Chapter 17: Chemistry

Chemistry

What is Chemistry?

• the study of matter and the transformations it undergoes

Chemistry is the Central Science

• Agricultural Science

• Biochemistry

• Medicine

• Forensic Science

• Solid-state physics

• Environment

• Chemical Engineering

• Atmospheric Science

Basic Research

• leads to better understanding of the natural world

• is a foundation that leads to useful applications

Applied Research

• focuses on developing applications built upon the principles discovered through basic research

• has led to most goods that characterize modern life

The Submicroscopic World

• macroscopic: large enough to be seen

• micoscopic: only seen with a microscope

• submicroscopic: even smaller

  • atoms and molecules

  • molecule = atoms linked together

States of Matter

• Solids

  • 3D arrangement

  • not flexible

  • no flow

  • the particles vibrate, but can’t move past each other

  • particles have a solid shape

• Liquids

  • holds the shape of the container

  • flexible

  • flows

  • particles can flow and take the shape of the container

• Gases

  • no shape

  • flexible

  • flows

  • atoms have no attraction, but can be pushed together

  • particles can go anywhere

Changes

• Why do the Changes happen?

  • in order to change the phase of a substance you must either add or remove heat

  • adding heat - melting and evaporation

  • removing heat - condensation and freezing

• Why do the changes happen?

  • Cause of the phase change = transfer of energy

  • Heat of Fusion

    • energy needed to change any substance from solid to liquid (and vice versa)

  • Heat of Vaporization

    • energy needed to change any substance from liquid to gas (and vice versa)

Chemical VS. Physical

• Physical

  • color

  • hardness

  • density

  • texture

  • phase

• Chemical

  • ability to react with other substances

  • ability to transform into other substances

Changes

• Physical

  • the substance may change phase

  • the substance may change a physical property (color, hardness, density, texture)

  • the substance still has the same chemical identity

• Chemical (Terms)

  • Chemical Bond

    • the force of attraction between two atoms that holds them together in a molecule

  • Chemical Changes

    • rearrangement of the way atoms are bonded

  • Chemical Reaction

    • Another term for chemical change - new materials are formed

  • The chemical bonds of the substance change

  • the materials undergo a chemical reaction

• How do I know?

  • After a Physical change…

    • the molecules are the same

  • After a chemical change…

    • the molecules have changes

• I can’t see molecules!

  • If I restore the original conditions does the original appearance return?

    • If so…then it’s a physical change

    • If not…then it’s a chemical change

  • Have new materials been formed?

    • If so…then it’s a chemical change

    • If not…then it’s a physical change

Periodic Table

• Describe the Periodic Table

  • the roadmap of chemistry

  • arranges all the known elements in a logical pattern

• The Logical Pattern

  • elements arranged in order of increasing atomic number

    • the number of protons in the nucleus

  • usually coincides with increasing atomic mass

    • the total mass of the atom

    • (mass of protons + neutrons)

• How do I read the Periodic Table?

  • Atomic number

    • The number of protons in an atom

    • identifies element

      • also determines number of electrons, assuming it isn’t an atom

• Why is atomic number based on protons? Why not neutrons?

  • Isotope

    • different “versions” of the same element

    • # of protons always the same

    • # of neutrons varies

    • differ in atomic mass, NOT chemical properties

• How do I read the Periodic Table?

  • Atomic Mass

    • protons and neutrons (electrons)

    • average mass is given in atomic mass units (“amu”) AKA Daltons

    • a decimal number because it is an average of all the isotopes of the elements

• How do I know how many neutrons are in an atom?

  • use atomic mass and atomic number

    • atomic mass units (“amu”) = protons + neutrons

    • rounded atomic mass - atomic number = neutrons

• How do I read the periodic table?

