states of matter

• Materials can exist in three states:

  • SOLID
  • LIQUID
  • GAS

  These states can be represented using a SIMPLE MODEL.

  
• The SIMPLE MODEL:

  Uses SMALL, INELASTIC SPHERES as particles.

  • However, in reality, The particles are atoms, ions or molecules
  • Also does not show the ACTUAL FORCES between particles
  • so there's no way of knowing how strong they are or how many there are.

  
• CHANGING STATE:


  The process where substances CHANGE between solid, liquid, & gas phases.

  • This involves energy changes & particle movement.

  
• The amount of ENERGY needed to change state from solid to liquid & from liquid to gas.

  • depends on the STRENGTH of the forces between the particles of the substance.

  
• Individual atoms themselves do not share the same properties as bulk matter.

  
• HEATING A SOLID:

  • When a solid is heated to its MELTING POINT
  • its particles gain energy & VIBRATE more
  • weakening the forces holding them together.
  • This is known as MELTING.

  
• HEATING A LIQUID:

  Heating a liquid to its BOILING POINT gives particles more energy to move faster

  • leading to BOILING or EVAPORATING where the liquid becomes a gas.

  
• FREEZING:


  When the particles in a liquid are cooled to their MELTING POINT

  • They lose energy & move less
  • they form more bonds & the liquid becomes a solid.

  
• CONDENSING:


  A gas turns into a liquid when it is cooled to its BOILING POINT

  • as particles lose energy & form bonds.

  
• Particle theory:


  explains how matter changes state depending on the energy & forces present between the particles in the substance.
• The amount of energy needed to change from a solid to a liquid & from a liquid to a gas depends on the STRENGTH of the forces between the particles.
• There's types of substance, that contain different amounts of elements & compounds:

  • Since each substance contains different particles
  • the amount of energy needed to change the state of them is

  DIFFERENT for each individual substance.
• The STRONGER the FORCES between the particles, the higher the energy needed for melting & boiling to occur.

  • When substances are heated, the particles ABSORB heat energy which causes its particles to VIBRATE more.
• When the substance reaches the MELTING POINT:

  • The bonds between the particles break & the solid MELTS into a liquid.
  • When it is heated further and the boiling point is reached
  • The particles gain enough energy for the forces between them to break and they turn into a GAS.
• Disadvantages of the particle theory:

  • It assumes all particles to be SOLID, SPHERICAL & INELASTIC, when they aren’t.
  • It doesn’t consider the differences caused by different particles, like atoms, ions & molecules.
  • It doesn't consider the INTERMOLECULAR forces between particles in different substances.
• To predict the state of a substance:

  • BELOW the MELTING POINT, a substance is SOLID.
  • ABOVE the BOILING POINT, it's a GAS.
  • BETWEEN these two points, it's a LIQUID.

  
• • Hydrogen is not shown as molecules
  • particles are shown as solid & spheres
  • does not show the weak forces between particles
  • does not show the movement / speed of particles
  • is only 2D