Chemistry: Elements and Purity Measures
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Questions and Answers

What does 24 carat gold signify?

  • 92.5% pure gold
  • Pure gold (100% purity) (correct)
  • 75% gold, 25% other metals
  • 50% gold, 50% other metals
  • Seawater is primarily composed of salts, making up 96.5% of its composition.

    False (B)

    What element are pure diamonds made of?

    Carbon

    Silver marked '925' indicates that it is ______% pure silver.

    <p>92.5</p> Signup and view all the answers

    Match the carat of gold with the percentage of gold content:

    <p>24 Carat Gold = 100% Gold 18 Carat Gold = 75% Gold 9 Carat Gold = Lower percentage of Gold</p> Signup and view all the answers

    Which salt makes up the largest percentage of the salt content in seawater?

    <p>Sodium chloride (D)</p> Signup and view all the answers

    Pure products in chemistry always involve multiple reactants and multiple products.

    <p>False (B)</p> Signup and view all the answers

    Why is it important to use pure products in medicine and food production?

    <p>To ensure effectiveness and prevent harmful side-effects.</p> Signup and view all the answers

    Flashcards

    Pure Element

    A substance consisting of only one type of atom, like gold or carbon.

    Gold Purity Measurement

    Gold purity is measured in carats. 24 carats means 100% pure.

    Carat Values

    18 carat gold is 75% gold and 9 carat is lower purity.

    Silver Purity Measurement

    Silver purity is measured in parts per thousand, marked like 925.

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    Diamond Composition

    Pure diamonds are made entirely of carbon atoms and are colorless.

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    Seawater Composition

    Seawater is 96.5% water and 3.5% dissolved salts, mainly sodium chloride.

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    Importance of Seawater

    Seawater provides salt, supports ecosystems, and can be desalinated for fresh water.

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    Pure Products in Chemistry

    Substances without impurities, can be single or multiple product reactions.

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    Study Notes

    Pure Elements

    • A pure element is made up of only one type of atom
    • Example: Gold is made up of only gold atoms

    Gold Purity

    • Gold purity is measured in carats
    • 24 carat gold: Pure gold (100% purity)
    • 18 carat gold: 75% gold, 25% other metals
    • 9 carat gold: Lower purity with more alloy metals

    Silver Purity

    • Silver purity is measured in parts per thousand
    • Marked 925: 92.5% pure silver
    • Marked 900: 90% pure silver
    • Higher the number, greater the purity

    Diamonds and Their Purity

    • Pure diamonds are made entirely of carbon atoms and are colorless
    • Colored diamonds form when other elements mix with carbon
      • Yellow: Nitrogen replaces some carbon atoms
      • Blue: Boron replaces some carbon atoms
      • Green: Rare, caused by nitrogen, nickel, or hydrogen impurities
    • Diamonds are made from carbon atoms arranged in a specific structure
    • Pure diamonds contain only carbon atoms and are colorless and translucent

    Seawater: Composition and Properties

    • Seawater is a mixture of water and dissolved salts
    • Water makes up 96.5% of seawater
    • Salts make up 3.5%, primarily sodium chloride
    • Seawater can be processed to extract salt by evaporation
    • The salt content in seawater consists of:
      • Sodium chloride: 68%
      • Magnesium chloride: 14.6%
      • Sodium sulfate: 11.4%
      • Calcium chloride: 3.1%
      • Other salts: 2.9%
    • Importance of Seawater:
      • Provides salt for consumption and industry
      • Essential for marine ecosystems
      • Can be processed for fresh water through desalination

    Pure Products in Chemistry

    • Pure products in chemistry are substances without impurities
    • Example of a single product reaction:
      • Magnesium + Oxygen → Magnesium Oxide
    • Example of multiple product reactions:
      • Silver nitrate + Sodium chloride → Sodium nitrate + Silver chloride

    Importance and Safety Measures

    • Importance:
      • Ensures effectiveness in medicine and food products
      • Prevents harmful side effects due to impurities
    • Safety Measures:
      • Always wear safety glasses
      • Handle chemicals with care

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    Pure Elements Grade 8 PDF

    Description

    This quiz explores the concepts of pure elements, gold and silver purity measurements, and the characteristics of diamonds. Test your knowledge of how these substances are defined and classified based on their purity. Understand the implications of purity in various materials.

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