1.1.2 Defining elements and compounds

• What is the chemical symbol for gold?

  Au
• Why can't you break down an element into simpler substances?

  It alters the identity of the element
• What is the chemical symbol for oxygen?

  O₂
• How can you visualize an element?

  Like tiny Lego blocks that are the same
• How do oxygen atoms exist in nature?

  They come in pairs as O₂ molecules
• How are elements in a compound combined?

  They are chemically combined
• What is a compound?

  A substance made of two or more elements
• What is the difference between an element and a compound?

  An element is a pure substance made of only one type of atom, while a compound is a pure substance made of two or more types of atoms
• What are the key differences between elements and compounds?

  • Elements are made of one type of atom
  • Compounds are made of two or more elements
  • Elements cannot be broken down without chemical reaction
  • Compounds can be broken down into elements
• What elements make up water?

  Hydrogen and oxygen
• How many types of atoms are in an element?

  One type of atom
• What are the basic units of elements and compounds?

  • Elements: Atoms
  • Compounds: Molecules
• What is the definition of a pure substance?

  An element or a compound
• What are the characteristics of a homogeneous mixture?

  • Uniform composition throughout
  • Cannot be separated by physical means
  • Appears as a single phase
• What are the characteristics of a heterogeneous mixture?

  • Non-uniform composition
  • Can be separated by physical means
  • Appears as multiple phases
• What is an element?

  A substance made of one type of atom
• What happens if you try to break down an element?

  You change what the element is
• Why can't elements in a compound be easily separated?

  They require a chemical reaction to separate
• What is a pure substance?

  An element or a compound
• How can you separate the components of a heterogeneous mixture?

  • Physical separation methods such as:
  • Filtration
  • Distillation
  • Chromatography
• Can elements be broken down without a reaction?

  No, it is not possible
• How do the compositions of homogeneous and heterogeneous mixtures differ?

  Homogeneous mixtures have a uniform composition, while heterogeneous mixtures have a non-uniform composition
• What is the composition of a compound?

  Two or more elements joined by chemical bonds
• How do elements and compounds differ in terms of particle composition?

  • Elements: Contain only one type of particle
  • Compounds: Contain two or more different atoms bonded together
• Can compounds be broken down into elements?

  Yes, they can break into elements
• What is the key difference between elements and compounds?

  Their composition