States of Matter

• Which theory attempts to explain the three states of matter:

  • particle theory
• The particle model (sometimes also called the kinetic model) has 3 main assumptions that particles are:

  • small
  • inelastic
  • spheres
• • In solids, strong attractive forces hold the particles in place, so that they can only vibrate in position. 
  • As the substance is heated, the particles gain energy and vibrate faster and faster. Eventually, the particles have so much energy that they can overcome the forces holding them together, and the substance melts into a liquid
• • As heat is applied to a liquid, the particles gain kinetic energy and move faster.
  • With enough energy they can break the forces of attraction between the molecules.
  • At this point the liquid would boil into a gas.
• • When a gas is heated, the particles gain kinetic energy and move faster
  • If the gas is trapped within a container that cannot expand, it means that the volume of the gas is fixed, and so the pressure inside the container increases
• • In gases, the particles have enough energy to overcome the attractive forces between them, and so spread out randomly. 
  • If the temperature is lowered, they will no longer be able to overcome these attractive forces, and the particles move closer together, and turn into a liquid
  • this is called condensation
• The temperature at which a solid converts into a liquid is called the melting point.
• The temperature at which a liquid converts into a gas is called the boiling point
• Strong forces of attraction between particles: solid
• Weak forces of attraction between particles: liquid
• Very weak forces of attraction between particles: gas
• • In a closed system, changes in state won't change the mass at all

  because the number of particles stay the same
• gases have the lowest density