Chapter 10 Kinetic Molecular Theory 10.2 & 10.3 Liquids and Solids

POINT > Describe liquids in terms of KMT POINT > Identify properties of liquids POINT > Describe solids in terms of KMT POINT > Identify properties of solids POINT > Describe different types of crystals and amorphous solids

POINT > Describe liquids in terms of KMT Particles in a liquid are in constant motion and have no fixed position relative to other particles As such, liquids are fluid (flow and take shape of container) Particles are much closer together than in gases As such, intermolecular forces are very significant and govern properties of liquids

1. High density relative to gases: Molecules are much closer together Densities of liquids can vary to a large degree 2. Relatively incompressible: Very little empty space between particles, in contrast to gases POINT > Identify properties of liquids

3. Liquids can diffuse into other liquids: Much slower than gases Rate of diffusion increases with temperature 4. Surface tension: Intermolecular forces drive reduction in surface area, especially with polar molecules Surface tension causes liquids to form spherical droplets (cohesion)

POINT > Identify properties of liquids 5. Capillary action: Liquids will be drawn into narrow tubes due to attraction between the liquid and the material of the tube (adhesion) 6. Evaporation: Particles with high kinetic energy escape attractive forces at the surface of a liquid

POINT > Identify properties of liquids Adhesion is the attraction between particles of different substances Cohesion is the attraction between particles of the same substance

WB CHECK: Compared to gases, liquids are a) more dense and compressible b) less dense and compressible c) less dense and incompressible d) more dense and incompressible

WB CHECK: Liquids and gases are similar in that they a) are both compressible b) are governed by intermolecular forces c) are fluids d) have surface tension

WB CHECK: A water drop sticks to a window due to a) cohesion b) adhesion c) capillary action d) evaporation

Particles in a solid are more closely packed than in liquids or gases As such, the attractive forces between particles have stronger effects Particles are in motion (vibration), but position is relatively fixed Solids do not flow or conform to container shape POINT > Describe solids in terms of KMT

POINT > Identify properties of solids 1. Definite shape and volume: Over a wide range of temperature or pressure, shape and volume are relatively stable 2. High density and incompressibility: Particles are closely packed together 3. Very slow diffusion: Diffusion between solids in contact will occur, but very slowly

POINT > Identify properties of solids 3. Very slow diffusion: Diffusion between solids in contact will occur, but very slowly

WB CHECK: What are 3 properties of solids?

POINT > Describe different types of crystals and amorphous solids Crystal solids are categorized into four groups: 1. Ionic crystals: Ions or polyatomic ions in a structured pattern Ex. NaCl hard and brittle, very high melting points 2. Covalent network crystals: All atoms covalently bound together Ex. diamond, quartz - usually very hard and brittle, very high melting points

POINT > Describe different types of crystals and amorphous solids 3. Metallic crystals: Metal cations in a “sea of electrons” high melting points, but less brittle (malleable, ductile) 4. Covalent molecular crystals: Covalent molecules held together by intermolecular forces. Softer than other crystals, much lower boiling points (why?) ex. Ice, sugar

POINT > Describe different types of crystals and amorphous solids Amorphous solids: No crystallization, so no real pattern in the structure. Properties vary widely Ex. plastics, glass

WB CHECK: Which of these is an ionic crystal? a)CH 4 b)lead c)MgBr 2 d)C 6 H 12 O 6

WB CHECK: Which of these would have the highest melting point? a)CH 4 b)H 2 O c)MgBr 2 d)glucose

Homework: Please read pages Questions #1-5 page 318 #1-5 page 323