Diff between Compounds, Molecules and Mixtures

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

  Molecules, mixtures, and compounds
• How do molecules differ from compounds?

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


  A molecule is a group of two or more atoms that are held together by chemical bonds.
• Can molecules contain multiple different elements? Give an example.

  Yes, for example, water molecules contain one atom of oxygen and two atoms of hydrogen.
• What is an example of a molecule that consists of just one element?

  Helium
• What defines a compound?

  A compound is a substance that contains two or more different elements.
• Why are molecules like oxygen, chlorine, and nitrogen not considered compounds?

  Because they only contain one type of element.
• What is a key feature of compounds regarding the elements involved?

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

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


  The subscript 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, which contains two hydrogen atoms, one sulfur atom, and four oxygen atoms.
• How do brackets in chemical formulas function?

  Brackets group together everything inside them, 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 compounds like sodium chloride?

  They can contain millions or billions of atoms and exist as large structures.
• What is the formula for sodium chloride?

  NaCl
• Why does sodium chloride exist as large structures rather than small molecules?

  Because the bonds between the atoms are ionic bonds.
• How can we interpret the formula for sodium chloride in terms of ratios?

  The formula NaCl indicates a one-to-one ratio of sodium ions to chloride ions.
• What are mixtures and how do they differ from compounds?

  • Mixtures: Consist of two or more substances that are not chemically combined.
  • Differences: Mixtures can be separated by physical methods, while compounds cannot.
• What is an example of a mixture?

  A beaker containing oxygen molecules, sodium chloride, individual helium atoms, and carbon dioxide.
• How can mixtures be separated?

  Using physical methods like filtration, crystallization, or distillation.
• What is the main characteristic of the substances in a mixture?

  They have not reacted with each other and have no chemical bonds between them.