liquid) depends on the magnitude of the intermolecular
forces along with the amount of thermal energy.
● Molecules composing matter are in constant random motion that are increased with the
amount of thermal energy.
● Increasing thermal energy with intermolecular forces = gaseous; Decreasing thermal
energy with intermolecular forces = liquid or solid
11.2 Solids, Liquids, and Gases: A Molecular Comparison
● Densities of solids and liquids are much greater than gases
● For water, solids are slightly less dense than liquids. This is atypical behavior because
molecules move closer upon freezing (solids).
● Ice however is a unique solid that is less dense than water because the unique crystal
structure results in water molecules moving slightly apart upon freezing.
● Molecules closely spaced (solids and liquids) are not easily compressed, while
molecules widely spaced (gases) are highly compressible.
● Solids can be crystalline - atoms are arranged in a well ordered 3D array - or amorphous
- atoms have no long range order.
● Changed between states can be achieved by changing temperature and/or pressure.
High pressure = denser (solids). Lower pressure = less dense (gases)
11.3 Intermolecular Forces: The Forces that hold Condensed States Together
● The structure that composes a substance determines the strength of the intermolecular
forces that hold the substance together which then determines the state of the
● At room temperature
○ Solids and Liquids → Moderate to strong intermolecular forces (High Melting &
○ Gases → Weak intermolecular forces (Low Melting & Boiling Points)
● Intermolecular forces originate from interactions among charges, partial charges, and
● Protons and electrons are attracted to one another because their potential energy
decreases as they get closer.
● Intermolecular forces are much weaker than bonding forces.
● Bonding forces are large charges at close distance.
● Intermolecular forces are small charges acting at great distances.
● To break O-H bonds in water (1000 degrees Celsius) but to break the intermolecular
cond (100 degrees Celsius) ← boiling point.
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