SCI 10

• Matter


  Anything that occupies space and has mass
• Substance


  A form of matter that has a definite composition and distinct properties
• Chemistry


  The study of matter and the changes it undergoes
• Substances


  • liquid nitrogen
  • gold ingots
  • silicon crystals
• Mixture


  A combination of two or more substances in which the substances retain their distinct identities
• Types of mixtures


  • Homogeneous mixture - composition of the mixture is the same throughout
  • Heterogeneous mixture - composition is not uniform throughout
• Mixtures


  • soft drink, solder
  • cement, iron filings in sand
  • Milk
• Physical means


  Can be used to separate a mixture into its pure components
• Physical separation methods


  • magnet
  • distillation
• Element


  A substance that cannot be separated into simpler substances by chemical means
• Elements


  • 118 elements have been identified
  • 82 elements occur naturally on Earth
  • 36 elements have been created by scientists
• Elements


  • gold, aluminum, lead, oxygen, carbon, sulfur
  • technetium, americium, seaborgium
• Compound


  A substance composed of atoms of two or more elements chemically united in fixed proportions
• Compounds can only be separated into their pure components (elements) by chemical means</b>
• Compounds


  • lithium fluoride
  • quartz
  • dry ice – carbon dioxide
• Molecule


  An aggregate of two or more atoms in a definite arrangement held together by chemical forces
• Types of molecules


  • Diatomic molecule - contains only two atoms
  • Polyatomic molecule - contains more than two atoms

  
• Diatomic molecules


  • H2, N2, O2, Br2, HCl, CO
• Polyatomic molecules


  • O3, H2O, NH3, CH4
• Ion


  An atom, or group of atoms, that has a net positive or negative charge
• Types of ions


  • Cation - ion with a positive charge
  • Anion - ion with a negative charge
• Monatomic ions


  • Na+, Cl-, Ca2+, O2-, Al3+, N3-
• Polyatomic ions


  • OH-, CN-, NH4+, NO3-
• The sum of the charges on the cation(s) and anion(s) in each formula unit of an ionic compound must equal zero
• The most reactive metals (green) and the most reactive nonmetals (blue) combine to form ionic compounds
• Covalent bond


  Attraction between the nucleus of the 1st atom and the electrons of the 2nd atom; and the attraction of the nucleus of the 2nd atom and the electrons of the 1st atom.

  
  

  Sharing of electrons.
• Electronegativity


  The ability of an atom to attract toward itself the electrons in a chemical bond
• Fluorine has the highest electronegativity
• Covalent compounds


  • Intermolecular forces of attraction is weak
  • Gas, liquid or low-melting point solid
  • Insoluble in H2O (mostly)
  • Aqueous solutions do not conduct electricity
• Bond energy


  The amount of energy involved when a bond is broken or formed
• Bond length


  The distance between the nuclei of atoms forming the bond
• Bond order


  The number of bonds between atoms (single, double or triple)
• Ionic bond


  Attraction between cations and anions
• Valence electrons


  The outer shell electrons of an atom that participate in chemical bonding
• Lewis dot symbols


  • Consist of the symbol of an element and 1 dot for each valence electron in an atom of the element
• Octet rule


  The tendency of atoms (representative elements) to lose, gain or share electrons in order to acquire an octet of electrons in their outermost main energy level
• Valence Shell Electron Pair Repulsion (VSEPR) Theory


  Determines the shape of molecules
• Polar molecule


  Possesses polar bonds where the two atoms have different electronegativities
• Intermolecular forces of attraction (IMFA)


  Attractive forces between molecules, versus intramolecular forces of attraction (covalent or ionic)
• Types of IMFA


  • Dipole-dipole forces
  • Ion-dipole forces
  • London dispersion forces (induced dipole forces)
  • Ion-ion forces
  • Hydrogen bonding