Phase Changes “It’s just a phase”

States of Matter States - Solid, Liquid, and Gases Phase changes are caused by a change of heat or pressure. More often heat. HEAT and TEMPERATURE are not the same thing.

Temperature Measures the average kinetic energy of the particles in a substance. Kinetic energy is how fast the molecules are moving (heat). The faster the particles/molecules are moving the higher the temperature.

Solids Molecules are tightly packed together. Strong intermolecular forces. Particles vibrate in place.

Liquids Particles are less tightly packed (liquids flow and can be poured). Weaker intermolecular forces. Surface Tension-ability of a liquid’s molecules to “stick” together.

Gases Particles spread out in container. High kinetic energy, particles are moving very quickly. Kinetic Energy: Energy of motion Very weak intermolecular forces.

Where does all the energy go? During a phase change energy is added, but the temperature does not increase. The energy goes toward breaking up weak intermolecular forces between the particles.

Intermolecular Forces Interactions between particles that cause them to “stick” together. Strongest in solids Weakest in gases Strongest when particles move slowly. During phase changes, IMF’s are either weakened/broken or strengthened/bonded.

Phase Change Diagrams