General

• What topics are covered in OCR GCSE chemistry paper one?

  Particles, elements, compounds, and chemical reactions
• What is a compound?

  A substance with two or more different atoms bonded
• How many hydrogen atoms are in one water molecule?

  Two hydrogen atoms
• What does it mean if there is no number after a chemical symbol?

  It indicates an invisible one atom
• What must be true about atoms in a chemical reaction?

  The same number of each atom must exist on both sides
• What is the first step in balancing a chemical equation?

  Start with atoms only in compounds
• What is a mixture?

  A combination of different elements and compounds
• How can you separate sand from water?

  Using filtration
• What is crystallization used for?

  To separate a solute from a solvent
• What is distillation?

  Heating a solution to separate liquids
• What is fractional distillation?

  Separating liquids with different boiling points
• Why is obtaining pure substances important in chemistry?

  To ensure accurate results in experiments
• How can you tell if a substance is pure?

  By testing its melting or boiling point
• What is a formulation in chemistry?

  • A mixture designed for a specific purpose
  • Contains specific quantities of substances
  • Examples: paints, fuels, alloys, fertilizers
• What is chromatography used for?

  To separate substances in a mixture
• What is the stationary phase in chromatography?

  Special chromatography paper or filter paper
• What is the mobile phase in chromatography?

  Water or another solvent moving up the paper
• What does the RF value represent in chromatography?

  The ratio of distance moved by substance to solvent
• What are the three main states of matter?

  Solid, liquid, and gas
• How do particles behave in a solid?

  They vibrate around fixed positions
• How do particles behave in a gas?

  They move randomly and are far apart
• What must be supplied to melt or evaporate a substance?

  Energy, usually in the form of heat
• What do state symbols indicate in chemical equations?

  The state of each substance involved
• What does the symbol (s) represent in a chemical equation?

  Solid state
• What does the symbol (l) represent in a chemical equation?

  Liquid state
• What does the symbol (g) represent in a chemical equation?

  Gas state
• What does the symbol (aq) represent in a chemical equation?

  Aqueous state, dissolved in solution
• Who discovered that atoms are made of positive and negative charges?

  JJ Thompson
• What model did JJ Thompson propose?

  The plum pudding model of the atom
• What did Ernest Rutherford discover about the nucleus?

  It is incredibly small and dense
• What did Niels Bohr discover about electrons?

  They exist in shells or orbitals
• What did James Chadwick discover?

  The existence of neutrons in the nucleus
• What is the charge of protons and electrons?

  Protons are +1, electrons are -1
• What is the relative mass of neutrons?

  One
• What does the atomic number represent?

  The number of protons in the nucleus
• What does the mass number indicate?

  The total number of protons and neutrons
• What are isotopes?

  Atoms of the same element with different neutrons
• What is relative abundance?

  The percentage of each isotope in a sample
• How is the average relative atomic mass calculated?

  By averaging the masses of isotopes
• How did Dmitri Mendeleev organize the periodic table?

  By atomic weights and properties