Some Properties of a Liquid Surface Tension: The resistance to an increase in its surface area (polar molecules, liquid metals). Strong intermolecular forces High surface tension =

IAN BUG Surface of water behaving like it had an “elastic skin”

attracted to each other Capillary Action: Spontaneous rising of a liquid in a narrow tube. Cohesion is the intermolecular attraction between like molecules Adhesion Cohesion Adhesion is an attraction between unlike molecules attracted to glass attracted to each other

Some Properties of a Liquid Viscosity: Resistance to flow High viscosity is an indication of strong intermolecular forces

General Classification of Solids Crystalline Solids: Well-ordered, definite arrangement of atoms. (Examples- metals, H2O, diamond) Amorphous: No pattern to the arrangement of particles. (Examples- glass, plastic, wax)

Representation of Components in a Crystalline Solid Lattice: A 3-dimensional system of points designating the centers of components (atoms, ions, or molecules) that make up the substance.

Which of the following consistently have the highest melting points? Metals Salts Molecular crystals Alkanes Hydrogen-bonded compounds. Answer: B

How sharp are you? Gases can be compressed more easily than liquids because: Gas molecules are smaller than liquid molecules B. The kinetic energy of gas molecules is higher than that found in liquids The average intermolecular distances are greater in gases than those found in liquids. Intermolecular forces increase as gas moleculues are brought closer together. E. None of the above. Answer: C In a gas, the molecules are separated by a large distance and are able to be compressed by increasing the pressure. They move independently of one another because there is no appreciable intermolecular interactions among them.

In which of the following are the intermolecular forces listed from the weakest to the strongest? Dipole-dipole>London>hydrogen bonds London<dipole-dipole<hydrogen bonds Hydrogen bonds<dipole-dipole<London London>hydrogen bonds>dipole-dipole London>Akbar bonds>dipole-dipole>Basu forces Answer: B

Which of the following compounds will NOT hydrogen- bond>? CF4 CH3OH H2NCH2CH2CH3 HOCH2CH2OH HClO Answer: A

Water has a higher capillary action than mercury due to: Higher dipole-dipole forces between the water molecules Strong cohesive forces within water. Very significant induced intermolecular attractions. Weak adhesive forces in water Strong cohesive forces in water which work with strong adhesive forces. Answer: E. The strong adhesive forces leads to a creeping effect as water moves up the narrow tubing and the strong cohesive forces attempt to minimize the surface area.

Small drops of water tend to bead up because of: High capillary action the shape of the meniscus The resistance to increased surface area. Low London dispersion forces Weak covalent bonds. Answer: C. This is a description of surface tension, which is a result of high dipole-dipole forces between water molecules. These intermolecular forces are also called…..hydrogen bonds!

Several liquids are compared by adding them to a series of 50 mL graduated cylinders, then dropping a steel ball of uniform size and mass into each. The time required for the ball to reach the bottom of the cylinder is noted. This is a method used to compare the differences in a property of liquids known as: Surface tension Buoyancy Capillary action Viscosity Surface contraction Answer: D. The resistance to flow of any fluid is called viscosity. As You would predict, liquids with high viscosity (ex: maple syrup) have large intermolecular forces.

Types of Crystalline Solids There are four types of crystalline solid: - Molecular (formed from atoms or molecules) - usually soft with low melting points and poor conductivity. - Covalent network (formed from atoms) - very hard with very high melting points and poor conductivity. - Ionic (formed form ions) - hard, brittle, high melting points and poor conductivity. - Metallic (formed from metal atoms) - soft or hard, high melting points, good conductivity, malleable and ductile.

Bonding in Crystalline Solids Know these!! Metallic bonds are formed from metal nuclei floating in a sea of electrons.

Crystalline Solids Molecular Covalent Network Ionic Metallic

Metal Alloys Substitutional Alloy: some metal atoms replaced by others of similar size. brass = Cu/Zn

Metal Alloys (continued) Interstitial Alloy: Interstices (holes) in closest packed metal structure are occupied by small atoms. steel = iron + carbon

Please complete the following problems: Pg. 475-82 #12, 20, 30, 32, 34, 36 (a,b and d) and 110

Phase Changes & Energy Endothermic: melting, evaporating/boiling & sublimation Exothermic: freezing, condensation, & deposition

Phase Changes & Energy heat of vaporization: the heat energy required to evaporate a given mass of liquid at a constant temperature heat of fusion: the heat energy required to melt a given mass of solid at a constant temperature The temperature, (average KE), during a phase change (such as boiling) does not change! Any heat added during boiling gives more molecules enough energy to escape the liquid. Heating Curve

Phase Changes & Energy Generally, it will take more heat to vaporize a liquid than to melt a solid… (∆H(vap) > ∆H(fusion) ) Why? Every intermolecular bond is broken when vaporizing, but only some of the intermolecular forces break when melting solids. ?

Practice Time: Please attempt the following problems (at your workstations!): pg. 478-80: 88 and 90. To be collected by end of block. OR?

Do Now: Please pick up a copy of today’s assignment and complete it INDEPENDENTLY! Objective: Describe vapor pressurechanges in state, and phase diagrams. HW: Complete problem set handout. 120516

Gases can be liquefied by: increasing pressure at some temperature. Liquefying Gases Gases can be liquefied by: increasing pressure at some temperature. decreasing the temperature at some pressure. - Critical temperature: the highest temperature at which a substance can remain a liquid regardless of the pressure applied. - Critical pressure: the pressure needed at the critical temperature.

Phase Diagrams Shows the relationship between the 3 phases of matter at various temperatures and pressures. Triple Point: All 3 phases of matter at equilibrium. Critical Point: The highest temperature at which the liquid phase can exist.

Phase Diagrams of H2O and CO2 Notice the slope of the solid–liquid equilibrium line.