  • Atomic symbol

    • one or two letters to represent the element

    • used around the world

    • usually the abbreviation of the element

      • OR

    • The abbreviated Latin name of the element

• The Divisions

  • North to South - East to West

  • Organization tells us a lot about the elements

  • 7 rows

    • periods

    • shows trends across table

    • as you go lower left to upper right

      • size of atoms increases

    • atoms lose elwctrons easily

  • 18 columns

    • groups or families

    • similar chemical properties

    • as you go columns left to right

      • metals

      • metalloids

      • nonmetals

• neutrons just hang out and add mass - determine isotopes

• protons give each element its number - atomic number

• electrons give each element its location - periods - families

• Metals - includes most elements - shiny, opaque, good conductors, malleable

• Nonmetals - between the metals and nonmetals, metallic and nonmetallic characteristics

Periodic Table Groups

• Group 1: Alkali Metals

  • metals

  • from Araabic word for ashes “al-quali”

  • mixtures used to make soap

• Group 2: Alkaline--Earth Metals

  • metals

  • also form alkaline solutions when mixed with water

  • don’t melt in fire

  • named “earth” by midieval alchemists

• Groups 3-12: Transition Metals

  • metals

  • do not form alkaline solutions with water

  • used for structural purposes

  • include some familiar, important elements

• Inner Transition Metals

  • subset of 6th and 7th periods

  • metals

  • removed so the table isnt so large

  • 6th Period:

    • Lanthanides (LED’s)

    • difficult to purify

  • 7th Period:

    • actinides

    • nuclear power

    • difficult to purify

• Group 16: Chalcogens

  • metalloids/nonmetals

  • Chalcogens means “ore-forming” in Greek

  • top two in this group commonly found in ores

• Group 17: Halogens

  • mostly nonmetals

  • Halogen means “salt-forming” in Greek

  • commonly form salts

• Group 18: Noble Gases

  • gases

  • unreactive, tend to not combine with other elements

  • “noble” - medieval times

• Didn’t we miss a few groups?

  • Groups 13-15??

  • no common names for these families

Review and Background

• What’s the difference between an “element” and an “atom”?

  • Element

    • more than one of only one kind of atom

    • a pure group of atoms

    • macroscopic or microscopic

  • Atom

    • only one

    • submicroscopic

• Lingo #1 - Elemental Formulas

  • Used to represent elements…

    • use atomic symbol

    • gold = Au

    • lithium = Li

  • multiple atoms bonded together (Molecules)

    • atomic symbols + subscript telling the number of each kind of atoms

    • two nitrogen atoms = N2

    • sulfur = S8

• Lingo #2: Compounds

  • …Atoms of different elements bonded together

    • sodium atoms + Chlorine Atoms = Sodium Chloride (table salt)

    • Nitrogen atoms + Hydrogen Atoms = ammonia (household cleaner)

• Lingo #3: Chemical Formulas

  • …USed to Represent a compound

    • Symbols written together

      • sodium chloride = NaCl

      • Ammonia - NH3

• Lingo #4: Properties of Compounds

  • …Different properties as a compound than when separate

    • chemical change = created something new with new properties

    • NaCl

      • sodium = a metal thay reacts violently with water

      • chlorine = a very toxic gas

      • Bond them together? table salt

Naming Compounds

• Names tell what the compound contains and how they are joined

  • First, the element further to the left on the table

  • Then, the element farther to the right

  • Add “-ide” to the end of the second element

  • NaCl = sodium chloride

  • MgO = magnesium oxide

• Prefixes tell how many atoms of an element in a compound

  • “mono-” is often dropped from the beginning of the first word

• Many Compounds use common names

  • H2O - water

  • CH4 - methane

Questions from the Quiz

• At the microscopic level, solid, liquid, and gaseous phases are distinguished by how the submicroscopic particles hold together

  • True

• A solid at 25 degrees Celsius has stronger attractions among its submicroscopic particles than does a liquid substance at 25 degrees Celsius

  • True

• The Phase of matter in which atoms and moelcules no longer move is the:

  • none of the phases