Chemistry 112
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Chemistry 112. Overview of Chapters 1-4. Chapter 1 Highlights. Chemistry is the study of matter, the physical substance of all materials. The building blocks of matter are atoms, which combine to form compounds.

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Chemistry 112

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Chemistry 112

Chemistry 112

Overview of Chapters 1-4


Chapter 1 highlights

Chapter 1 Highlights

  • Chemistry is the study of matter, the physical substance of all materials.

  • The building blocks of matter are atoms, which combine to form compounds.

  • The different types of atoms are called elements, which are arranged systematically in the periodic table.


Chapter 1 highlights cont

Chapter 1 Highlights (cont)

  • Atoms are composed of protons, neutrons, and electrons.

  • All atoms of the same element contain the same number of protons (and electrons) but may vary in the number of neutrons.

  • The protons and neutrons are found inside the tiny but dense nucleus, whereas the electrons are found in orbitals outside the nucleus.


Chapter 1 highlights cont1

Chapter 1 Highlights (cont)

  • The arrangement of electrons in the orbitals is called the electronic configuration and determines the chemistry of an atom.


Types of matter

Types of Matter


States of matter

States of Matter


Chemistry 112

  • Chemistry and Matter

    • Physical Changes versus Chemical Changes

      • Physical changes involve changes in appearance (i.e., changes in state such as melting).

      • Chemical changes result in new substances.


Chemistry 112

  • The Building Blocks of Matter

    • Atoms

      • Smallest representative units of the elements.

    • Compounds

      • Different atoms linked together; e.g., H2O.


Chemistry 112

  • The Building Blocks of Matter (cont)

    • Dalton’s Atomic Theory

      • All matter is composed of indivisible atoms.

      • All atoms of one element are identical to each other but different than the atoms of other elements.

      • Compounds are formed when atoms of different elements combine in whole number ratios.

      • Atoms are rearranged during chemical reactions but atoms cannot be created or destroyed.


Chemistry 112

  • The Periodic Table

    • Used to organize the elements by recurring chemical properties.

    • Elements in the same vertical column of the periodic table have similar chemical properties and are said to be in the same group or family.


The periodic table

The Periodic Table


Chemistry 112

  • The Atom

    • Components

      • Positive protons, negative electrons, and neutral neutrons

    • Atomic Number

      • The number of protons in an atom, which determines what element it is

    • Mass Number

      • Number of protons + the number of neutrons


Chemistry 112

  • The Atom (cont)

    • Isotopes

      • Isotopes of the same element have the same number of protons but differ in the number of neutrons.

    • Atomic Mass

      • The atomic mass for each element on the periodic table reflects the relative abundance of each isotope in nature.


Isotopes

Isotopes


Chemistry 112

  • Models of the Atom

    • The Plum Pudding Model

      • Electrons are embedded in a sphere of positive charge.

    • The Nuclear Model

      • All of the positive charge is in a tiny central nucleus with electrons outside the nucleus.

      • This model was developed by Rutherford after his landmark experiment.


The rutherford experiment

The Rutherford Experiment


Chemistry 112

  • Models of the Atom (continued)

    • Bohr’s Solar System Model

      • Electrons circle the nucleus in orbits, which are also called energy levels.

      • An electron can “jump” from a lower energy level to a higher one upon absorbing energy, creating an excited state.

      • The concept of energy levels accounts for the emission of distinct wavelengths of electromagnetic radiation during flame tests.


The solar system model

The Solar System Model


Electromagnetic radiation

Electromagnetic Radiation


Chemistry 112

  • Models of the Atom (continued)

    • The Modern Model

      • Orbits are replaced with orbitals, volumes of space where the electrons can be found.

      • The arrangement of electrons in the orbitals is the electronic configuration of an atom, which determines the chemistry of an atom.


The orbital model electronic configurations

The Orbital Model:Electronic Configurations


Chapter 2 highlights

Chapter 2 Highlights

  • Having eight valence electrons is particularly desirable (“the octet rule”).

  • Atoms form bonds with other atoms to satisfy the octet rule.

  • The two major types of chemical bonds are ionic and covalent.


Chapter 2 highlights cont

Chapter 2 Highlights (cont)

  • Electronegativity is the ability to attract shared electrons.

  • The type of bond formed between two atoms depends on their difference in electronegativity.

  • Ionic bonds form between atoms with a large difference in electronegativity (generally a metal and a nonmetal).


Chapter 2 highlights cont1

Chapter 2 Highlights (cont)

  • Nonpolar covalent bonds form between atoms with little difference in electronegativity (generally two nonmetals).

  • Polar covalent bonds form between atoms with intermediate difference in electronegativity.

  • There are many ways to depict molecules.


