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Changes of state, bonding and temperatures

Bonding, structure and the properties of matter • Bonding and substance properties

Key concepts

What you'll likely be quizzed about

  • Heating adds energy to a substance, increasing the kinetic energy of particles and providing energy to overcome attractive forces.
  • During melting and boiling, temperature stays constant while energy is absorbed to break attractions; this energy is termed latent heat.
  • Cooling decreases particle energy and allows attractions to form, resulting in solidification or condensation at a constant temperature until the phase change is complete.

Flashcards

Test your knowledge with interactive flashcards

Pressure effect on boiling point

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Increasing external pressure raises the boiling point since more energy is required for molecules to transition to the gas phase; decreasing pressure lowers the boiling point.

Key notes

Important points to keep in mind

Melting and boiling points denote strength of particle attractions, not just kinetic energy.

Phase changes utilize latent heat; temperature remains constant during these changes.

Ionic, metallic, and covalent network solids exhibit high melting and boiling points due to robust bonding.

Simple molecular substances possess low melting and boiling points because of weak intermolecular forces.

Predict state by correlating ambient temperature with melting and boiling points at the relevant pressure.

Pressure changes alter boiling point, with standard data assuming normal atmospheric pressure.

Intermolecular forces dictate bulk properties of molecular substances while covalent bonds stay intact.

Utilize Q = mL for energy calculations of phase changes, applying the accurate latent heat value for each substance.

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