Pure substances and mixtures

Pure substances and mixtures

1. heterogenous and homogenous mixtures

   • heterogeneous
     • a substance is heterogenous if its different components are distinguished
       • examples
         • Granite
   • homogeneous
     • a substance is homogeneous if its components cannot be distinguished with the naked eye.
       • examples
         • Quartz

2. Pure substances and mixtures

   • Pure substance
     • materials formed from a single substance are called pure substances
       • pure substances are caracterized by having specific physical properties such as melting and boiling temperatures
         • examples
           • water
           • salt
   • Mixtures
     • Materials resulting from the physical combination of two or more substances are called mixtures
       • the pure substances that make up a mixture are callled components
         • There are two types of mixtures
           • heterogeneous mixtures
             • The components in an heterogeneous mixture can be seen with the naked eye and are distributed unevenly
               • There different methods for separating heterogeneous mixtures
                 • sieving
                 • filtration
                 • sedimenation and decantation
                 • decantation
                 • flotation
                 • centrifuging and decantation
                 • leaching
                 • magnetic separation
           • homogeneous mixtures or solutions
             • The components in an homogeneous mixture can neither be distinguished with the naked eye nor observed under the light of a microscope, and their components are evenly distributed
               • Two types of components can be distinguished in a mixture
                 • solvent
                   • is the main component of a solution
                 • solutes
                   • are the componets of the mixture of wich there are lesser amounts
                 • depending on the state of matter of the solvent, a solution may be
                   • solid solution
                   • liquid solution
                   • gaseous solution
             • Almost homogeneous mixtures
               • there is a group of heterogeneous mixtures that can only be distinguished under the microscope, these type of mixtures can appear homogeneous under the naked eye
                 • example
                   • colloids
                     • are mixtures in which a minor component (dispersed phase) is dispersed within another major component (dispersion medioum)
                       • Different types of colloids
                         • Aerosols
                           • aerosols are colloids with a gaseous dispersion medioum and a dispersed phase formed of solid or liquid particles
                             • example
                               • clouds
                         • Gels
                           • tiny particles of liquid are inmersed in a solid dispersion medioum
                             • example
                               • jelly
                         • Foams
                           • foams are colloids in which a liquid dispersion medioum contains gaseous particles that give rise to small bubbles
                             • example
                               • sea water
                         • Sols
                           • sols are colloids formed by very tiny solid particles dispersed in a liquid medioum
                             • example
                               • paint
                         • Emulsions
                           • emulsions are produced when two immiscible liquids mix by mean of the dispersion by minute droplets or micelles of one in the other
                             • example
                               • milk
             • Physical methods of separation
               • chromatography
               • vaporization
               • distillation

3. Chemistry quiz