Chemistry 112

  • The Octet Rule

    • Atoms with eight valence electrons are particularly stable, an observation called the octet rule.

    • Atoms form bonds with other atoms to achieve a valence octet.


Electronic configuration of noble gases

ElectronicConfiguration of Noble Gases


Types of compounds

Types of Compounds


Lewis dot structures

Lewis Dot Structures


Chemistry 112

  • Ionic Bonds

    • Ionic compounds result from the loss of electrons by one atom (usually a metal) and the gain of electrons by another atom (usually a nonmetal).

    • Ionic bonds arise from the attraction between particles with opposite charges(electrostatic forces); e.g., Na+ Cl-.


Ionic compounds

Ionic Compounds


Chemistry 112

  • Covalent Bonds

    • Covalent bonds are formed when two atoms share one or more electron pairs.

    • When two atoms share one pair of electrons, the result is a single bond.

    • Two shared pairs of electrons is a double bond; three is a triple bond.


Chemistry 112

  • Equal Sharing versus Unequal Sharing

    • When two different kinds of atoms are bonded, the electrons are usually shared unequally.

    • When a bond exists between two identical kinds of atoms, the electrons are shared equally.

    • An atom with greater electronegativity has a greater ability to attract shared electrons.


Electronegativity

Electronegativity


Polar vs nonpolar bonds

Polar vs. Nonpolar Bonds


Chemistry 112

  • Representing Structures

    • In a structural formula, atoms are represented by chemical symbols, and bonds are represented by lines.

    • In a line drawing, any point where lines connect or terminate is understood to be a carbon atom with sufficient bonded hydrogen atoms to achieve the four bonds necessary for carbon.


Drawing molecules

Drawing Molecules


Chapter 3 highlights

Chapter 3 Highlights

  • Reaction equations have with the initial materials (reactants) on the left, followed by a reaction arrow pointing from left to right, and the final materials (products) on the right.

  • A balanced equation has the same number and kinds of atoms on both sides of the equation.


Chapter 3 highlights1

Chapter 3 Highlights

  • The relationship between the amounts of reactants and products is the stoichiometry, which comes from a balanced reaction equation.

  • The SI unit for measuring atoms and molecules is the mole.

  • In an oxidation-reduction reaction, electrons are transferred from one material (the substance that is oxidized) to another material (the substance that is reduced).


Chemistry 112

Na + Cl NaCl

  • Balanced Reaction Equations

    • Writing a Chemical Reaction

      • The starting materials, the reactants, are written on the left.

      • The materials that are produced, the products, are written on the right.

      • Reactants are separated from products by a horizontal arrow pointing from left to right.

Reactants Product


Chemistry 112

Incorrect

H2 + O2 H2O

2 H2 + O2 2 H2O

Correct

  • Balanced Reaction Equations (cont)

    • Balancing the Equation

      • The law of conservation of matter states that matter can neither be created nor destroyed in a chemical reaction.

      • The number and kind of atoms on the left-hand side of an equation must be equal to the number and kind of atoms on the right.


Chemistry 112

  • Balanced Reaction Equations (cont)

    • Stoichiometry

      • The stoichiometry of a chemical reaction is the relationship between the number of molecules of the reactants and products in the balanced reaction equation.

      • A reactant present in insufficient amounts is the limiting reagent.


Chemistry 112

  • The Mole

    • The mole is the SI unit of measure to describe the amount of matter that is present.

    • One mole is equal to 6.02 x 1023 particles (Avogadro’s number).

    • One mole of an element has a mass that is equal to the atomic mass of that element in grams.

    • One mole of a compound has a mass that is equal to the molecular/formula mass of that compound in grams.


The mole

The Mole


Chemistry 112

  • Stoichiometry Calculations

    • The units of molar mass are grams/mole.

    • Moles x molar mass = mass.

      • Example: 2.0 mol CO2 x 44 g/mol = 88 g CO2

    • Mass/molar mass= moles.

      • Example: 132 g CO2 / 44 g/mol = 3.0 mol CO2


Chemistry 112

  • Stoichiometry Calculations

    • The expected mass of a product or reactant can be calculated for any reaction by using the balanced equation and the molar mass.


Chemistry 112

  • Oxidation-Reduction Reactions

    • Defined

      • Oxidation-reduction (“redox”) reactions involve the transfer of electrons from one substance to another.

      • Oxidized substances lose electrons and reduced substances gain electrons.


Oxidation reduction

Oxidation-Reduction


Chemistry 112

  • Oxidation-Reduction Reactions (cont)

    • The Chemistry of Batteries

      • Combining a readily oxidized substance with an easily reduced substance can create a battery.

      • The oxidized material is the anode and the reduced material is the cathode of the battery.


