1.5: chemical and physical properties and changes

properties and changes

• change: the act of making something different or undergoing a process that makes something different
• physical change: a change during which the identity of the underlying substance does not change
  • eg. melting, dissolving, boiling
• chemical change: a change during which something new is formed
• evidence of chemical change
  • evolution of a gas
  • change in color
  • formation of a precipitate
  • release or absorption of energy
  • eg. release of heat, light, sound, change of temperature
• property: a quality, attribute, or characteristic of something
• physical property: a property of matter that can be observed without changing the substance
  • eg. color, density, conductivity, physical state, solubility
• chemical property: a property of matter desccrived as a substance’s ability to participate in chemical reactions; to observe a chemical property, the substance must be changed
  • eg. reactivity with oxygen, flammability, reactivity with acids
• intensive property: a property independent of the amount of material in the sample
  • eg. density, boiling point, color, fammability, conductivity
• extensive property: a property dependent on the amount of material in the sample
  • eg. mass, volume, energy

separating mixtures

• mixtures can be separated based on the physical properties of the components in the mixtures
• separation methods include:
  • filtration (separation by size)
  • distillation (separation by boiling point)
  • can separate a homogeneous mixture into its components
  • chromatography (separation by solubility)