Elements, Compounds, and Mixtures

• What is meant by an element in chemistry?

  An element consists of atoms that are all the same.
• How many different elements are there approximately?

  There are around 100 different elements.
• Why is the periodic table important in chemistry?

  It shows the different elements and their symbols.
• What is the symbol for magnesium?

  The symbol for magnesium is $Mg.$
• What is the symbol for sulfur?

  The symbol for sulfur is $S.$
• What defines a compound in chemistry?

  • 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 a compound?

  It means the ratio of elements in a compound is constant.
• How do the properties of compounds differ from the properties of the elements they are made from?

  Compounds usually have different properties than the elements they are made from.
• What is required to separate a compound back into its elements?

  A chemical reaction is needed to separate a compound into its elements.
• What is a mixture in chemistry?

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

  Filtration, distillation, crystallization, and chromatography can be used to separate mixtures.
• What is the difference between a molecule and a compound?

  • A molecule can consist of the same or different elements combined
  • A compound consists of different elements chemically combined
• What is a molecule that is not a compound?

  Chlorine and oxygen molecules are examples of molecules that are not compounds.
• Why might students confuse molecules with compounds?

  Because both involve elements combined, but compounds have different elements.