Elements, Compounds and Mixtures

• What happens when atoms of magnesium and sulfur are combined?

  They form a compound called magnesium sulfide
• What is a compound?

  Two or more different elements chemically combined
• What does "fixed proportions" mean in a compound?

  Elements are combined in a specific ratio
• What is the appearance of magnesium and sulfur?

  Magnesium is shiny, sulfur is yellow
• What do magnesium sulfide crystals look like?

  They form white crystals
• How can a compound be separated back into its elements?

  Using a chemical reaction
• What is a mixture?

  Different elements or compounds not chemically combined
• How can mixtures be separated?

  Using physical separation techniques
• Name some physical separation techniques.

  Filtration, distillation, crystallization, chromatography
• What is a molecule?

  Elements chemically combined, even if the same
• What elements are contained in methane?

  Carbon and hydrogen
• What elements are contained in water?

  Hydrogen and oxygen
• What elements are contained in ammonia?

  Nitrogen and hydrogen
• What is a chlorine molecule?

  Two chlorine atoms chemically combined
• What is an oxygen molecule?

  Two oxygen atoms chemically combined
• What are the differences between compounds and mixtures?

  • Compounds:
  • Chemically combined
  • Fixed proportions
  • Different properties from elements
  • Mixtures:
  • Not chemically combined
  • Can be separated physically