Chemistry Note

• Particles Theory


  The partides in solids are arranged in regular rows, with the particles touching each other. They are held firmly in place by very strong force of attraction. They can only vibrate - they cannot move or change places.
• Particles in liquids


  The particles are arranged with the particles touching each other but not in a pattern of rows. They are held together by strong force of attractions but weaker than in solid. They can move past each other.
• Particles in a gas


  The particles do not touch each other. They are not attracted to each other, they have weak or absent force of attraction between them. They can move freely and randomly in all direction.
• Explain why solids and liquids cannot be compressed


  Both solid and liquid take up the shape of container filling the whole space without much gaps. They also have fixed volume so they cannot be compressed.
• Explain why a solid expands when it is heated


  When the solid is heated, heat energy is transferred to the particles and they vibrate more. This situation takes up more space so the solid expands.
• Properties


  • Solid
  • Liquid
  • Gas
• Particles Properties


  • Shape
  • Volume
  • Separation between particles
  • Arrangement
  • Attractive forces between particles
  • Movement of Particles
• Change in state


  1. Melting (solid to liquid)

  2. Boiling (liquid to gas)

  3. Condensation (gas to liquid)

  4. Freezing (liquid to solid)

  5. Sublimation (solid to gas)

  6. Deposition (gas to solid)
• Endothermic reaction


  Heating & heat energy absorbed
• Exothermic reaction


  Cooling & heat energy released
• Changing State


  1. Melting (solid to liquid)

  2. Boiling/evaporation (liquid to gas)

  3. Condensation (gas to liquid)

  4. Freezing (liquid to solid)

  5. Sublimation (solid to gas)

  6. Deposition (gas to solid)
• Melting


  Solid particles gain heat energy. They vibrate faster. The forces of attraction between them become weaker. Some forces of attraction are broken down. Finally, solid changes into liquid.
• Condensation (gas to liquid)


  Gas particles get heat energy. They move faster. The forces of attraction between them became stronger. New forces of attraction are formed. Finally, gas changes into liquid.
• Summary, changing states in terms of kinetic particles theory


  • heat energy (for)
  • movement (faster or slower)
  • attractive forces (weaker or stronger)
  • arrangement (closely packed, just touched, far apart)
• Diffusion


  Random movement of different particles from a region of higher concentration to a region of lower concentration to fill the whole space available. It can take place in liquid and gas.
• Factors affecting speed of diffusion


  • Temperature (higher temperature = faster diffusion)

  Mass of particles (lighter particles diffuse faster)

  Concentration of reactants (have respective ratio of concentration to diffuse rapidly)
• Diffusion of solid in liquid

  Small particles break away from the crystal when dissolved in water. Particles move out randomly in all directions.
• Diffusion of liquid in air

  The reddish brown bromine liquid particles evaporate into the gas particles. The gas particles move out randomly in all directions.
• Diffusion of air


  Hydrogen chloride gas diffuses. Ammonia gas diffuses. Where the white ring of ammonium chloride forms.
• Brownian Motion


  Random, irregular bombardment of visible particles by particles of air or water in all direction.
• Similarities and differences between brownian motion and diffusion


  Similarity: Random movement of particles

  Difference: Brownian motion with help of air or water molecules, visible particles in all direction. Diffusion of small particles from higher to lower concentration.
• Boiling


  Rapid process, occurs at a fixed temperature, takes place inside the whole liquid, bubbles are formed.
• Evaporation


  Slow process, occurs at any temperature, takes place on the surface of the liquid, bubbles are not formed.
• Sublimation


  The process by which a solid has directly changed into a gas without passing through a liquid state.
• Deposition


  The process by which a gas directly makes a solid without going through a liquid state.
• Sublimation


  Gas makes directly a solid without going through liquid state
• Mixture


  • Homogenous mixture
  • Heterogenous mixture