Elements,compounds,and Mixtures

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

  Elements, compounds, mixtures, and molecules
• What is the definition of an element?

  • All atoms in an element are the same
  • Represented by symbols in the periodic table
  • Example: Magnesium and sulfur are elements
• 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 is a compound?

  • A substance formed when two or more different elements are chemically combined
  • Contains elements in fixed proportions
  • Example: Magnesium sulfide
• What does "fixed proportions" mean in a compound?

  The ratio of different atoms in the compound is constant
• What is the proportion of magnesium to sulfur in magnesium sulfide?

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

  Compounds usually have different properties than their constituent elements
• What is an example of a compound and its properties?

  Magnesium is a shiny metal, sulfur is a yellow solid, but magnesium sulfide forms white crystals
• How can a compound be separated back into its elements?

  By using a chemical reaction
• What is a mixture?

  • Contains different elements or compounds that are not chemically combined
  • Example: A mixture of magnesium atoms, sulfur atoms, and magnesium sulfide
  • Can be separated using physical techniques
• What techniques can be used to separate a mixture?

  Filtration, distillation, crystallization, or chromatography
• What is the difference between a molecule and a compound?

  • A molecule can consist of the same or different elements chemically combined
  • A compound consists of different elements chemically combined
  • Examples: Methane, water, and ammonia are compounds; chlorine and oxygen are molecules but not compounds
• 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 composed of?

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

  Two oxygen atoms chemically combined