Physical States of Matter CHAPTER 7 Physical States of Matter General, Organic, & Biological Chemistry Janice Gorzynski Smith

CHAPTER 7: Physical States of Matter Learning Objectives: States of matter: Gas, Liquid, Solid Intermolecular forces: London dispersion Dipole-dipole Hydrogen bonding Gas behavior Combined gas law, Ideal gas law, Dalton’s law of partial P Liquid behavior Viscosity, surface tension, vapor pressure Solid behavior Crystalline vs Amorphous Solids Phase changes Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Matter Gas, Liquid, Solid Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Matter Gas, Liquid, Solid Existing as a gas, liquid, or solid depends on: The balance between the kinetic energy of its particles. The strength of the interactions between the particles. Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Matter Intermolecular Forces Intermolecular forces are the attractive forces that exist between molecules. In order of increasing strength, these are: London dispersion forces Dipole–dipole interactions Hydrogen bonding 4. Ion-Dipole & Ion-Ion interactions Use modeling kit! The strength of the intermolecular forces determines whether a compound has a high or low melting point and boiling point, and thus whether it is a solid, liquid, or gas at a given temperature. Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Matter London Dispersion Forces More e− density in one region creates a partial negative charge (δ−). Less e− density in one region creates a partial positive charge (δ+). Use modeling kit! London dispersion forces are very weak interactions due to the momentary changes in electron densityin a molecule. Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Matter Dipole-Dipole Interactions Dipole–dipole interactions are the attractive forces between the permanent dipoles of two polar molecules. Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Matter Hydrogen Bonding Hydrogen bonding occurs when a hydrogen atom bonded to O, N, or F is electrostatically attracted to an O, N, or F atom in another molecule. Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Matter Hydrogen Bonding Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Matter Ion-Dipole interactions Attractions between ion and charged end of polar molecules Use modeling kit! (a) Negative ends of water dipoles surround cation (b) Positive ends of water dipoles surround anion Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Matter Strength of Intermolecular Attractions The boiling point is the temperature at which a liquid is converted to the gas phase. The melting point is the temperature at which a solid is converted to the liquid phase. The stronger the intermolecular forces, the higher the boiling point and melting point. Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Gas < Liquids < Solids Matter Intermolecular Attractions in Gases, Liquids, & Solids London Dispersion Forces Dipole-Dipole Forces Hydrogen Bonds Ion-Dipole Forces Weakest Strongest Use modeling kit! Gas < Liquids < Solids Increasing Average Kinetic Energy Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Gases Kinetic Molecular Theory A gas consists of particles that move randomly and rapidly. The size of gas particles is small compared to the space between the particles. Gas particles exert no attractive forces on each other. The kinetic energy of gas particles increases with increasing temperature. Use modeling kit! When gas particles collide with each other, they rebound and travel in new directions. Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Gases Pressure When gas particles collide with the walls of a container, they exert a pressure. Pressure (P) is the force (F) exerted per unit area (A). Force F Pressure = = Area A Use modeling kit! 760. mm Hg 760. torr 1 atmosphere (atm) = 14.7 psi 101,325 Pa Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Gases Gas Laws Boyle’s Law T1 = T2 P1V1 = P2V2 Charles’ Law P1 = P2 Gay-Lussac’s Law V1 = V2 Avagadro’s Law Combined Gas Law Use modeling kit! V V1 V2 = k = n n1 n2 Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Gases The Combined Gas Law P1V1 P2V2 = T1 T2 initial conditions new conditions This equation is used for determining the effect of changing two factors (e.g., P and T) on the third factor (V). Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Gases Ideal Gas Law All four properties of gases (i.e., P, V, n, and T) can be combined into a single equation called the ideal gas law. PV = nRT R is the universal gas constant: L • atm mol • K For atm: R = 0.0821 Use modeling kit! L • mm Hg mol • K For mm Hg: R = 62.4 Smith. General Organic & Biolocial Chemistry 2nd Ed.

