Phase Changes
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Phase Changes

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A set of slides created to teach Phase Changes to learners at Bishops Diocesan College in Cape Town.

A set of slides created to teach Phase Changes to learners at Bishops Diocesan College in Cape Town.

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Phase Changes Phase Changes Presentation Transcript

  • LIQUID Solid Phases of Matter PLASMA GAS The FOUR states of matter are determined by the amount of …………………. available. + + + + + +
  • LIQUID Solid Phases of Matter INCREASING ENERGY PLASMA GAS The FOUR states of matter are determined by the amount of ENERGY available. + + + + + +
  • Phases of Matter ENERGY/ Movement FORCES POSITION/ ArrangementShape PLASMA GAS LIQUID SOLID View slide
  • Phases of Matter High – particles breaking up High – Rapid random motion Higher Slide over each other Low energy vibrate ENERGY/ Movement None Very weak Weakened Very Strong FORCES Changing Random Fill any container Random Take shape of container Fixed POSITION/ ArrangementShape PLASMA GAS LIQUID SOLID View slide
  • LIQUID Solid Phase changes GAS
    • Think about what is involved when a substance has to change from one phase to another . Name each process and describe what needs to happen in terms of:
    • position of and spaces between particles
    • forces between particles
    • energy of particles.
  • Phase Changes Process ENERGY FORCES PARTICLE (positions) Solid  GAS Liquid  Gas Solid  Liquid
  • Melting (Fusion)
    • When a solid melts the particles need to undergo a number of changes:
    • Solid --> Liquid:
      • the spaces between the particles increase
      • The energy of the particles increases
      • The forces between the particles are weakened
    • Each of these changes requires energy to be put in.
    • The temperature stays constant because the extra energy is being used to weaken the forces .
    Melting
  • Boiling/(Evaporation)
    • When a liquid boils the particles need to undergo a number of changes:
    • Liquid --> Gas:
      • the spaces between the particles increase
      • The energy of the particles increases
      • The forces between the particles are weakened
    • Each of these changes requires energy to be put in .
    • The temperature stays constant because the extra energy is being used to weaken the forces .
    Boiling/ (Evaporation ) Liquid Gas
  • Condensation
    • When a gas condenses:
      • the spaces between the particles decrease.
      • The energy of the particles decreases (move slower).
      • The forces between the particles are strengthened .
    • Each of these changes requires energy to be taken out . (Given off).
    Condensing Energy given off Energy given off Liquid Gas The temperature stays constant because strengthening forces releases energy which replaces that which has been removed.
  • Freezing
    • When a liquid freezes (fuses) the particles need to undergo a number of changes:
    • Liquid --> solid:
      • the spaces between the particles decrease.
      • The energy of the particles decreases (move slower).
      • The forces between the particles are strengthened .
    • Each of these changes requires energy to be taken out . (Given off).
    Fusion Energy taken out Energy taken out The temperature stays constant because strengthening forces releases energy which replaces that which has been removed.
  • Phase Change - Snow
    • Explain why the air is warmer when it snows than when the snow is thawing (melting).
  • Boiling vs Evaporation Wind Water molecules (high energy) escape from the surface of the liquid. The remaining particles have less energy - lower temperature ENERGY IS REMOVED FROM THE WATER (Cooling Effect). All liquids have their own vapour (gas). This vapour has a pressure which increases with temperature . When the vapour pressure equals the pressure outside the liquid the liquid boils. GAS LIQUID IN BOILING ENERGY MUST BE PUT IN. The temperature of the water does not change as the energy is used to change the phase.
  • Phase Changes Process ENERGY FORCES PARTICLE (positions) Solid  GAS Liquid  Gas Solid  Liquid
  • Boiling vs Evaporation
    • Low Temp
    • Energy taken out.
    • Not affected by pressure.
    • High Temp
    • Energy put in
    • Affected by atmospheric pressure
    Differences
    • Change water to water vapour
    • Particles undergo same changes (increase spaces, energy, weaker forces)
    Similarities Evaporation Boiling
  • Heating Curve During a phase change the energy is used to overcome forces between the particles and increase the spaces between them - the temperature stays the same so the graph is flat.
  • Phases Task
    • Find out the melting point and boiling points of the following substances.
      • Hydrogen oxide (H 2 O) Mp: 0 o C, Bp: 100 o C
      • Nitrogen - gas 80% of the air
        • (N 2 ) Mp: -210 o C, Bp: -195 o C
      • Mercury - liquid Mp: -39 o C, Bp: 357 o C
    • What factors can affect the boiling point of water?
      • Altitude (pressure) - higher (alt) --> lower (bp)
      • Dissolved substances --> raise the boiling point.