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Chemistry - Elements and Compounds

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Chemistry - Elements and Compounds Chemistry - Elements and Compounds Presentation Transcript

  • Elements and Compounds
  • Elementary…
    • “ Elementary, my dear Watson.”
    • Fundamentals or basics
  • An Ancient Definition
    • Aristotle first classified matter as “elements”.
    • “ one of those bodies into which other bodies can be decomposed and which itself is not capable of being divided into other”
  • Elements
    • Substances can be considered elements or compounds
    • An element is the simplest form of matter that has a unique set of properties.
    • All substances found on periodic table are elements.
  • Compounds
    • A compound is a substance that contains two or more elements bonded together
    • Can be broken down into simpler substances by CHEMICAL means (elements cannot)
  • Compounds
    • Breaking down compounds must involve a chemical change.
    • Dissolving salt – Physical
    • Boil water – Physical
    • Heat sucrose - CHEMICAL
  • Properties of Compounds
    • Properties of compounds are usually different from their component elements
    • Ex.  Sodium is an explosive metal. Chlorine is a toxic, green gas. Sodium chloride is table salt.
  • Matter Substances Mixtures Elements Compounds Homogeneous Mixtures Heterogeneous Mixtures
  • Symbols and Formulas
    • One- and two-letter symbols used to identify elements
    • Chemical formulas used to identify compounds
    • Many elemental symbols reference the element’s LATIN name.
  • More Information on Chemical Changes
  • Chemical Changes
    • Also called chemical reactions
    • During a chemical change, compounds can be formed, broken down, or both
  • Chemical Reactions
    • Starting substances are called REACTANTS
    • Ending substances are called PRODUCTS
  • Chemical Reactions
    • Can result in formations of solids, liquids, or gases
    • Precipitate – solid that forms within a liquid and settles out
  • Law of Conservation of Mass
  • Law of Conservation of Mass
    • During any chemical reaction, the mass of the products is always equal to the mass of the reactants.
    • Therefore, matter is neither created nor destroyed during a chemical reaction, only changed.
  • Questions to Think About
    • Each group should answer all 7 questions.
    • Questions should be answered neatly and completely. Your participation will be factored into your quarter grade.
    • Physical Change or Chemical Change?
      • Dissolving sugar in iced tea
      • A bicycle rusting on the lawn
      • Scrambling an egg
      • Cooking the egg
      • Recycling plastic bottles into plastic benches
      • Burning plastics for energy
    • “ Fools gold” is a compound known as pyrite (iron and sulfur). When completely broken down, a 45.2-g sample yields 21.0 g of iron. How much sulfur is produced? Explain.
    • Explain this statement: “A gas requires a container but a solid is its own container.
    • Propose a multi-step solution to separating the following mixture: iron filings, sand, salt, cooking oil, and water.
    • Explain why this statement is false. Give examples. “Because there is no change in composition during a physical change, the appearance of the substance will not change.”
    • Every day you encounter chemical changes that are harmful and that are helpful to humans or the environment. Name at least two of each. Also, write how you KNOW that it is a chemical change.
    • Explain why some reactions may not SEEM, at first, like they follow the Law of Conservation of Mass.