Tuesday, July 27, 2010

Chemistry Form 4 Definition List

Chemistry Form 4 Definition List

  1. Element – a substance consists of one type of atom.
  2. Compound – a substance consists two or more elements that are chemically bonded (molecule or ions).
  3. Atomsmallest particle of an element.
  4. Molecule – a group of two or more atoms.
  5. Ion – a positively charged / negatively charged particle.
  6. Isotopes – atoms of the same element with same proton number but different nucleon numbers.
  7. Relative atomic mass of an element = the average mass of one atom of an element/((1/12) x the mass of one carbon-12 atom)
  8. Relative molecular mass of an element = the average mass of one atom of an molecule/((1/12) x the mass of one carbon-12 atom)
  9. Molecule formula – compound shows the actual number of atoms of each element that are present in a molecule of the compound
  10. Empirical formula – compound shows the simplest whole number ratio of atoms of each element in the compound
  11. Mole amount of substance that contains as many particles as the number of atoms in exactly 12 g of carbon-12 the symbol of mole is mol.
  12. One mole – Avogadro constant – 6.02 x 1023
  13. Group (Periodic Table) – vertical columns of element (similar chemical properties).
  14. Periods (Periodic Table) – horizontal rows of element.
  15. Valence electrons – electrons that occupy the outermost shell.
  16. Ionic bond – bond formed through the transfer of electrons between atoms of metal and non-metal to achieve the stable octet electron arrangement.
  17. Ionic compound – consist of positive ions and negative ions which are held by strong electrostatic forces of attraction.
  18. Covalent bond – bond formed through the sharing of non-metal electrons to achieve the stable duplet or octet electron arrangement.
  19. Covalent compound (also simple molecular structure) – consists of neutral molecules which are held by weak intermolecular forces (Van der Waals).
  20. Alkali (base) – chemical substance which ionizes in water to produce hydroxide ions, OH-.
  21. Acid – chemical substance which ionizes in water to produce hydrogen ions, H+ or hydroxonium ions, H3O+.
  22. pH – degree of acidity or alkalinity of a solution. Scale ranges from 0 to 14.
  23. pH value – measure of the concentration of hydrogen ions, H+.
  24. Strong alkali – ionises (dissociates) completely in water to form hydroxide ions, OH- of high concentration.
  25. Weak alkali – ionises (dissociates) partially in water to form hydroxide ions, OH- of low concentration.
  26. Strong acid – ionises (dissociates) completely in water to form hydrogen ions, H+ of high concentration.
  27. Weak acid – ionises (dissociates) partially in water to form hydrogen ions, H+ of low concentration.
  28. Polymer – long chain molecules made up by monomer (repeating unit).

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