Cambridge IGCS Chemistry Coursebook 2015 Chapter 2 知识点整理

物质的本质是指物质所固有的根本属性，包括其组成、结构、性质以及变化规律。在物理学、化学、生物学等多个学科领域，科学家们都对物质的本质进行了深入的研究和探讨。

The nature of matter

• Atoms and molecules
  • elements and compounds
    • elements
    • compounds
  • chemical reactions and physical changes
    • decomposition, synthsis
    • chemical reaction
      • new chemical substances are formed
      • usually the process is not easily reversed
      • energy is often given out
    • physical change
  • atomic theory
    • a chemical language
      • symbol
  • the kinetic model of matter
    • lattices
      • Solid: • packed close together • in a regular arrangement or lattice • not able to move freely, but simply vibrate in their fixed positions.
      • Liquid • closely packed together • in an irregular arrangement • able to move around past each other.
      • Gas • arranged totally irregularly • spread very far apart compared to solids and iquids • able to move randomly.
  • diffusion in fluids
    • the dissolving of gases
      • Brownian motion.
  • atoms and molecules
    • elements
• The structure of the atom
  • atomic stucture
    • subatomic particles
      • protons
      • neutrons
      • electrons
    • measuring the size of atoms
      • mass spectrometer
      • relative atomic mass
        • carbon-12
  • subatomic particles
    • Protons and neutrons have almost the same mass. Electrons have virtually no mass at all ( 1/1840 of the mass of a proton).
  • proton (atomic) number and nucleon number
    • proton number : Z
    • nucleon number : A
      • =number of protons + number of neutrons
  • isotopes
    • The number of neutrons in the atoms is the difference between isotopes. They have the same number of protons and electrons.
    • radioisotopes
  • relative atomic masses
    • 1 atomic mass unit (a.m.u.) = 1/12 × mass of one atom of carbon-12.
  • the uses of radioactivity
    • radioactive dating
      • half-life
    • industrial uses of radioisotopes
      • Major : nuclear power stations
      • Other : monitoring the level of filling in containers, checking the thickness of sheets of plastic, paper or metal foil (for example, aluminium baking foil) during continuous production, and detecting leaks in gas or oil pipes
    • medical and food-safety uses of radioisotopes
      • chemotherapy
      • radiotherapy
• Electron arrangements in atoms
  • energy levels
    • Bohr's theory
      • ◆ Electrons are in orbit around the central nucleus of the atom.
      • ◆ The electron orbits are called shells (or energy levels) and have different energies.
      • ◆ Shells which are further from the nucleus have higher energies.
      • ◆ The shells are filled starting with the one with lowest energy (closest to the nucleus).
      • ◆ The first shell can hold only 2 electrons.
      • ◆ The second and subsequent shells can hold 8 electrons to give a stable (noble gas) arrangement of electrons.
• The states of matter
  • solid, liquid, gas
  • changes in physical state
    • melting and freezing
      • melting point freezing point
    • sublimation
    • evaporation, boiling and condensation
  • pure substance
    • the effect of impurities
    • heating and cooling curves
  • types of mixture
    • solution
• Separating and purifying substance
  • separating insoluble solids from liquids
    • decanting
    • filtration
  • separating immiscible liquids
  • separating mixtures of solids
    • separations based on differences in density
    • separations based on magnetic properties
    • separations based on differences in solubility
    • separations based on sublimation
  • separating solutions
    • distillation
      • fractionating column
    • chromatogrtaohy
  • the purity and identity of substances
  • a closer look at solutions
    • the solubility of solids in liquids
      • solution
        • solute
        • solvent
      • solubility
        • saturated solution
    • the solubility of gases in liquids