Chemistry

• Take Good Care of this Textbook
• This textbook is the property of your school
• 10 ideas to help take care of the book

  • Cover the book with protective material, such as plastic, old newspapers or magazines
  • Always keep the book in a clean dry place
  • Be sure your hands are clean when you use the book
  • Do not write on the cover or inside pages
  • Use a piece of paper or cardboard as a bookmark
  • Never tear or cut out any pictures or pages
  • Repair any torn pages with paste or tape
  • Pack the book carefully when you place it in your school bag
  • Handle the book with care when passing it to another person
  • When using a new book for the first time, lay it on its back. Open only a few pages at a time. Press lightly along the bound edge as you turn the pages. This will keep the cover in good condition
• Take Good Care of this CHEMISTRY TEXTBOOK GRADE 11
• Writers


  • Tsegaye Girma (PhD)
  • Abera Gure (PhD)
• Editors


  • Chala Regasa (MSc) (Content Editor)
  • Taye Hirpassa (BSc., MA) (Curriculum Editor)
  • Meseret Getnet (PhD) (Language Editor)
• Illustrator: Asresahegn Kassaye (MSc)
• Designer: Daniel Tesfay (MSc)
• Evaluators


  • Tolessa Mergo Roro (BSc., MEd)
  • Nega Gichile (BSc., MA)
  • Sefiw Melesse (MSc.)
• FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA MINISTRY OF EDUCATION
• FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA HAWASSA UNIVERSITY
• Foreword: Education and development are closely related endeavors. This is the main reason why it is said that education is the key instrument in Ethiopia's development and social transformation. The fast and globalized world we now live in requires new knowledge, skill and attitude on the part of each individual. It is with this objective in view that the curriculum, which is not only the Blueprint but also a reflection of a country's education system, must be responsive to changing conditions.
• Philosophers of ancient Greece wondered about the composition of matter: is matter continuously divisible into ever smaller and smaller pieces, or is there an ultimate limit?
• Most philosophers, including Plato and Aristotle, believed that matter is continuous, but Democritus disagreed
• Democritus


  Greek philosopher who suggested that if you divided matter into smaller and smaller pieces, you would eventually end up with tiny, indestructible particles called atomos, or "atoms", meaning "indivisible"
• Democritus' ideas were based on philosophical speculation rather than experimental evidence
• Democritus' ideas were not widely accepted until 1808, when John Dalton developed an atomic theory that had gained broad acceptance
• Postulates of Dalton's atomic theory

  • Not provided
• Postulates of the modern atomic theory

  • Not provided
• Laws of chemistry


  • Conservation of mass
  • Definite proportions
  • Multiple proportions
• The modern atomic theory is generally said to begin with John Dalton
• Dalton's work was mainly about the chemistry of atoms and how they combine to form new compounds rather than about the internal structure of atoms
• The modern theories about the physical structure of atoms did not begin until J.J. Thomson discovered the electron in 1897
• Cathode rays


  Rays that originate from the cathode and cause the glass tube to emit a greenish light
• Cathode rays


  • They move toward the anode, where some rays pass through a hole to form a beam
  • The beam bends away from the negatively charged plate and toward the positively charged plate
  • The characteristics of cathode rays are independent of the material making up the cathode

  
• Thomson concluded that a cathode ray consists of a beam of negatively charged particles (or electrons) and that electrons are constituents of all matter

  
• Radioactivity


  The spontaneous emission of particles and/or radiation from the unstable nuclei of certain atoms such as uranium, radium, etc.
• Types of radioactive radiation

  • Alpha (α) rays
  • Beta (β) rays
  • Gamma (γ) rays
• Alpha (α) rays


  • Positively charged particles, identical to helium nuclei
  • Have a mass of about four times that of a hydrogen atom
  • Have a charge twice the magnitude of an electron
• Beta (β) rays


  • Electrons coming from inside the nucleus
  • Deflected by the negatively charged plate

  
• Gamma (γ) rays


  • High-energy rays
  • Have no charge
  • Not affected by an external electric or magnetic field
• Radioactivity does not support Dalton's idea of atoms
• Three types of rays identified in the emissions from radioactive substances

  • Alpha (α) rays
  • Beta (β) rays
  • Gamma (γ) rays
• Alpha (α) rays


  • Positively charged particles, called α particles, with a mass of about four times that of a hydrogen atom and a charge twice the magnitude of an electron, identical to helium nuclei
• Beta (β) rays


  • Electrons coming from inside the nucleus, deflected by the negatively charged plate
• Gamma (γ) rays


  • High-energy rays with no charge, not affected by an external electric or magnetic field
• Thomson's "plum-pudding" model


  Atoms with electrons and protons randomly distributed in a positively charged cloud
• Rutherford's experiment


  1. Positively charged particles aimed at a thin sheet of gold foil

  2. Some particles deflected as they passed through the gold foil

  3. A few particles deflected so much that they went back in the opposite direction
• Most α-particles passed through the foil undeflected
• Only a small fraction of the α-particles showed a slight deflection