Compounds, Molecules & Mixtures

• What are the three important terms to understand when looking at how atoms exist in the real world?

  Molecules, mixtures, and compounds
• How is a molecule defined?

  A molecule is a group of two or more atoms held together by chemical bonds
• What is an example of a molecule found in the air?

  Oxygen
• Can molecules contain multiple different elements?

  Yes, molecules can contain multiple different elements
• What is the composition of a water molecule?

  One atom of oxygen bonded to two atoms of hydrogen
• Why is helium not considered a molecule?

  Because it exists as a single atom
• What defines a compound?

  A compound contains two or more different elements held together by chemical bonds
• Why is water classified as a compound?

  Because it contains the elements hydrogen and oxygen
• What is a key feature of compounds regarding the elements involved?

  The elements are always found in the same proportions
• What is the chemical formula for water?

  H₂O
• What does the subscript in a chemical formula signify?

  It indicates the number of atoms of that element in the molecule
• What is the formula for carbon dioxide?

  CO₂
• What does the formula H₂SO₄ represent?

  Sulfuric acid
• How do brackets function in chemical formulas?

  Brackets group together elements and the number outside indicates how many of those groups there are
• What is the formula for calcium hydroxide?

  Ca(OH)₂
• What is a characteristic of large compounds like sodium chloride?

  They exist as huge structures containing millions or billions of atoms
• What is the formula for sodium chloride?

  NaCl
• How do ionic bonds affect the structure of compounds?

  Ionic bonds lead to the formation of large structures rather than small molecules
• What does the formula for sodium chloride represent?

  It acts as a ratio of sodium to chloride ions
• What is a mixture?

  A mixture consists of two or more substances that are not chemically combined
• How can you separate the components of a mixture?

  Using physical methods like filtration, crystallization, or distillation
• What are the differences between molecules, compounds, and mixtures?

  • Molecules: Groups of two or more atoms bonded together.
  • Compounds: Substances with two or more different elements bonded together.
  • Mixtures: Combinations of substances that are not chemically bonded.
• What are the key features of compounds?

  • Contain two or more different elements
  • Atoms are held together by chemical bonds
  • Elements are always in the same proportions
• What are the methods to separate mixtures?

  • Filtration
  • Crystallization
  • Distillation