Chapter 11 sec 1

States and state change

States of MatterThe fundamental difference between states of matter is the distance between particles.

States of MatterGases – fill container, random rapid motion, never coming to rest or clumping togetherMotion is mainly translational

Liquids – fixed volume, flow and assume shape of container, only slightly compressible, stronger forces hold molecules togetherMotion is mainly translational

EOS

Solids – fixed volume, definite shape, generally less compressible than liquids, forces hold particles in a fixed shapeMotion is mainly vibrational

Solid particles have fixed position

Crystalline form: they can be very hard and brittle or they can be very soft.

Liquid particles can move easily past one another

Liquid flow to take the shape of the lower part of a container.

EOS

Capillary action results from intermolecular interactions

A meniscus is the interface between a liquid and the air above it

Surface TensionSurface tension () is the amount of work required to extend a liquid surface and is usually expressed in unit of J m–2

EOS

Adhesive forces are intermolecular forces between unlike moleculesCohesive forces are intermolecular forces between like molecules

Vaporization and Condensation

Vaporization is the conversion of a liquid to a gas.

EOS

Condensation is the change of a gas to a liquid.

The boiling point of a liquid is the temperature at which its vapor pressure becomes equal to the external pressure

Phase Changes Involving Solids

The conversion of a solid to a liquid is called melting, or fusion, and the temperature at which a solid melts is its melting point

Sublimation is the process of a molecule’s passing directly from the solid to the vapor state

A phase diagram is a graphical representation of the temperature and pressure conditions under which a substance exists as a solid, liquid, gas, or some combination of these in equilibrium

Phase Diagrams

fusion curve

triple point

EOS

critical point

vapor pressure curve

sublimation curve

Practice

• A sample of water has a fixed volume and shape. What state is it in?

• What property of a liquid enable you to pour a liquid into a cup until the top of the liquid is slightly higher than the top of the cup?

• During what process does a liquid change to solid?

solid

Surface tension

freezing