Standard Temperature & Pressure Gases Standard Temperature & Pressure Often amounts of gas are compared at a set of standard conditions of temperature and pressure, abbreviated as STP. STP conditions are: 1 atm (760 mm Hg) for pressure 273 K (0 oC) for temperature At STP, 1 mole of any gas has a volume of 22.4 L. 22.4 L is called the standard molar volume. Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Gases Dalton’s Law of Partial Pressures Dalton’s law: The total pressure (Ptotal) of a gas mixture is the sum of the partial pressures of its component gases. For a mixture of three gases A, B, and C: Ptotal = PA + PB + PC Use modeling kit! partial pressures of A, B, and C Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Liquids Vapor Pressure Vapor pressure is the pressure exerted by gas molecules in equilibrium with the liquid phase. Use modeling kit! Vapor pressure increases with increasing temperature. The boiling point of a liquid is the temperature at which its vapor pressure = 760 mmHg. Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Liquids Vapor Pressure The stronger the intermolecular forces, the lower the vapor pressure at a given temperature. Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Liquids Viscosity Viscosity is a measure of a fluid’s resistance to flow freely. Compounds with strong intermolecular forces tend to be more viscous than compounds withweaker forces. Substances composed of large molecules tend to be more viscous, too, because large molecules do not slide past each other as freely. Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Liquids Surface Tension Surface tension is a measure of the resistance of a liquid to spread out. Interior molecules in a liquid are surrounded by intermolecular forces on all sides. Surface molecules only experience intermolecular forces from the sides and from below. Use modeling kit! Stronger intermolecular forces the higher the surface tension Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Solids Crystalline Solids An ionic solid is composed of oppositely charged ions (NaCl). A molecular solid is composed of individual molecules arranged regularly (H2O). Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Solids Crystalline Solids A network solid is composed of a vast number of atoms covalently bonded together (SiO2). A metallic solid is a lattice of metal cations surrounded by a cloud of e− that move freely (Cu). Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Solids Amorphous Solids Amorphous solids have no regular arrangement of their particles. They can be formed when liquids cool too quickly for regular crystal formation. Very large covalent molecules tend to form amorphous solids, because they can become folded and intertwined. Use modeling kit! Examples include rubber, glass, and plastic. Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Matter Summary of Properties Property of s, l, g Increases Decreases Example Boiling Point increasing total intermolecular forces decreasing total intermolecular forces Water has a high boiling point because it has H-bonding, dipole, and dispersion forces. It is close to heptane (C7H16), a heavier molecule that only experiences dispersion forces . Melting Point The melting point of ionic solids is extremely high compared to water which experiences all other intermolecular forces, but not ion-dipole forces. (NaCl is 1074 K and water is 273 K) Retention of V & Shape Increasing intermolecular forces and decreasing T & P Decreasing intermolecular forces, and increasing kinetic energy of particles or T & P Gases will fill the volume and shape of the container that holds them, while solids will retain their own shape and volume regardless of the container. Surface Tension with increasing intermolecular forces with decreasing intermolecular forces The molecules on the surface have less neighbors (and therefore less stabilizing intermolecular forces) and so have a higher potential energy, which the material will try to reduce with its shape (sphere): water beading. Viscosity increasing intermolecular forces and decreasing temperature decreasing intermolecular forces and decreasing temperature Not just a property of liquids, also gases and solids. Amorphous solids change shape over time because of their viscosity. Vapor Pressure Decreasing intermolecular forces and increasing temperature Increasing intermolecular forces and decreasing temperature Ether has weaker intermolecular forces than water and a higher vapor pressure, so it evaporates much faster then water. Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Phase Change Summary of Phase Changes fusion evaporation SOLID LIQUID GAS freezing condensation deposition sublimation Use modeling kit! endothermic System absorbs energy from surrounds in the form of heat Requires the addition of heat exothermic System releases energy into surrounds in the form of heat or light Requires heat to be decreased Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Phase Change Solid  Liquid Use modeling kit! solid water liquid water The amount of energy needed to melt 1 gram of a substance is called its heat of fusion. Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Phase Change Liquid  Gas Use modeling kit! liquid water gaseous water The amount of energy needed to vaporize 1 gram of a substance is called its heat of vaporization. Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Phase Change Solid  Gas Use modeling kit! gaseous CO2 solid CO2 Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Phase Change Heating Curve Use modeling kit! A heating curve shows how a substance’s temperature changes as heat is added. Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Phase Change Cooling Curve Use modeling kit! A cooling curve shows how a substance’s temperature changes as heat is removed. Smith. General Organic & Biolocial Chemistry 2nd Ed.

Smith. General Organic & Biolocial Chemistry 2nd Ed. Phase Change Energy & Phase Changes Use modeling kit! Smith. General Organic & Biolocial Chemistry 2nd Ed.