Chemistry Chapter 10: Liquids and Solids PDF

Cover Page Chapter 10 Liquids and Solids Copyright ©2017 Cengage Learning. All Rights Reserved. Chapter 10 Table of Contents Table of Contents  (10.1...

Cover Page Chapter 10 Liquids and Solids Copyright ©2017 Cengage Learning. All Rights Reserved. Chapter 10 Table of Contents Table of Contents  (10.1) Intermolecular forces  (10.2) The liquid state  (10.3) An introduction to structures and types of solids  (10.4) Structure and bonding in metals Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Intramolecular Bonding Atoms can form stable units called molecules by sharing electrons. This is called intramolecular bonding. Intramolecular bonding “Within” the molecule. * Molecules are formed by sharing electrons between the atoms. Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Intramolecular and Intermolecular Bonding  Intramolecular bonding - Occurs within molecules  Condensed states of matter - Liquids and solids  Forces involved  Covalent bonding  Ionic bonding Copyright ©2017 Cengage Learning. All Rights Reserved. Copyright © Cengage Learning. All rights reserved 4 Section 10.1 Intermolecular Forces Intermolecular Forces  Forces that occur between molecules.  * Dipole-Dipole forces  * Hydrogen bonding  * London dispersion forces  Intramolecular bonds are stronger than intermolecular forces Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Hydrogen Bonding in Water  Blue dotted lines are the intermolecular forces between the water molecules. Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Changes in States  When a substance changes from solid to liquid to gas, the molecules remain intact  Caused by the changes in the forces among the molecules and not within the molecules  When energy is added to ice, the motion of the molecules increases  Results in greater movement and disorder Copyright ©2017 Cengage Learning. All Rights Reserved. characteristic of liquid water Section 10.1 Intermolecular Forces Figure - Schematic Representations of the Three States of Matter Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Phase Changes  Solid to Liquid  As energy is added, the motions of the molecules increase, and they eventually achieve the greater movement and disorder characteristic of a liquid.  Liquid to Gas  As more energy is added, the gaseous state is eventually reached, with the individual molecules far apart and Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Densities of the Three States of Water Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Dipole-Dipole Forces  Dipole moment – molecules with polar bonds often behave in an electric field as if they had a center of positive charge and a center of negative charge.  Molecules with dipole moments can attract each other electrostatically. They line up so that the positive and negative ends are close to each other.  Only about 1% as strong as covalent or ionic bonds. Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Characteristics of Dipole–Dipole Forces  Approximately 1% as strong as covalent or ionic bonds  Strength of the forces decreases as the distance between the dipoles increases Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Hydrogen Bonding  Strong dipole-dipole forces.  Hydrogen is bound to a highly electronegative atom – nitrogen, oxygen, or fluorine. Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Figure - Hydrogen Bonding in Water Hydrogen bonding among water molecules The polar water Note that the small size of the hydrogen molecule atom allows for close interactions Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces London Dispersion Forces  Forces that exist among noble gas atoms and nonpolar molecules  An accidental instantaneous dipole that occurs in an atom can induce a similar dipole in a neighbouring atom  Leads to an interatomic attraction that is weak and short-lived  Can be significant for large atoms Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces London Dispersion Forces (Continued)  Polarizability - Indicates the ease with which the electron cloud of an atom can be distorted to give a dipolar charge distribution  As the atomic number increases, the number of electrons increases  Increases the probability of the occurrence of momentary dipole interactions  Used by nonpolar molecules to attract each other Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Melting and Boiling Points  In general, the stronger the intermolecular forces, the higher the melting and boiling points. Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Concept Check Which molecule is capable of forming stronger intermolecular forces? N2 H2O Explain. Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Concept Check Draw two Lewis structures for the formula C2H6O and compare the boiling points of the two molecules. H H H H H C C O H H C O C H H H H H Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Chemical and Physical Changes at the Macroscopic Level Physical change Change in the form of the substance, but not in its chemical composition Chemical change Change of substances into other substances with different properties and different composition Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Distinguishing Chemical and Physical Changes  Aided by a molecular-level perspective  Example of a physical change  Phase change - Boiling of water  Energy as heat is transferred to liquid water  Intermolecular forces (hydrogen bonding) are overcome, and water vapor is formed as a result H 2 O l    H 2O  g  Copyright ©2017 Cengage Learning. All Rights Reserved. Chapter 10 Table of Contents Distinguishing Chemical and Physical Changes… Continue  Notice that the molecules do not change, that is: at the beginning and end of the physical change, the chemical composition of H2O is the same.  However, the molecules are held together by hydrogen bonding in the liquid but not in the vapor.  