States of matter

• Matter is made up of tiny particles and can exist in three main states:

  • solid
  • liquid
  • gas

  
• The density of a substance is a measure of how tightly packed its particles are.
• In solids, particles are packed closely, which makes solids the MOST DENSE state of matter.
• • Liquids are less dense than solids because their particles are more spread out.
• • Gases are the LEAST DENSE, as their particles are far apart and move freely.
• Changes of state are PHYSICAL changes.

  • which differ from chemical changes as the material recovers its original properties, if the change is reversed.

  A) melting

  B) evaporation / boiling

  C) deposition

  D) sublimation

  E) condensation

  F) freezing

  
• Evaporation:


  Happens when a liquid's temperature is same as its surroundings.

  • The particles having highest kinetic energy will move faster and escape.
  • The average kinetic energy of the remaining particles in liquid decreases, so the temperature decreases.
• Sublimation:


  When a substance changes from a solid to a gas without going through the liquid phase.

  • A physical change.
  • E.g. dry ice
• On heating solids:

  • Particles gain kinetic energy
  • Transferred to the particle's kinetic energy stores
  • The particles start to vibrate faster
  • The bonds between solid particles become weak
  • At a certain temperature (melting point), the particles have enough energy to break free of their bonds
  • They change state to liquid.
• On heating liquids:

  • Particles gain kinetic energy
  • They start to move faster
  • When The bonds between liquid particles break
  • They change state to gas.
• As the particles vibrate more:

  • some of the forces of attraction between them weaken (or are overcome)

  or

  • some of the bonds between them break

  causing the solid to melt into a liquid.
• The particle / kinetic model consider each particles are:


  • Small
  • Solid 
  • Inelastic
  • Spheres
• SOLIDS:



  There's strong forces of attraction between particles:

  • which tightly packs them in a FIXED position to form a REGULAR lattice structure.
  • It gives a DEFINITE SHAPE & VOLUME, so it can’t flow like a liquid.
  • So they can only vibrate in a fixed position, & are not free to move.
  • Incompressible
  • High density
  • They have the lowest internal energy.

  Each particle has the same size.

  
• LIQUIDS:



  There’s weak forces between the particles:

  • Allows Particles to move around each other & spaces between them change.
  • Allows liquids to flow & take the shape of their container, so the overall shape can change.
  • They stick together fairly compactly, meaning they have a definite volume.
  • Particles are close together & arranged randomly.
  • Half of the particles are touching each other.
  • Medium density
  • Slightly compressible

  Each particle is the same size.

  They have more internal energy than solids.

  
• GASES:


  VERY WEAK OR NO FORCES of attraction between particles:

  • So Particles are far apart & arranged randomly with all being the same size
  • So Particles move freely at different speeds in all directions
  • meaning they move in a straight line till they deflect by solid wall & other gas particles randomly.
  • So it has NO FIXED SHAPE or volume & will always fill a container.
  • as they spread out as far as possible, with lots of empty space between them.
  • This gives a low density

  Highly compressible

  They have the highest internal energy.

  
• When a gas is heated, the particles gain kinetic energy and move faster:


  • If it's in an expandable container (like a balloon) the volume will increase.
  • If it's in a fixed container, the volume of the gas is fixed, so the pressure will increase.

  
• Condensation:


  In gases, the particles have enough energy to overcome the attractive forces between them & spread out randomly. 

  • If the temperature is lowered, they will no longer be able to overcome these attractive forces.
  • The particles move closer together & bonds will start to form between the particles.
  • It turns into a liquid.

  
• As a liquid cools down:

  • The particles won't have enough energy to overcome the attraction between the molecules.
  • Even more bonds form
  • fixing the particles in place
  • freezing the liquid into a solid
• The Melting point:


  The temperature at which a solid converts into a liquid.
• The boiling point:


  The temperature at which a liquid converts into a gas.
• In a closed system:

  • changes in state won't change the mass at all
  • as the number of particles remains the same
  • however the density of the substance will change

  
• • current in the wire causes heating, increasing temp. of the metal wires / ice.

  Solid:

  • Arrangement of particles is regular
  • particle vibrate about a fixed position

  Melting:

  • Internal energy of the ice increases, increasing the temp. to melting point.
  • So as the temp. increases, particles vibrate faster
  • Eventually particles vibrate fast enough to break free from the strong bonds.
  • Therefore the arrangement of particles becomes irregular.

  Liquid:

  • arrangement of particles is irregular
  • particles movements is random.

  
• Cooling:

  • As the argon cools, the particles slow down
  • Particles in a liquid move slower than particles in a gas.
  • Particles in a solid move slower than particles in a liquid
  • as the liquid / solid cools, the particles get close together & the density increases.

  Gas to liquid:

  • Particles change from being spread apart to touching each other
  • particles will collide with other particles more often & change direction more often.

  
• Liquid to solid, Particles change from:

  • a random arrangement, to a regular pattern
  • moving freely to fixed positions & to vibrating.

  Because:

  • Internal energy of the argon decreases
  • Kinetic energy of the particles decreases with temp.
  • Potential energy of the particles change with change of state of the argon
  • zero Forces between particles in a gas
  • attractive forces act between atoms, when they're close to each other.
  • attractive forces between particles are stronger in a solid than a liquid.

  
• Solids:

  • Particles close together, so no room for particles to move closer, so hard to compress.

  • vibrate about fixed point.

  • strong forces of attraction at a distance.

  • particles strongly held together.

  not free to move around as shape is fixed.

  Gases:

  • Particles far apart

  • space between particles, so easy to compress

  • move randomly

  • No forces of attraction

  • spread out in all directions to fill the container