Batteries

Batteries


Chapter 4 highlights

Chapter 4 Highlights

  • Intermolecular forces hold the molecules of a material together.

  • Stronger intermolecular forces lead to higher melting and boiling temperatures.

  • The relative strengths of intermolecular forces generally follow the trend:

    hydrogen bonds > dipole-dipole interactions > London forces


Chapter 4 highlights cont

Chapter 4 Highlights (cont)

  • Like dissolves like. That is, polar solutes dissolve in polar solvents.

  • Acids are proton (H+) donors; bases are proton acceptors that produce OH- in solution.

  • The pH measures the acidity of a solution: pH < 7.0 is acidic; pH > 7.0 is basic; pH = 7.0 is neutral.

  • Acids react with bases in neutralization reactions.


Chemistry 112

  • States of Matter

    • Review of Types of Bonds

      • Chemical bonds (intramolecular forces) hold atoms together.

      • The three types of chemical bonds are ionic, polar covalent, and nonpolar covalent.

      • Intermolecular forces hold molecules together.


Review of types of bonds

Review of Types of Bonds


Chapter outline

Chapter Outline

  • States of Matter (cont)

    • Particle Cohesion Determines Physical State

      • In general, the relative strengths of intermolecular forces follows the trend:

        gases < liquids < solids

    • Changes of State

      • Adding energy breaks intermolecular forces and causes molecules to change their state.

      • The stronger the intermolecular forces of a compound, the higher are the melting and boiling points.


Changes of state

Changes of State


Chemistry 112

  • Types of Intermolecular Forces within Pure Substances

    • London dispersion forces

      • A temporary dipole in one molecule can induce a dipole in a neighboring molecule.

      • The negative end of one temporary dipole can attract the positive end of an induced dipole; these attractions are called London dispersion forces.

      • London forces tend to be fairly weak.


London dispersion forces

London Dispersion Forces


Chemistry 112

  • Types of Intermolecular Forces within Pure Substances (cont)

    • Dipole-dipole interactions

      • Dipole-dipole interactions exist between molecules with polar covalent bonds.

      • Dipole-dipole interactions are typically stronger than London dispersion forces.


Dipole dipole interactions

Dipole-Dipole Interactions


Chemistry 112

  • Types of Intermolecular Forces within Pure Substances (cont)

    • Hydrogen Bonds

      • Hydrogen bonds are a special type of dipole-dipole interaction.

      • Hydrogen bonds can occur when H is bonded to one of the highly electronegative atoms N, O, or F. An example is H2O.

      • Hydrogen bonds are typically quite strong.


Hydrogen bonds in water

Hydrogen Bonds in Water


Mixtures

Mixtures


Chemistry 112

  • Forming Solutions

    • Like dissolves like

      • Ionic solutes often dissolve in polar solvents;e.g., NaCl dissolves in H2O.

      • Polar solutes generally dissolve in polar solvents; e.g., NH3 in H2O.

      • Nonpolar solutes generally do not dissolve well in polar solvents; e.g., oil in H2O.


Nacl dissolving in h 2 o

NaCl Dissolving in H2O


Chemistry 112

  • Emulsions

    • Emulsifying agents are molecules that contain a polar portion and a nonpolar region.

    • Soap is an example of an emulsifying agent that can form a suspension of a nonpolar material in a polar solvent (an “emulsion”).


Emulsification with soap

Emulsification with Soap


Chemistry 112

  • Measuring Amounts in Solution

    • Solubility

      • The maximum amount of a solute that dissolves in a solvent

    • Molarity

      • The amount of a solute dissolved in a solvent is its concentration.

      • Concentration is often measured in moles/liter, also called molarity (M).


Chemistry 112

  • Acid-Base Chemistry

    • Definitions of Acids and Bases

      • Acids turn litmus paper red; bases turn litmus paper blue.

      • Acids produce H+ in solution; bases produce OH- in solution.

      • Acids are proton donors; bases are proton acceptors.


Chemistry 112

  • Acid-Base Chemistry (cont)

    • The pH Scale: a measure of acidity


Chemistry 112

  • Acid-Base Chemistry (cont)

    • Acid-Base Indicators

      • Molecular sensors of H+.

H+


Chemistry 112

  • Acid-Base Chemistry (cont)

    • Neutralization Reactions: equal molar amounts of an acid and a base react to form a neutral solution.

HCl + NaOH NaCl + H2O


Chemistry 112

  • Acid-Base Chemistry (cont)

    • Buffers: contain a weak acid and its conjugate base, which react with added H+ or OH- to prevent pH changes.

HA H+ + A-

  • Adding acid:H+ reacts with A- to make more HA

  • Adding base:OH- reacts with HAto make more A- and H2O


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