Atomic structure and the periodic table

• What is an element composed of?

  One type of atom
• What defines a compound?

  Contains two or more different atoms joined
• How are mixtures characterized?

  Elements or compounds not chemically joined
• What is the structure of compounds?

  Regular structure with fixed composition
• What must be used to separate components in a compound?

  Chemical reactions
• How do mixtures differ from compounds in structure?

  Mixtures have no regular structures
• How can components of a mixture be separated?

  By physical means using properties
• What is a pure substance?

  Made up of one compound or element
• What are fixed points in pure substances?

  Specific melting and boiling temperatures
• How does the purity of a substance affect its melting point?

  Purer substances have smaller melting ranges
• What is a quick test for purity?

  Finding melting or boiling point
• What are examples of impure substances?

  Bottled water, honey, tea tree oil
• What are examples of pure substances?

  Elements and gold
• What is a formulation?

  • A mixture designed for a specific purpose
  • Contains carefully measured quantities of substances
  • Examples: medicine, paints, fuels
• What is the first step in testing for hydrogen?

  Add hydrochloric acid to a test tube
• What is the result of the hydrogen test?

  A squeaky pop sound
• What is the first step in testing for oxygen?

  Add hydrogen peroxide and manganese dioxide
• What happens to the glowing splint in the oxygen test?

  It reignites
• What is the first step in testing for carbon dioxide?

  Fill a test tube with limewater
• What is the result of the carbon dioxide test?

  Limewater goes cloudy white
• What is the first step in testing for chlorine?

  Hold damp litmus paper over boiling tube
• What happens to damp blue litmus paper in chlorine test?

  Turns red then white
• What is the process of paper chromatography?

  1. Draw a start line on chromatography paper
  2. Apply samples on the start line
  3. Place paper in solvent
  4. Allow solvent to rise and separate substances
  5. Mark solvent front and dry paper
• What is the purpose of calculating Rf values?

  To identify compounds based on distance
• How is the Rf value calculated?

  Distance moved by compound / distance moved by solvent
• What does a pure compound produce in chromatography?

  A singular spot in all solvents
• What are the phases involved in chromatography?

  • Stationary phase: solid or liquid on solid
  • Mobile phase: liquid solvent
• How does the mobile phase affect chromatography?

  It carries components of the mixture
• What is filtration used for?

  To separate mixtures
• How does filtration separate sand and water?

  Water passes through filter paper
• What is crystallization used for?

  • To separate a soluble substance from a solution
  • Involves evaporation and cooling
• What is the first step in simple distillation?

  Heat the solution to evaporate water
• What happens to water vapor in distillation?

  It condenses in the condenser
• What is fractional distillation used for?

  • To separate more volatile liquids
  • Involves a temperature gradient
• How does fractional distillation separate liquids?

  Based on boiling points of compounds
• What is crude oil?

  A mixture of different compounds
• How is crude oil processed?

  Heated in a fractionating tower
• What happens to the fractions in crude oil distillation?

  They condense at different temperatures
• What is the history of the atomic model?

  • Early philosophers: atoms as tiny spheres
  • John Dalton: first atomic model in 1805
  • J.J. Thompson: plum pudding model in 1890
• What did John Dalton propose about atoms?

  Atoms are tiny particles making up elements