Commonly asked questions

• Isotopes

  An atom with the same number of protons but different number of neutrons
• Increasing temperature increases reaction rate

  1. Particles move faster and have more energy

  2. More collisions per second so greater collision rate

  3. More of the colliding molecules/particles have sufficient energy (activation energy) to react
• Decreasing temperature decreases reaction rate


  1. Particles have less energy and move slower

  2. Fewer collisions per second so smaller rate of collision

  3. Fewer portion of particles have sufficient energy to react
• Characteristics of Aluminium

  • Ductile/malleable
  • Conducts electricity
  • Low density
  • Protective oxide layer
• Saturated solution


  A solution that can dissolve no more solute at the particular/specific/any given temperature
• Why does temperature not increase while melting or boiling

  
  

  because energy is used to break bonds/overcome attraction between molecules
• Cotton wool in experiment

  • Allows gas to escape
  • Prevents loss of acid
• Graph levels off because reaction is finished and all the nitric acid is used up
• Metals


  • Lattice of positive ions/cations
  • Delocalised/sea of electrons
  • Attraction between positive and negative
• Atom has overall charge 0


  Same number of protons and electrons
• Ion has charge of X+

  X more protons than electrons
• Ion has charge of X-

  X less protons than electrons
• Lumps vs powder


  • Lumps have smaller surface area and fewer collisions per unit time
  • Powder has larger surface area and more collisions per unit time
• Observations when sodium reacts with water

  • Fizz/bubbles
  • Moves
  • Floats
  • Melts/forms a ball
  • Gets smaller/disappears
• Gases diffuse


  Due to random motion of molecules/particles from the region of higher concentration to lower concentration
• Element found in clean dry air is Argon
• Compound found in clean dry air is Carbon dioxide
• Solid is added in excess to an acid to make sure all the acid reacts
• If excess calcium metal is added to dilute hydrochloric acid instead of excess zinc powder, pure calcium chloride crystals do not form because Ca will also react with water
• Checking if all water has been given off from a hydrated salt

  Heat again and weigh again and repeat until mass is constant
• Exothermic reaction


  More energy released (in bond formation) than used/taken in (in bond breaking)
• Process used to separate the products of hydrolysis of long chain carbohydrates is Chromatography
• Oxides of nitrogen form in a car engine


  Nitrogen and oxygen (from the air) react (in the engine) due to high temperatures
• Catalyst used in catalytic converter is platinum
• Catalyst


  A substance which increases the rate of a reaction, remains unchanged/unaffected/unused or without changing mass
• From the first 30 elements, the gas that diffuses with the slowest rate is Chlorine
• Decreasing rate of reaction over time

  Concentration of particles decreases, lower rate of collisions of particles
• Effects of nitrogen dioxide

  • Respiratory problems
  • Acid rain
• Redox


  Reduction and oxidation occurs simultaneously
• Gas used to convert iron to steel is Oxygen
• Solid sodium conducts electricity

  Electrons move/are mobile/flow
• Molten sodium chloride conducts electricity


  Ions move/are mobile/flow
• Deciding suitable number of results

  At least two results are within 0.2 cm3 or less
• Increasing surface area


  Rate of reaction increases, more collisions per unit time
• When group 1 element reacts with cold water, a metal hydroxide is formed
• Indication that copper(II) oxide is in excess is that undissolved solid remains
• Oxidising agent


  It has gained electrons hence reduced
• Reducing agent


  It has lost electrons hence oxidised
• The colour of bromine is Orange-Brown
• Substances that decompose to give metal oxide


  • Metal hydroxides
  • Metal carbonates
  • Metal nitrates