Unit -1 States of matter

• States of matter


  • Solid
  • Liquid
  • Gas
• Solid


  • Definite shape
  • Definite volume
  • Particles in fixed arrangement
  • Strong force of attraction between particles
  • Most particles per cm³
• Liquid


  • No definite shape
  • Definite volume
  • Particles in random arrangement
  • Weak force of attraction between particles
  • Moderate number of particles per cm³
• Gas


  • No definite shape
  • No definite volume
  • Particles in random arrangement
  • Negligible force of attraction between particles
  • Least particles per cm³
• States of matter are interchangeable when temperature or pressure changes
• Solid to liquid


  Melting
• Liquid to gas


  1. Evaporation

  2. Boiling
• Gas to solid


  Sublimation
• Melting and boiling points are the temperatures at which a solid turns into a liquid and a liquid turns into a gas respectively
• Neon has a melting point of -20°C, boiling point of -196°C, and exists as a gas at room temperature
• Dry ice (solid CO2) and mothballs (solid iodine) undergo sublimation, where the solid turns directly into a gas
• Volatile


  Evaporates easily
• Boiling point


  Indicates volatility, higher boiling point means less volatile
• Pure substance


  Contains only one substance, no unwanted substances (impurities)
• Pure substances have sharp, distinct, and fixed melting and boiling points
• Impurities


  Decrease melting point, increase boiling point
• Checking purity


  1. Measure melting and boiling points

  2. Use chromatography
• Substances that must be pure


  • Food and drinks
  • Drugs (medicine)
• Temperature remains constant during melting because the energy supplied is used to overcome the force of attraction between particles in the solid
• Kinetic particle theory


  • Solids - particles vibrate
  • Liquids - particles move randomly
  • Gases - particles move randomly at high speeds
• As temperature increases


  Particle movement becomes faster
• Diffusion


  Movement of particles from high to low concentration
• Rate of diffusion


  Depends on molecular mass and temperature
• Diffusion rates


  • NH3 faster than HCl
  • H2 faster than CO2
• Demonstrating diffusion


  Place cotton wool soaked in NH3 solution and cotton wool soaked in HCl solution in a beaker, a white ring of NH4Cl forms
• Solution


  Solute dissolved in solvent
• Types of solutions


  • Soluble solute
  • Insoluble solute (precipitate or suspension)
• Solubility and temperature


  More solute can dissolve at higher temperatures
• Saturated solution


  No more solute can dissolve at a given temperature
• Paper chromatography


  1. Separate soluble coloured substances using paper and solvent

  2. Measure distance travelled to determine solubility and purity
• Retardation factor (Rf)


  Ratio of distance travelled by solute to distance travelled by solvent, used to identify substances
• Uses of chromatography


  • Separation
  • Purity
  • Identification
• Mixture


  When mixed without chemical combination, form
• Pure substances


  Can be separated using Methods of Separation and Purification
• Methods of Separation and Purification


  • Filtration
  • Evaporation to dryness
  • Crystallisation
  • Paper chromatography
• Separating an insoluble solid from a liquid

  Filtration
• Separating a soluble solid from a liquid

  1. Evaporation to dryness

  2. Crystallisation
• Separating a solid that decomposes on strong heating


  Sublimation
• Separating immiscible liquids


  Using a separating funnel
• Separating miscible liquids


  Fractional distillation