MATTER IS ALL AROUND YOU

• Matter is anything that occupies space and has mass
• Chemistry is the study of matter, its different properties, and the different changes it can undergo
• Steven Weinberg: 'The progress of science has been largely a matter of discovering what questions should be asked'
• Changes in state of water

  1. Solid (ice)

  2. Liquid

  3. Gas (vapor)
• Physical properties


  Characteristics of a substance that can be observed without changing its composition
• Chemical properties


  Ability of a substance to form new substances
• Physical changes do not affect the composition of a substance
• Chemical changes cause a substance to be decomposed into new substances
• Extensive property


  Property that depends on the amount of matter in a sample
• Intensive property


  Property that depends only on the type of matter in a sample and not on the amount
• Element


  Fundamental substance that cannot be broken down into other substances by chemical means
• Compound


  Substance made up of atoms of different elements combined in a specific way
• Elements contain only one kind of atom, compounds contain atoms of different elements
• Mixture


  Something with variable composition
• Pure substance


  Substance with a fixed composition, either an element or a compound
• Crystallization


  Separates mixtures based on differences in solubility
• Homogeneous mixture


  A solution that does not vary in composition from one region to another
• Air


  • A homogeneous mixture of gases
• Brass


  • A homogeneous mixture of the metals copper and zinc
• Heterogeneous mixture


  Contains regions that have different properties from those of other regions
• Sand in water


  • A heterogeneous mixture with one region containing water and another region containing mostly sand
• Crystallization


  1. Separates mixtures based on differences in solubility

  2. Dissolve at elevated temperature and allow to cool slowly

  3. Allow liquid solvent to evaporate

  4. Least soluble substance forms crystals first and can be removed by filtration
• Recrystallization


  1. Dissolve impure substance in minimum amount of hot solvent

  2. Gravity filter hot solution

  3. Allow solution to cool to room temperature, then cool further in ice bath

  4. Collect resulting crystals by vacuum filtration

  5. Dry and weigh crystals
• Evaporation


  1. Separates components of a mixture with a dissolved solid in a liquid

  2. Liquid is evaporated, leaving behind the solid
• Distillation


  1. Separates components of a liquid mixture by heating and cooling to exploit differences in volatility

  2. Liquid mixture is heated to boil

  3. Component with lower boiling point vaporizes and condenses in condenser

  4. Distilled liquid is collected
• Filtration


  1. Separates undissolved solid from a liquid mixture

  2. Mixture is poured through a filter paper in a funnel

  3. Solid remains in the funnel, liquid (filtrate) passes through
• Chromatography


  • Separates mixtures into components based on differences in affinity for stationary and mobile phases
  • Stationary phase (e.g. alumina, silica, paper)
  • Mobile phase (solvent or solvent mixture, called eluent)
  • Mixture is placed on stationary phase, mobile phase carries components with different affinities at different rates
• Chromatography is the most important method for separating mixtures into components
• Gases have neither a definite shape nor volume, with particles that are far apart and move freely in all directions.
• Solids have fixed shapes and volumes, while liquids take the shape of their container but keep the same volume.
• Volume is how much space an object occupies, measured in cubic metres (m3) or litres (L).
• Mass is the amount of matter something contains, measured in kilograms (kg).
• The solid state of matter has a definite shape and volume, with particles arranged in a fixed, orderly pattern.