1.3 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
• Can molecules contain multiple different elements?

  Yes, molecules can contain multiple different elements
• How do molecules differ from compounds?

  • Molecules: Groups of two or more atoms held by chemical bonds
  • Compounds: Substances containing two or more different elements held by chemical bonds
• What is a molecule?

  A molecule is a group of two or more atoms held together by chemical bonds
• What is an example of a molecule that consists of just one element?

  Oxygen
• What is the composition of a water molecule?

  One atom of oxygen bonded to two atoms of hydrogen
• What is the formula for water?

  H₂O
• Why is carbon dioxide considered a compound?

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

  The elements are always found in the same proportions
• How is the formula for a compound written?

  Using chemical symbols and the numbers of each atom
• What does the subscript in a chemical formula signify?

  The number of atoms of that element in the molecule
• What does the formula H₂SO₄ represent?

  It represents sulfuric acid, containing two hydrogen atoms, one sulfur, and four oxygens
• What do brackets in chemical formulas indicate?

  They group together everything inside them, with the number outside indicating how many of those groups there are
• What is the formula for calcium hydroxide?

  Ca(OH)₂
• How do ionic bonds affect the structure of compounds like sodium chloride?

  Ionic bonds lead to large structures containing millions or billions of atoms
• What is the formula for sodium chloride?

  NaCl
• How can you tell which compounds will form large substances rather than molecules?

  They have ionic bonds
• What does the formula NaCl represent in terms of ratios?

  It shows a one-to-one ratio of sodium ions to chloride ions
• What are mixtures?

  Mixtures consist of two or more substances that are not chemically combined
• How can mixtures be separated?

  Using physical methods like filtration, crystallization, or distillation
• What are the characteristics of mixtures?

  • Consist of two or more substances
  • Not chemically combined
  • Can be separated by physical methods
• What happens when you mix oxygen molecules, sodium chloride, helium atoms, and carbon dioxide in a beaker?

  It creates a mixture