Solid, Liquid, and Gas

Solid, Liquid, Gas (a) Particles in solid (b) Particles in liquid (c) Particles in gas

Solid H 2 O (s) Ice Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 31

Ice H 2 O (s) Ice Photograph of ice model Photograph of snowflakes Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Liquid H 2 O (l) Water Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 31 In a liquid molecules are in constant motion there are appreciable intermolecular forces molecules are close together Liquids are almost incompressible Liquids do not fill the container

Gas H 2 O (g) Steam Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 31

Liquids The two key properties we need to describe are EVAPORATIONCONDENSATION EVAPORATION and its opposite CONDENSATION add energy and break intermolecular bonds EVAPORATION release energy and form intermolecular bonds CONDENSATION

States of Matter

Gas, Liquid, and Solid Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 441 Gas Liquid Solid

States of Matter Solid Liquid Gas Holds Shape Fixed Volume Shape of Container Free Surface Fixed Volume Shape of Container Volume of Container heat

Some Properties of Solids, Liquids, and Gases Property Solid Liquid Gas Shape Has definite shapeTakes the shape of Takes the shape the container of its container Volume Has a definite volumeHas a definite volume Fills the volume of the container Arrangement of Fixed, very closeRandom, close Random, far apart Particles Interactions between Very strongStrong Essentially none particles

To evaporate, molecules must have sufficient energy to break IM forces. Molecules at the surface break away and become gas. Only those with enough KE escape. endothermicBreaking IM forces requires energy. The process of evaporation is endothermic. Evaporation is a cooling process. It requires heat. Evaporation

Change from gas to liquid Achieves a dynamic equilibrium with vaporization in a closed system. What is a closed system? A closed system means matter can’t go in or out. (put a cork in it) What the heck is a “dynamic equilibrium?” Condensation

When first sealed, the molecules gradually escape the surface of the liquid. As the molecules build up above the liquid - some condense back to a liquid. The rate at which the molecules evaporate and condense are equal. Dynamic Equilibrium

As time goes by the rate of vaporization remains constant but the rate of condensation increases because there are more molecules to condense. Equilibrium is reached when: Rate of Vaporization = Rate of Condensation Molecules are constantly changing phase “dynamic” The total amount of liquid and vapor remains constant “equilibrium” Dynamic Equilibrium

Relative Humidity (%) Outdoor Temperature ( o F) Double-glazed low-E, argon gas Double-glazed Single-glazed Triple-glazed 2 low-E coatings argon gas fill

Vaporization is an endothermic process - it requires heat. Energy is required to overcome intermolecular forces Responsible for cool earth Why we sweat Vaporization

Energy Changes Accompanying Phase Changes Solid Liquid Gas Melting Freezing Deposition CondensationVaporization Sublimation Energy of system Brown, LeMay, Bursten, Chemistry  2000, page 405