Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION Chapter 10 Liquids and Solids

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Forces between (rather than within) molecules. CHANGES in STATES: –Due to changes in the intermolecular forces between the molecules –Rather than the forces within the molecules. Section 10-1

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 Figure 10.1 Schematic Representations of the Three States of Matter

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 INDIVIDUAL MOLECULES FAR APART PARTICLES INTERACTING VERY LITTLE

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 MOLECULES ARE VIRTUALLY LOCKED IN PLACE CAN VIBRATE ABOUT THEIR POSITIONS VERY ORGANIZED

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 MOTION OF MOLECULES IS INCREASE GREATER MOVEMENT GREATER DISORDER

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 DIPOLE-DIPOLE FORCES FORCES THAT ACT BETWEEN POLAR MOLECULES RESULT WHEN THE PARTIAL POSITIVE AND NEGATIVE CHARGES OF NEIGHBORING MOLECULES ATTRACT

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8  dipole-dipole attraction: molecules with dipoles orient themselves so that “+” and “  ” ends of the dipoles are close to each other. Ô

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 Figure 10.2

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 Ô Special type of Dipole-Dipole Ô hydrogen bonds: dipole-dipole attraction in which hydrogen is bound to a highly electronegative atom. (F, O, N)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 DIPOLE-DIPOLE FORCES Only important at close distances Unimportant in gases where molecules are far apart.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 HYDROGEN BONDING TYPE OF DIPOLE-DIPOLE FORCE UNUSUALLY STRONG FOUND IN MOLECULES WHERE HYDROGEN IS BOUND TO A HIGHLY ELECTRONEGATIVE ATOM SUCH AS OXYGEN, NITROGEN, OR FLUORINE

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 REASONS FOR HYDROGEN BONDING UNUSUALLY STRONG BONDING due to –Great polarity of the X – H bond. –Very small size of H atom and 1 st element of each group which allows for the close approach of the dipoles.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 Figure 10.3 A Water Molecule

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 Hydrogen- Bonding Important effect on physical properties Example, boiling points of covalent hydrides of Group 4A, 5A, 6A & 7A Generally, bp  as Molar mass 

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 Figure 10.4 The Boiling Points of the Covalent Hydrides of the Elements in Groups 4A, 5A, 6A, and 7A  Very High bp due to H-bonding in the liquid state.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 LONDON DISPERSION FORCES FORCES THAT EXIST AMONG NOBLE GAS ATOMS AND NON-POLAR MOLECULES IMPORTANT FOR MOLECULES WITHOUT DIPOLE MOMENTS RESULTS FROM THE CONSTANT MOTION OF ELECTRONS WHICH RESULTS IN THE FORMATION OF INSTANTANEOUS DIPOLES WEAK/ SHORT-LIVED ATTRACTION

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 Figure 10.5 London Dispersion Forces

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 London Dispersion Forces 4 relatively weak forces that exist among noble gas atoms and nonpolar molecules. (Ar, C 8 H 18 ) 4 caused by instantaneous dipole, in which electron distribution becomes asymmetrical. 4 the ease with which electron “cloud” of an atom can be distorted is called polarizability.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 London Dispersion Forces Increase greatly as size of atom increases. The larger the atom, the easier for the electron cloud to become distorted. Table 10.2

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21 QUESTION? PUT THE FOLLOWING SUBSTANCES IN ORDER FROM LOWEST TO HIGHEST BOILING POINT. C 2 H 6 NH 3 F 2

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22 ANSWER –LOWEST : F 2 ONLY HAS LONDON DISPERSION FORCES -- NEXT: C 2 H 6 NOT ESPECIALLY POLAR, BUT SLIGHTLY -- HIGHEST: NH 3 HYDROGEN BONDING FORCES Don’t forget your Homework Exercises

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 Section 10.2 THE LIQUID STATE - LOW COMPRESSIBILITY - LACK OF RIGIDITY - HIGH DENSITY COMPARED TO GASES -TEND TO BEAD AS DROPLETS ON SOLID SURFACES

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 Some Properties of a Liquid Surface Tension: The resistance to an increase in its surface area (polar molecules). Capillary Action: Spontaneous rising of a liquid in a narrow tube. Viscosity: Resistance to flow (molecules with large intermolecular forces).

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25 Figure 10.6 Molecules in a Liquid

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 Surface Tension UNEVEN PULL OF MOLECULES AT THE SURFACE CAUSES LIQUID TO FORM SHAPE OF MINIMUM SURFACE AREA  SPHERE

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 27 SURFACE TENSION Resistance of a liquid to increase its surface area. Liquids with strong intermolecular forces have high surface tension.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 28 CAPILLARY ACTION Spontaneous rising of a liquid in a narrow tube.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 BALANCE OF TWO FORCES (1)COHESIVE FORCES: INTERMOLECULAR FORCES OF LIQUIDS (i.e., FORCES BETWEEN MOLECULES OF LIQUID) (2) ADHESIVE FORCES: FORCES BETWEEN LIQUID MOLECULES AND THE WALLS OF THE CONTAINER

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 See Figure 10.7 Page Depends on the substance the container or surface is made of.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 31 VISCOSITY -- Measure of a liquids resistance to flow. -- Measured as the time it takes a steel ball to fall through the liquid. -- Strongly dependent on intermolecular forces.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 32 = VISCOSITY -- LIQUIDS WITH LARGE INTERMOLECULAR FORCES HAVE HIGH VISCOSITY -- VERY LARGE MOLECULES CAN HAVE HIGH VISCOSITY SINCE THESE MOLECULES CAN ENTANGLE Homework: Don’t forget!!