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)