Chemistry STOPPED AT Salts

• Acids have more H+ ions than OH- ions, resulting in lower pH values (less than 7).
• SI unit for time is second (s).
• SI unit for temperature is kelvin (K).
• SI unit for length is metre (m).
• SI unit for mass is kilogram (kg).
• SI unit for volume is cubic metre (m3)
• Accuracy of a digital stopwatch is ± 0.01s.
• Accuracy of an analogue stopwatch is ± 0.1s.
• 1m= 10dm = 100cm = 1000mm
• A pipette measures accurate fixed volumes. (eg 10.0 cm3 or 25.0 cm3) Values read from a pipette are recorded to the nearest 0.1 cm3.
• A volumetric flask measures accurate fixed volumes that are larger. (eg 100 cm3 or 250 cm3) Values read from a volumetric flask are recorded to the nearest 1 cm3.
• A measuring cylinder measures a range of volumes to the nearest 0.5 cm3. (eg 31.5 cm3 or 23.0 cm3)
• A burette measures a range of volumes to nearest 0.05 cm3 (eg 31.55 cm3 or 23.00 cm3)
• A gas syringe is used to measure the volume of a gas. (SI unit: cm3) Values read from a gas syringe are recorded to the nearest 1 cm3.
• Water displacement is used for gases that are insoluble to slightly soluble in water. Density doesn't affect gas collection.
• Downward delivery is used to collect gases that are denser than air. (gases that have a higher relative atomic mass than nitrogen)
• Upward delivery is used to collect gases that are less dense than air. (gases with lower relative atomic masses than nitrogen).
• Concentrated sulfuric acid is used as a method for drying gases. Can be used for most gases. (eg chlorine and hydrogen chloride) It is not suitable for gases that react with sulfuric acid. (eg ammonia)

  
• Quicklime (calcium oxide) is used as a method for drying gases. (eg ammonia) It absorbs moisture and carbon dioxide from the air, so it must be freshly heated before use. Cannot be used to dry gases which react with calcium oxide. (eg carbon dioxide)

  
• Fused calcium chloride is used as a method for drying gases. (eg hydrogen, nitrogen, carbon dioxide) It readily absorbs moisture from the air, so it must be freshly heated before use. This method cannot be used to dry gases which react with calcium chloride. (eg ammonia)

  
• Separating solid-solid mixtures:

  1. Magnetic attraction (Magnet used to separate magnetic solids from non-magnetic solids)
  2. Sieving (sieve used to separate solids with different particle sizes)
  3. Using suitable solvents (In which only one of the solids is soluble in the solvent)
  4. Sublimation (Used to separate a substance that changes from solid to gaseous state directly.
• Separating solid-liquids mixtures:

  1. Filtration (separate insoluble solids from liquids. Solid that remains on filter paper is the residue. Liquid that passes through the filter paper is the filtrate.)
  2. Evaporation to dryness (separate a dissolved solid from its solvent by heating the mixture until all the solvent has vaporised)
  3. Crystallisation (used for solutes that decomposes when heated. To obtain a pure solid from its saturated solution. A saturated solution is when no more solute can be dissolved in it.)
• Separating solid-liquids mixtures:

  Simple distillation (separate a pure solvent from a solution)

  
• Separating liquid-liquids mixtures:

  1. Separating funnel (separate immiscible liquids)

  
• Separating liquid-liquids mixtures:

  Chromatography (separate a mixture of substances which have different solubilities in a given solvent. Rf value= distance travelled by substance/distance travelled by solvent. Locating agents are used to identify colourless substances on a chromatogram)

  
• Separating liquid-liquids mixtures:

  Fractional distillation (separate miscible liquids with different boiling points)

  
• A pure substance has a specific melting and/or boiling point under fixed conditions
• Heterogenous mixture - nonuniform composition, e.g. sand and water, soil, blood.
• Homogeneous mixture - uniform composition throughout, e.g. sugar solutions, air, petrol.
• KPE liquids:

  1. Particles arrangement: closely packed in a disorderly manner (CPd)
  2. Attractive forces between particles: less strong
  3. Kinetic energy: low
  4. Particle movement: slide past one another freely throughout the liquid
  5. Shape: indefinite
  6. Volume: definite
  7. Not compressible

  
• KPE solids:

  1. Particle arrangement: very closely packed in an orderly manner (CPo)
  2. Attractive forces between particles: very strong
  3. Kinetic Energy of particles: very low
  4. Particle movement: vibrate about fixed positions
  5. Shape: definite
  6. Volume: definite
  7. Not compressible

  
• KPE gases:

  1. Particle arrangement: Far apart in a disorderly manner (FAd)
  2. Attractive forces between particles: very weak
  3. Kinetic energy of particles: high
  4. Particle movement: move quickly and randomly in any direction
  5. Shape: indefinite
  6. Volume: indefinite
  7. Compressible

  
• Movement of particles in liquids:

  Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.

  Factors affecting:

  1. Effect of temperature (higher temperatures leads to faster diffusion)
  2. Effect of particle mass ( Greater particle mass/relative atomic mass leads to slower diffusion. eg hydrogen chloride gas and ammonia gas in a tube)
• Volatile substances turns into gases easily
• Proton:

  1. relative mass: 1
  2. Relative charge: +1
  3. Location in atom: nucleus
• Neutron:

  1. relative mass: 1
  2. Relative charge: 0
  3. Location in atom: nucleus
• Electron:

  1. relative mass: 1/1840
  2. Relative charge: -1
  3. Location in atom: electron shell
• Nuclide notation

  A) nucleon (mass) number

  B) proton (atomic) number

  C) charge

  
• Ion is a charged particle formed when an atom loses or gain electrons.
• Isotopes are atoms of the same element with the same number of protons but different number of neutrons. (different mass)