So the change of water from the liquid to the gaseous phase is a physical process because the H2O molecules remain intact during the Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Distinguishing Chemical and Physical Changes (continued)  If a process results by breaking and/or forming chemical bonds (intramolecular forces), the process is chemical change.  Example of a chemical change  Combustion of methane (CH4) to form CO2 and H2OCH 4 + 2O 2   CO 2 + 2H 2O  Chemical bonds between C and H in CH4 and between O atoms in O2 must be broken:  ChemicalCopyright bonds between C and O in CO2 and H ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Example-1  Which one of the following is the strongest intermolecular force experienced by noble gases? a. London dispersion forces b. Dipole–dipole attraction c. Hydrogen bonding d. Ion–ion interactions Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Example-2  Which of the following species exhibits the strongest intermolecular forces? a. CH4 b. H2O c. N2 d. CO e. He Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Example-3  When a water molecule forms a hydrogen bond with another water molecule, which atoms are involved in the interaction? a. A hydrogen atom from one water molecule and a hydrogen atom from the other water molecule b. An oxygen atom from one water molecule and an oxygen atom from the other water moleculeCopyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Example-3 (continued) c. A hydrogen atom from one water molecule and an oxygen atom from the other water molecule d. Two hydrogen atoms from one water molecule and one hydrogen atom from the other water molecule e. A hydrogen atom and an oxygen atom from the same water molecule Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.1 Intermolecular Forces Example-4  What type(s) of intermolecular forces is (are) exhibited by methane (CH4)? a. Hydrogen bonding and London dispersion forces b. Hydrogen bonding c. Dipole–dipole and London dispersion forces d. London dispersion forces Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.2 The Liquid State Liquid  Liquid and liquid solutions are vital to our lives. Of course, water is the most important liquid. Besides being essential to life, water provides a medium for food preparation, for transportation, for cooling in many types of machines and industry processes and for cleaning etc.  Liquids exhibit many characteristics that help us understand their nature.  Liquids have low compressibility, lack of Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.2 The Liquid State Liquids  Possess low compressibility, lack rigidity, and have high density compared with gases  Surface tension: Resistance of a liquid to an increase in its surface area  Liquids with large intermolecular forces tend to have high surface tensions Copyright ©2017 Cengage Learning. All Rights Reserved. Copyright © Cengage Learning. All rights reserved 30 Section 10.2 The Liquid State Liquids  Polar liquids typically exhibits capillary action – the spontaneous rising of a liquid in a narrow tube:  Two different types of forces are responsible for this property: cohesive forces and adhesive forces  Cohesive forces – intermolecular forces among the molecules of the liquid.  Adhesive forces – forces between the liquid molecules and their container. Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.2 The Liquid State Liquid….Continue  For example, a glass surface contains many oxygen atoms with partial negative charges that are attractive to the positive end of a polar molecules such as water.  The ability of the water to “wet” glass makes it creep up the walls of the tube where the water surface touches the glass. This however, tends to increase the surface area of the water, which is opposed by cohesive forces that try to minimize the surface.  Thus because water has both strong cohesive (intermolecular) forces and strong adhesive forces to glass, it “pulls itself” up a glass capillary tube (a tube with a small diameter) toLearning. Copyright ©2017 Cengage a height where the weight All Rights Reserved. Section 10.2 The Liquid State Convex Meniscus Formed by Nonpolar Liquid Mercury  A non-polar liquid such as mercury (Figure on the right) shows a convex meniscus. This  Behavior is characteristic of a liquid in  Which the cohesive forces are stronger than adhesive forces towards glass  Which force dominates alongside  the glass tube – cohesive or  adhesive forces? Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.2 The Liquid State Concave Meniscus Formed by Polar Water  The concave shape of the meniscus (figure on the right) shows that water’s Adhesive forces towards the glass are Stronger than its cohesive fors  Which force dominates alongside  the glass tube – cohesive or adhesive forces  adhesive forces? Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.2 The Liquid State Liquids….Continue  Another property of liquids which strongly depends on intermolecular forces is “Viscosity”, a measure of liquid’s resistance to flow.  Viscosity – measure of a liquid’s resistance to flow:  Liquids with large intermolecular forces or molecular complexity tend to be highly viscous. Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.2 The Liquid State Structural Model for Liquids  The development of a structural model for liquids present greater challenge than other two states of matter.  In the gaseous state, the particles are so far apart and are moving so rapidly that intermolecular forces are negligible under most circumstances. This means we can use simple model for gases.  In the solid-state, although the intermolecular forces are large, the molecular motions are minimal, and fairly simple models are again possible.  The liquid state, however, has both strong intermolecularCopyright forces andLearning. ©2017 Cengage significant All Rights Reserved.molecular Section 10.2 The Liquid State Structural Model for Liquids…Continue  Recent advances in Spectroscopy, the study of the manner in which substances interact with electromagnetic radiation, make it possible to follow the very rapid changes that occur in the liquids. As a result, our models of liquids are becoming more accurate. Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.3 An Introduction to Structures and Types of Solids Classification of Solids  There are many ways to classify solids; but the broader categories are amorphous solids and crystalline solids.  Amorphous solids: Have considerable disorder in their structures  Crystalline solids: Characterized by highly regular arrangement of components  Positions of components are represented by lattices  Lattice: Three-dimensional system of points designating positions of components that make up the substance Copyright ©2017 Cengage Learning. All Rights Reserved.  Learning. All rights reserved Copyright © Cengage 38 Section 10.3 An Introduction to Structures and Types of Solids Three Cubic Unit Cells and the Corresponding Lattices Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.3 An Introduction to Structures and Types of Solids Types of Crystalline Solids  Ionic solids: Possess ions at the lattice points that describe the structure of the solid  Molecular solids: Possess discrete covalently bonded molecules at the lattice points  Atomic solids: Possess atoms at the lattice points that describe the structure of the solid Copyright ©2017 Cengage Learning. All Rights Reserved. Copyright © Cengage Learning. All rights reserved 40 Section 10.3 An Introduction to Structures and Types of Solids Figure - Examples of Three Types of Crystalline Solids, only parts of the structure is shown in each case  (a) An atomic solid (b) An ionic solid (c) A molecular solid. The dotted lines show the hydrogen bonding interactions among the polar water molecules. C(a). All rights reserved Copyright ©2017 Cengage Learning. All Rights Reserved. 41 Section 10.3 An Introduction to Structures and Types of Solids Classification of Atomic Solids  Metallic solids - Possess a special type of delocalized non-directional covalent bonds  Network solids - Possess atoms bonded by strong directional covalent bonds  Bonds lead to giant molecules of atoms  Group 8A solids - Possess noble gas elements that are attracted to each other by London dispersion forces Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.4 Structure and Bonding in Metals Bonding Models for Metals  Metals are characterized by high thermal and electrical conductivity, malleability (capability of being shaped or extended) and ductility (The physical property of a metal that can be drawn into the thin wire ). These properties can be traced to the non-directional covalent bonding found in metallic crystals.  A metallic crystal can be pictured as containing spherical atoms packed together and bonded to each other equally in all directions.  Such an arrangement isLearning. Copyright ©2017 Cengage called closest packing. All Rights Reserved. Section 10.4 Structure and Bonding in Metals Bonding Models for Metals  A successful bonding model for metals must consider:  Malleability  Ductility  Efficient and uniform conduction of heat and electricity in all directions.  Although, the shapes of most pure metals can be changed relatively easily, most metals are durable and have high melting points.  These facts indicate that the bonding in most metals is strong and non-directional. That is, although it Copyright is difficult to separate metals atoms, ©2017 Cengage Learning. All Rights Reserved.  Section 10.4 Structure and Bonding in Metals Bonding Models for Metals…Continue  The simplest picture that explains these observations is the “Electron Sea Model” which Envisions a regular array of metal cations in a “sea” of valence electrons (See in the next picture: This model proposes that all the metal atoms in a metallic solid contribute their valence electrons to form a "sea" of electron. The electrons present in the outer energy levels of the bonding metallic atoms are not held by any specific and can move easily from one atom to the next.  The Mobile electrons can conduct heat and electricity  And the Metal ions can be freely moved around as Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.4 Structure and Bonding in Metals Figure - Depiction of Electron Sea Model for metals postulates a regular array of cations in a “sea” of valence electrons. Representation of an alkali metal Representation of an alkaline earth (Group 1A) with one valence metal (Group 2A) with two valence electron electrons Copyright ©2017 Cengage Learning. All Rights Reserved. Section 10.4 Structure and Bonding in Metals Metal Alloys  Because of the nature of the structure and bonding of metals, other elements can be introduced into a metallic crystal relatively easily to produce substances called alloys.  Alloy: Best defined as: Substance that contains a mixture of elements and possesses metallic properties. Alloys are classified into two types: Copyright ©2017 Cengage Learning. All Rights Reserved. Copyright © Cengage Learning. All rights reserved 47 Section 10.4 Structure and Bonding in Metals Metal Alloys…Continued  Substitutional alloy: Some of the host metal atoms are replaced by other metal atoms of similar size. For example, in brass, approximately one-third of the atoms in the host copper metal have been replaced by zinc atoms (See the next Figure).  Interstitial alloy: is formed when some of the interstices in the closest packed metal structure are occupied by small atoms; steel, is the best known interstitial ally example which contains carbon atoms in the holes of an iron crystal. TheCopyright presence of All ©2017 Cengage Learning. interstitial Rights Reserved. atoms Section 10.4 Structure and Bonding in Metals Figure – Examples of Two Types of Alloys Copyright ©2017 Cengage Learning. All Rights Reserved. Copyright © Cengage Learning. All rights reserved 49 Section 10.4 Structure and Bonding in Metals Influence of Carbon on the Properties of Steel  Mild steel - Contains less than 0.2% carbon  Malleable and ductile  Used for nails, cables, and chains  Medium steel - Contains 0.2 to 0.6% carbon  Used in rails and structural steel beams  High-carbon steel - Contains 0.6 to 1.5% carbon Copyright ©2017 Cengage Learning. All Rights Reserved.