RMBB_C2 BeCsLi 2010 IV. Phase Change -Occurs as a result of addition or removal of heat; also involves breaking of IMF

RMBB_C2 BeCsLi 2010 Phase Changes

RMBB_C2 BeCsLi 2010 Heating Curve

RMBB_C2 BeCsLi 2010 Phase Diagram - a graphical way to summarize the conditions under which equilibrium exist between the different states of matter. It allows us to predict the phase of a substance that is stable at any given temperature and pressure

RMBB_C2 BeCsLi 2010 Triple Point: where all three phases are in equilibrium Critical Point: point where critical Temp. and Pressure is achieved Critical Temperature: highest temperature at which a distinct liquid phase can form Critical Pressure: pressure required to bring about liquefaction at critical temperature Boiling point : temp. at which the vapor pressure of a liquid equals the atmospheric pressure.  IMF strength,  B. Pt. ( normal B.Pt.: B. Pt. at 1 atm) Melting point : temp. at which liquid and solid phase coexists in equilibrium. Under same pressure, solids with  IMF strength have  M. Pt. TERMS

RMBB_C2 BeCsLi 2010 V. Properties of liquid - Liquids are almost incompressible, assume the shape but not the volume of container: - Liquids molecules are held closer together than gas molecules, but not so rigidly that the molecules cannot slide past each other. 1.Viscosity – liquid’s resistance to flow due to IMF which impedes movement - increase in surface area of the molecule results to increase in viscosity. Explain why. - increase in temperature results to decrease in viscosity. Why? What is the relationship of Viscosity and IMF?

RMBB_C2 BeCsLi 2010

RMBB_C2 BeCsLi Surface Tension - amount of energy required to increase the surface area of a liquid - measure of the “cohesive force that must be overcome” Liquid surface tends to have the smallest possible area What is the relationship of Surface Tension and IMF? Compare water, mercury and ethanol in terms of S.T.

RMBB_C2 BeCsLi Capillarity/ Capillary Action– rising of a liquid through a narrow space against the pull of gravity Cohesive Force – binds molecules to each other (IMF) Adhesive Force – binds molecules to a surface Meniscus - the shape of the liquid surface. adhesive forces > cohesive forces the liquid surface is attracted to its container more than the bulk molecules. Therefore, the meniscus is U- shaped (e.g. water in glass). cohesive forces > adhesive forces the meniscus is curved downwards