3B Sublimation by https://padlet.com/neo_si_lie_charles/ldq8irok08iq Made with no regrets, whatsoever en-us 2018-01-23 10:06:18 UTC 2018-01-31 13:14:19 UTC hello@padlet.com No. 1 What types of mixtures can be separated by sublimation? https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/224588638
  • Sublimation can be used to separate a mixture of solids in which one solid sublimes and the others do not.
  • Sublimation is the phase transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. 
  • You heat the mixture and then cool the vapours separately to recover the sublimed solid. 
  • Some substances that sublime are iodine, ammonium chloride, naphthalene, camphor, and sulfur.
    • ]]>     2018-01-25 11:20:44 UTC https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/224588638     No. 2 Using an example of a suitable mixture, describe how can we separate the mixture by sublimation. https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/224589338
  • You can separate ammonium chloride from sodium chloride by heating the mixture as shown below.
    cbse.meritnation.com
  • The ammonium chloride vapour deposits as solid crystals on the cool walls of the funnel. The salt stays in the china dish.


    • ]]>     2018-01-25 11:23:38 UTC https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/224589338     No. 5 What are the applications of sublimation? https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/225300696 Examples,
    • Air fresheners solid slowly sublimes and dissolves in air. It than releases a pleasant smell in the toilet for a period of time. 
    • Because of weak forces, moth balls are made out of naphthalene (a volatile white crystalline compound produced by the distillation of coal tar) which sublimes and are used to drive away moths and some insects.
    • Dry ice or solid carbon dioxide is used for cooling items and neutralizing alkalies. It breaks down and directly turn into carbon dioxide gas rather than a liquid.
    ]]>     2018-01-27 15:43:39 UTC https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/225300696     No.4 What are the precautions, if any, to take note of sublimation? https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/225327835
  •  Dry ice can be hold very briefly, however when squeeze,  one could suffer frostbite which can lead to burns and scars as the temperature of the dry ice is minus 79 degrees Celsius.
    •            -Safety precaution: Always wear gloves when handling dry ice or use tongs or spoon.
               -Note: When performing demonstrations, wear gloves even when you are using tongs.
    •  Expansion of carbon dioxide gas produced can generate high pressures in sealed airtight containers
              -Safety precaution: Store dry ice in non-airtight containers. Never store in airtight containers with screw caps. The sublimation of dry Ice to Carbon Dioxide gas will cause any airtight container to expand or possibly explode.
               -Note: Storing dry ice in a standard cooler box with the lid on is safer as the carbon dioxide can leak out through small gaps between the lid and cooler box
      
    ]]>     2018-01-27 21:54:28 UTC https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/225327835     No. 3 What are the principles (key scientific concepts) involved in sublimation. https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/225361531
  • Sublimation is an endothermic process that occurs at temperatures and pressures below a substance's triple point in its phase diagram. 
  • The reverse process of sublimation is deposition, in which a substance passes directly from a gas to a solid phase. 
  • At normal pressures, most chemical compounds and elements possess three different states at different temperatures. In these cases, the transition from the solid to the gaseous state requires an intermediate liquid state.
  •  All solids that possess an appreciable vapour pressure at a certain temperature usually can sublime in air (e.g. water ice just below 0 °C). 
  • For some substances, such as carbon and arsenic, sublimation is much easier than evaporation, because the pressure of their triple point is very high, and it is difficult to obtain them as liquids.
  • The term sublimation refers to a physical change of state and is not used to describe the transformation of a solid to a gas in a chemical reaction.
  •  For example, the dissociation on heating of solid ammonium chloride into hydrogen chloride and ammonia is not sublimation but a chemical reaction. 
  • Similarly the combustion of candles, containing paraffin wax, to carbon dioxide and water vapor is not sublimation but a chemical reaction with oxygen. 
  • Sublimation requires additional energy and is an endothermic change. The enthalpy of sublimation (also called heat of sublimation) can be calculated by adding the enthalpy of fusion and the enthalpy of vaporization.

    • ]]>     2018-01-28 10:32:08 UTC https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/225361531     Video on sublimation. https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/226072633 https://vimeo.com/2899706]]> 2018-01-30 13:59:57 UTC https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/226072633 Picture of sublimation https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/226082838
    ]]>     2018-01-30 14:17:38 UTC https://padlet.com/neo_si_lie_charles/ldq8irok08iq/wish/226082838