Heating Curve evruC gnitaeH

Explain the plateau of heating and cooling curves. Include: IMFs, exothermic, endothermic Define melting and boiling point in terms of intermolecular forces and particle size. Additional KEY Terms

Heating Plateau: Minimum amount of energy is needed to overcome the intermolecular forces – endothermic process. All added heat is used to overcome these forces, NOT increase kinetic energy (temperature). Plateau ends when all particles have phase changed.

Cooling Plateau: Particles lose energy and slow down - pulled together by the IMFs. Organizing into restrictive phases causes the release of stored energy – exothermic process Freezing of Water Freezing Point Plateau ends when all particles have phase changed.

Freezing of Water Freezing Point

Melting and boiling points are a characteristic physical property. Generally, as mass increases, melting/boiling point also increases. (more intermolecular forces to work against)

Ionic compounds typically have higher melting point than molecular compounds. NaCl Sugar 160 o C 801 o C

IMFs must be overcome in order for a substance to change states/phases. The greater the forces between the particles, the more energy needed to overcome these forces. H O H Cl - Na + H O H Cl - Na + So, the greater the IMFs, the higher the melting and boiling point.

CAN YOU / HAVE YOU? Explain the plateau of heating and cooling curves. Include: IMFs, exothermic, endothermic Define melting and boiling point in terms of intermolecular forces and particle size. Additional KEY Terms