Chapter 7 How Molecules Mix Lecture Presentation Chapter 7 How Molecules Mix Bradley Sieve Northern Kentucky University Highland Heights, KY

7.1 Four Different Types of Dipole Attractions Electron unevenly distributed in a molecule Extreme cases are present in ionic compounds Water exhibits a weaker dipole type called a polar molecule

7.1 Four Different Types of Dipole Attractions Molecular Attractions Involving Dipoles

7.1 Four Different Types of Dipole Attractions Ion-Dipole Attractions Interaction between ionic charge and molecular dipole

7.1 Four Different Types of Dipole Attractions Collective attraction from many molecules

7.1 Four Different Types of Dipole Attractions Induced Dipole Attractions Dipole induced in a nonpolar molecule by surrounding dipole containing molecules

Concept Check How does the electron distribution in an oxygen molecule change when the hydrogen side of a water molecule is nearby?

Concept Check Because the hydrogen side of the water molecule is slightly positive, the electrons in the oxygen molecule are pulled toward the water molecule, inducing in the oxygen molecule a temporary dipole in which the larger side is nearer the water molecule (rather than as far away as possible)

7.1 Four Different Types of Dipole Attractions Dipole–Induced Dipole Attractions Interaction between a permanent dipole and a dipole–induced dipole Weaker than dipole–dipole attractions

Concept Check Distinguish between a dipole–dipole attraction and a dipole–induced dipole attraction.

Concept Check The dipole–dipole attraction is stronger and involves two permanent dipoles. The dipole–induced dipole attraction is weaker and involves both a permanent and temporary dipole.

7.1 Four Different Types of Dipole Attractions Induced dipole–induced dipole attractions Temporary dipoles are due to the momentary arrangement of electrons Temporary dipoles can induce dipoles on other nonpolar molecules Has largest effect in the largest atoms and molecules Also called dispersion forces

7.1 Four Different Types of Dipole Attractions

7.1 Four Different Types of Dipole Attractions

Concept Check Distinguish between a dipole–induced dipole attraction and an induced dipole–induced dipole attraction.

Concept Check The dipole–induced dipole attraction is stronger and involves both a permanent and temporary dipole. The induced dipole–induced dipole attraction is weaker and involves two temporary dipoles.

7.1 Four Different Types of Dipole Attractions

7.1 Four Different Types of Dipole Attractions

Concept Check Methanol, CH3OH, which can be used as a fuel, is not much larger than methane, CH4, but it is a liquid at room temperature. Suggest why. © 20## Pearson Education, Inc.

Concept Check The polar oxygen–hydrogen covalent bond in each methanol molecule leads to hydrogen bonding between molecules. These relatively strong interparticle attractions hold methanol molecules together as a liquid at room temperature.

7.2 A Solution Is a Single-Phase Homogeneous Mixture Homogenous mixture of a single phase Examples: Sugar dissolved in water is a liquid solution Gemstones are solid solutions Alloys are solid solutions Air is a gaseous solution

7.2 A Solution Is a Single-Phase Homogeneous Mixture

7.2 A Solution Is a Single-Phase Homogeneous Mixture Parts of a solution Solvent is the largest component of a solution Solute makes up the other components Sugar dissolved in water solution Water is the solvent Sugar is the solute

Concept Check What is the solvent in the gaseous solution we call air?

Concept Check Nitrogen is the solvent, because it is the component present in the greatest quantity.

7.2 A Solution Is a Single-Phase Homogeneous Mixture Types of solutions based on solute amount Saturated solution No more solute will dissolve in the solution Unsaturated solution Less solute present than will dissolve in the solution

7.3 Concentration Is Given as Moles per Liter The amount of solute dissolved per amount of solvent

7.3 Concentration Is Given as Moles per Liter Chemical amount of a substance Equal to 6.02 × 10−23 particles

7.3 Concentration Is Given as Moles per Liter Molarity Common unit of concentration Number of moles per liter of solution

Concept Check How many moles of sucrose are in 0.5 liter of a 2-molar solution? How many molecules of sucrose is this?

Concept Check You need to understand that 2-molar means 2 moles of sucrose per liter of solution. To obtain the amount of solute, you should multiply solution concentration by amount of solution: (2 moles/L)(0.5 L) = 1 mole, which is the same as 6.02 × 1023 molecules.

7.4 Solubility Is How Well a Solute Dissolves Ability of a solute to dissolve in a solvent If there is any appreciable amount, it is considered soluble Depends on number and types of interactions

7.4 Solubility Is How Well a Solute Dissolves Types of Solubility Infinitely soluble No practical point of saturation Insoluble Solute does not dissolve in solvent to any appreciable extent

7.4 Solubility Is How Well a Solute Dissolves Temperature Effects on Solubility Solubility increases with temperature due to increased kinetic energies Solid that forms upon cooling is called a precipitate

7.4 Solubility Is How Well a Solute Dissolves Solubility of gases Gas solubility decreases with increased temperature Due to the increased kinetic energy and the solute molecules escaping the solution

7.4 Solubility Is How Well a Solute Dissolves

7.5 Soap Works by Being Both Polar and Nonpolar Contains both polar and nonpolar ends Can interact with both polar and nonpolar grime Michelle forms to carry grime away in water

7.5 Soap Works by Being Both Polar and Nonpolar Soap is produced by the reaction of fats with NaOH Chemists create synthetic soaps called detergents

7.6 Softening Hard Water Hard Water Water containing large amounts of Ca and Mg Can form solid compounds, clogging pipes Leads to soap scum by binding the soap molecules Treatments include Addition of Na2CO3 to soap Water-softening system

7.6 Softening Hard Water Na2CO3 Treatment

7.6 Softening Hard Water Water-Softening Unit

7.7 Purifying the Water We Drink Purifying drinking water Utilizes physical properties or water and solutes Creating potable (drinkable) water is a several-step process

7.7 Purifying the Water We Drink Fresh water can be made from salt water Desalination is the removal of salt from water Primary methods include Distillation, which utilizes vaporization of the water Reverse osmosis, which passes water through a semipermeable membrane

7.7 Purifying the Water We Drink Home Distillation

7.7 Purifying the Water We Drink Reverse Osmosis external pressures push the water

7.7 Purifying the Water We Drink Bottled water More expensive than tap water Discarded water bottles are a large source of waste Often simply purified tap water from municipal sources