Elements, compounds and Mixtures

• What should you be able to describe by the end of this video?

  Elements, compounds, mixtures, and molecules
• Why are the concepts of elements, compounds, mixtures, and molecules important?


  They are essential in chemistry
• What is an element?

  • A substance with all atoms the same
  • Around 100 different elements exist
  • Represented in the periodic table
• How many different elements are there approximately?

  Around 100 different elements
• What does each symbol in the periodic table represent?

  A different element
• What is the symbol for magnesium?

  Capital M followed by lowercase g
• What is the symbol for sulfur?

  Capital S
• What defines an element?

  • All atoms in an element are the same
  • Examples: Magnesium and sulfur
• What happens when atoms of magnesium and sulfur are chemically combined?

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

  • Contains two or more different elements
  • Chemically combined in fixed proportions
  • Has different properties than its elements
• What does "fixed proportions" mean in a compound?

  Elements are combined in a specific ratio
• What is the proportion of magnesium to sulfur in magnesium sulfide?

  One atom of magnesium to one atom of sulfur
• How do the properties of compounds compare to their constituent elements?

  Compounds usually have different properties
• What is the appearance of magnesium and sulfur compared to magnesium sulfide?

  Magnesium is shiny, sulfur is yellow, sulfide is white
• How can a compound be separated back into its elements?

  By using a chemical reaction
• What is a mixture?

  • Contains different elements or compounds
  • Not chemically combined
  • Can be separated by physical techniques
• What techniques can be used to separate a mixture?

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

  • Elements chemically combined
  • Can be the same or different elements
• How does a molecule differ from a compound?

  A molecule can have the same elements combined
• 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 the composition of a chlorine molecule?

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

  Two oxygen atoms chemically combined
• Where can you find questions on this topic?

  • In the revision workbook
  • Available through a link provided