Elements, Compounds and Mixtures

• What is an element?

  • A substance made of only one type of atom
  • Around 100 different elements exist
  • Represented in the periodic table
• How many different elements are there approximately?

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

  A different element
• What is the symbol for magnesium?

  Mg
• What is the symbol for sulfur?

  S
• What is the definition of an element?

  • All atoms in an element are the same
  • Example: All magnesium atoms are identical
  • Example: All sulfur atoms are identical
• 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 from the elements it is made from
• What does "fixed proportions" mean in the context of compounds?

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

  1. 1
• How do the properties of compounds compare to the elements they are made from?

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

  Magnesium is a shiny metal, sulfur is a yellow solid
• What is required to separate a compound back into its elements?

  A chemical reaction
• What is a mixture?

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

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

  • Any elements chemically combined
  • Can be the same or different elements
  • Examples include methane, water, and ammonia
• How does a molecule differ from a compound?

  A molecule can consist of the same element, while a compound has different elements
• 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
• Are chlorine and oxygen molecules compounds?

  No, they are molecules but not compounds
• 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
• What resources can help with revision on this topic?

  • Revision workbook available through a link
  • Additional resources may be provided in future videos