Ancient Philosophers on Matter
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Questions and Answers

Which of the following statements accurately reflects John Dalton's atomic theory?

  • All elements are composed of compounds made up of multiple identical atoms.
  • Atoms of different elements can be created from one another through chemical reactions.
  • Atoms are the smallest units of matter and can be divided into smaller particles.
  • Atoms of a given element are identical in mass and size, differing from other elements. (correct)
  • What did Empedocles propose was the composition of all matter?

  • Four fundamental elements: earth, fire, air, and water. (correct)
  • A combination of atoms and electrons.
  • Atoms that can be divided further into smaller units.
  • Invisible particles he termed 'elementos'.
  • Which philosopher's ideas led to the decline of the atomic view of matter for centuries?

  • Democritus
  • G.C.E. Stoney
  • John Dalton
  • Aristotle (correct)
  • What scientific device did Sir William Crookes invent to study electrical discharge?

    <p>Crookes tube or cathode ray tube</p> Signup and view all the answers

    What term did Johnstone G. Stoney use to describe the fundamental unit carrying electricity?

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

    What significant value did J.J. Thomson calculate regarding cathode rays?

    <p>1.76 x 10^8 coulombs per gram for the ratio of the electron's charge to its mass</p> Signup and view all the answers

    Which property indicates that cathode rays possess kinetic energy?

    <p>They rotate a light paddle wheel placed in their path.</p> Signup and view all the answers

    What happens when an electric field is applied to cathode rays?

    <p>They are deflected towards the positively charged plate.</p> Signup and view all the answers

    What was a common misconception about the nature of cathode rays during J.J. Thomson's time?

    <p>They were thought to be waves of light.</p> Signup and view all the answers

    Which experimental result supported the particle theory of cathode rays?

    <p>The formation of a shadow when obstructed.</p> Signup and view all the answers

    Study Notes

    Ancient Philosophical Views on Matter

    • Early speculations about fundamental components of the world date back to philosophers such as Empedocles (~440 BC), who proposed four elements: earth, fire, air, and water.
    • Hindus similarly recognized these four elements as constitutive of the universe and space.
    • Democritus (460–370 BC) introduced the concept of ‘atomos’, envisioning the material world as composed of tiny, indivisible particles.

    Shift in Philosophical Thought

    • Plato and Aristotle dismissed the idea of indivisible particles, leading to the decline of atomic theory during the dominance of Aristotelean philosophy for centuries.

    Dalton's Atomic Theory

    • In 1808, John Dalton articulated a clear definition of atoms, asserting:
      • Elements consist of extremely small, indivisible particles known as atoms.
      • All atoms of a given element are identical in mass and size, differing from atoms of other elements.
      • Atoms of one element cannot convert into atoms of another element through chemical reactions; atoms are conserved in reactions.
      • Compounds form through the union of two or more atoms from different elements in simple numerical ratios.
    • Dalton's model is referred to as the "Golf ball model."

    Discovery of Electrons

    • Johnstone G. Stoney (1826-1911) coined the term “electrons” in 1891, although lacking experimental evidence.

    Cathode Ray Experimentation

    • Sir William Crookes invented the cathode ray tube in the mid-1800s to investigate electrical discharge in a vacuum.
    • When high voltage is applied, the cathode (negatively charged plate) emits a stream of unseen radiation known as cathode rays, causing low-pressure gases to glow.

    Properties of Cathode Rays

    • Cathode rays travel in straight lines, as proven by the formation of sharp-edged shadows when opaque objects obstruct their path.
    • They exhibit mass and possess kinetic energy; a light paddle wheel placed in their path will rotate, indicating momentum (though heating effects might influence this).
    • Application of an electric field results in the deflection of cathode rays toward positive plates, confirming their negative charge. Their trajectory in a magnetic field aligns with that of other negatively charged particles.

    J.J. Thomson's Contributions

    • J.J. Thomson (1856–1940) established that cathode rays are identical regardless of the cathode material and gas used in the tube.
    • In 1897, he described cathode rays as streams of negatively charged particles and calculated the electron's charge-to-mass ratio at 1.76 x 10^8 coulombs per gram.

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    Description

    Explore the ideas of early philosophers like Empedocles and Democritus, who significantly contributed to our understanding of the fundamental components of the world. This quiz delves into their beliefs regarding the elements and the concept of atoms, comparing Eastern and Western philosophies on matter.

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