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Lss kpt Lss kpt Presentation Transcript

  • Kinetic Particle Theory
  • Learning Outcomes • At the end of the lesson, the students should be able to: – describe the solid, liquid and gaseous states of matter and explain their interconversion in terms of the kinetic particle theory and of the energy changes involved
  • States of Matter • Matter can exist as a solid, a liquid or a gas. • Kinetic particle theory states that – all matter is made up of tiny particles and – that these particles are in constant random motion.
  • Comparing the 3 states Property Solid Liquid Gas Shape Fixed Not fixed Not fixed Volume Fixed Fixed Not fixed Compress- ibility Cannot be compressed Cannot be compressed Can be compressed Forces of attraction between particles Strong Weaker than that in solid weak
  • Comparing the 3 states Property Solid Liquid Gas Arrangement of particles closely packed in orderly manner closely packed in random order far apart
  • Comparing the 3 states Property Solid Liquid Gas Movement of particles cannot move, vibrates and rotates about their fixed position free to move within the liquid, vibrates and slides over one another free to move, move rapidly in any direction
  • Changes in States of Matter • The physical state of a substance depends on the temperature and pressure of the surroundings. • For example – At room temperature (25 o C), water is in the liquid state. – At -10 o C, water is in the solid state.
  • Changes in State • Heat is a form of energy. • When matter is heated, the particles absorb energy. • When matter is cooled, the particles lose energy. • the heat taken in or given out causes the kinetic energy of the particles to change. • Hence, the substance changes it state.
  • Changes in States of Matter boilmelt freeze condense sublime condense
  • Changes in States of Matter Melting Boiling Freezing Conden- sation Sublima- tion Physical change Solid to liquid liquid to gas liquid to solid gas to liquid solid to gas Energy change Energy absorbed Energy absorbed Energy given out Energy given out Energy absorbed
  • Changes in States of Matter • What happens during melting – particles gain energy, – particles vibrate faster, – particles overcome attractive forces between them, – particles break away from their fixed positions
  • Changes in States of Matter • What happens during boiling – particles gain kinetic energy, – particles move faster, – particles overcome forces holding them together, – particles spread far apart, – particles move rapidly in all directions
  • Changes in States of Matter • What happens during freezing – particles lose kinetic energy, – particles move more slowly until they no longer have enough energy to move about freely, – particles settle into fixed position
  • Changes in States of Matter • What happens during condensation – particles lose energy, – particles move more slowly, – becomes a liquid
  • Sublimation • Particles at the surface of the solid have enough energy to break away from the solid and escape as a gas
  • Changes in States of Matter Melting Boiling Freezing Conden- sation Temp at which change occurs melting point boiling point Freezing point -
  • Wake Up Call 1 1. When water vapour condenses to water, the particles in the vapour A gains energy. B decrease in density C move closer to each other D mover further apart from each other. Answer: C
  • Wake Up Call 1 1. Three substances have the following properties: X: melts at -180 o C and boils at -167 o C Y: has shiny crystalline surface at r.t.p Z: can flow and take the shape of container at rtp; has boiling point of 160 o C What is the state of each substance at room temperature and pressure? X Y Z A Gas Solid Liquid B Gas Liquid Liquid C Liquid Solid Solid D Gas Liquid Solid Answer: A
  • Wake Up Call 1 3 (a) For the following substances state the physical state (solid, liquid or gaseous) they are in at a temperature of 1500 o C. Substance Melting Point / o C Boiling Point / o C Physical State Copper 1084 2562 Calcium 842 1484 Iron 1538 3134 Gold 1064 2856
  • Wake Up Call 1 b) Hence draw and describe the arrangement and movement of particles of copper, calcium and iron at the temperature of 1000 o C. (i) Copper Arrangement: – closely packed in orderly manner Movement: – cannot move, vibrates and rotates about their fixed position (ii) Calcium Arrangement – closely packed in random order Movement – free to move within the liquid, vibrates and slides over one another
  • Temperature Changes • When matter is heated energy causes temperature to increase. • Temperature stops increasing at melting / boiling points. • Particles absorb the heat energy to vibrate faster and move further apart. • Matter changes state. Figure showing the heating curve of water