Genchem 1

• When matter changes state, its mass remains the same
• When sugar burns, a chemical change is evident
• Sucrose has a chemical formula of C12H22O11
• Evaporation is used to obtain dissolved solid from the solution
• A magnet could be used to separate sand and iron filings
• Two or more substances mingled together, but not chemically combined are collectively known as a mixture
• Seawater is a mixture
• Chemistry


  The study of the composition, structure, properties and behavior of matter
• Matter has two characteristics: it has mass and it occupies space
• Forms of matter


  • Stars
  • Air
  • Gasoline
  • Chair
  • Meat
  • Tissues in brain
• Rigid substances

  • Have definite shapes that are difficult to change
• Non-rigid substances


  • Take the shape of any container into which they are poured
• States of matter

  • Solid
  • Liquid
  • Gas
• The state of matter depends on the strength of the forces among the particles contained in the matter
• Physical properties


  Characteristics that can be observed or measured without changing the composition of the substance
• Chemical properties


  Ability of a substance to form new substances
• Water molecules are still intact in physical changes like melting and boiling
• In electrolysis, water decomposes into hydrogen and oxygen, which is a chemical change
• Elements

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


  • Iron
  • Aluminum
  • Oxygen
  • Hydrogen
• Compounds

  Substances made up of atoms of different elements combined in a specific way
• Compounds can be broken down into their constituent elements through chemical changes
• A compound always contains atoms of different elements
• The properties of a compound are typically very different from those of the elements it contains
• Mixture


  Something that has variable composition
• Pure substance


  Something that always has the same composition, either an element or a compound
• Mixtures can be separated into pure substances: elements and/or compounds
• Homogeneous mixture

  A mixture that is the same throughout
• Heterogeneous mixture


  A mixture that contains regions with different properties
• Homogeneous mixture

  A mixture where all regions have the same properties, also called a solution
• Homogeneous mixtures

  • Air
  • Brass
• Heterogeneous mixtures

  • Sand in water
• In a homogeneous mixture (solution), different amounts of components can be mixed but the composition does not vary from region to region
• Mixtures are physical combinations of substances that do not change into other substances
• Separation techniques


  • Depend on the type of mixture and the physical properties of the components
  • Depend on whether you want to retrieve all components or not
• Physical properties that can be used for separation


  • Melting point
  • Boiling point
  • Size
  • Solubility
  • Density
  • Magnetism
  • Other forms of attraction
• Separation techniques for heterogeneous mixtures


  • Decanting
  • Sieving
  • Filtration
  • Separating funnel
  • Centrifugation
  • Magnetic separation
• Separation techniques for homogeneous mixtures

  • Distillation
  • Chromatography
• Decanting


  Separating a dense, insoluble substance from a heterogeneous mixture by pouring off the liquid layer
• Sieving


  Separating a mixture based on different sizes of components