elements compounds and mixtures

• What is an element?

  • A substance made of only one type of atom
  • Around 100 different elements exist
  • Represented by symbols 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 defines an element in terms of its atoms?

  All of the atoms are the same
• If you combine magnesium and sulfur, what do you get?

  Magnesium sulfide
• What is a compound?

  • A substance formed from 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 a compound?

  The ratio of different elements is constant
• 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 compared to magnesium sulfide?

  Magnesium is a shiny metal, while magnesium sulfide forms white crystals
• 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 is the difference between a molecule and a compound?

  A molecule can consist of the same or different elements, while a compound has different elements
• What techniques can be used to separate a mixture?

  Filtration, distillation, crystallization, or chromatography
• What are examples of molecules that are also compounds?

  • Methane (CH₄)
  • Water (H₂O)
  • Ammonia (NH₃)
• What are examples of molecules that are not compounds?

  Chlorine (Cl₂) and oxygen (O₂)
• What is the chemical composition of methane?

  Carbon and hydrogen
• What is the chemical composition of water?

  Hydrogen and oxygen
• What is the chemical composition of ammonia?

  Nitrogen and hydrogen
• What is the significance of the periodic table in chemistry?

  It organizes all known elements and their symbols