Science draft

• What are isotopes?

  Atoms with the same atomic number but different mass numbers
• What is a molecule?

  Two or more atoms held together by chemical bonds
• What defines a compound?

  Two or more different elements held by chemical bonds
• What are the separation techniques in chemistry?

  • Filtration
  • Evaporation
  • Crystallisation
• How is evaporation performed in a laboratory setting?

  By placing a dish near gently heated water in a water bath
• What should you do once crystals are seen during evaporation?

  Stop heating and let it cool
• What is the process after cooling in evaporation?

  Filter with paper and funnel, then dry in a warm environment
• What is simple distillation used for?

  To separate a liquid from a solution
• What happens during simple distillation?

  The mixture is heated so pressure forces it down the condenser
• What occurs to the vapor in simple distillation?

  The vapor cools and drips into a beaker
• What is fractional distillation used for?

  To separate a mixture of liquids
• What is a key feature of the fractionating column in fractional distillation?

  It has glass rods for high surface area and is cooler at the top
• Who proposed the first atomic model and what was it called?

  • John Dalton proposed the sphere model
• What was J.J. Thompson's contribution to atomic theory?

  • Proposed the plum pudding model in 1899, introducing electrons
• What did Rutherford's experiment with alpha particles demonstrate?

  That Thompson's model was incorrect and led to the nuclear model
• What did Bohr contribute to atomic theory?

  He proposed the concept of orbits for electrons
• How did Mendeleev organize the periodic table?

  By atomic number and grouping elements with similar properties
• What are the general properties of metals?

  • Form positive ions
  • More reactive at the bottom of the table
  • Strong metallic bonds
  • Conductors of electricity
  • High melting and boiling points
  • Shiny and sonorous
• What are the general properties of non-metals?

  • Low boiling and melting points
  • Dull appearance
  • Brittle
  • Low density
• What are the characteristics of transition metals?

  • Can form more than one ion
  • Very good catalysts
• What happens to the melting and boiling points of Group 1 alkali metals as you go down the group?

  They decrease
• Why are Group 1 alkali metals highly reactive?

  Because they easily lose their outer electron
• What are halogens?

  Group of elements that form diatomic molecules
• What happens to the reactivity of halogens as you go down the group?

  Reactivity decreases
• What are noble gases known for?

  Being inert and non-flammable
• What happens to the boiling points of noble gases as you go down the group?

  They increase
• What is the hydroxide ion formula?


  OH-
• What is the nitrate ion formula?

  NO₃
• What is the carbonate ion formula?


  CO₃^{2-}
• What is the significance of ammonium ions in chemistry?

  They are a common ion in various chemical reactions
• What are the properties of metallic bonding?

  • High melting and boiling points
  • Conduct electricity and heat
  • Regular pattern due to delocalised electrons
• What is the structure of alloys?

  • Mixture of different elements
  • Different size atoms prevent layers from sliding
  • Makes alloys harder than pure metals
• What defines an acid in chemistry?

  A substance that forms an aqueous solution with a pH less than 7
• What defines a base in chemistry?

  A substance with a pH greater than 7
• What is a strong acid?

  An acid that completely ionizes in solution
• What is a weak acid?

  An acid that partially ionizes in solution
• What is the general reaction between a metal and an acid?

  Metal + Acid → Salt + Water
• What is the general reaction between a metal hydroxide and an acid?

  Metal Hydroxide + Acid → Salt + Water
• What is the general reaction between an acid and a metal carbonate?

  Acid + Metal Carbonate → Salt + Water + CO₂
• What is a redox reaction?

  A reaction involving both oxidation and reduction