Particle Model of Matter

• Density is defined as the mass per unit volume of a substance.
• density (kg/m³) = mass (kg)/volume (m³)
• Density depends on the spacing of the atoms in matter.
• Mass is conserved during a change of state.
• Label the image

  A) mass

  B) density

  C) volume

  
• Density of a regular solid object:


  1. Use a balance to find the mass
  2. Measure its length, width & height and calculate volume
  3. Use the formula to find the object's density
• Density of a solid object:

  1. Use a balance to find the mass
  2. Submerge it in a Eureka can filled with water
  3. Let the displaced water transfer into a measuring cylinder to find the volume
  4. Use the formula to find the object's density
• Density of a liquid:

  1. Place a measuring cylinder on a balance, ensuing it is on zero
  2. Pour 10ml and record the liquids mass
  3. Repeat the process until the cylinder is full (recording the volume & mass each time)
  4. Use the formula to find the density for each recording (1ml = 1cm³)
  5. Take an average of the calculated densities
• Internal energy is the total kinetic and potential energy of the particles in a system.
• Internal energy is made of:

  • The kinetic energy that particles have due to their motion
  • The potential energy that particles have due to their position
• Internal energy does not include:

  • Gravitational potential energy
  • Kinetic energy caused by the whole substance
• When heating a substance we increase internal energy by:


  • Making the particles move by increasing temperature (kinetic energy increases)
  • It changes state (potential energy increases as particles move farther apart)
• A change of state is a physical reaction. This means that it is still the same substance but it has changed its form. This means mass is conserved.
• Specific latent heat is the energy required to change the state of 1kg of a substance with no change of temperature.
• energy (J) = mass (kg) x specific latent heat(J/kg)
• When a substance is melting of boiling, you're still putting in energy and increasing the internal energy. However, the energy is used to break bonds between particles rather than raising the temperature.
• When a substance is condensing or freezing, bonds are forming between particles, which releases energy. This decreases the internal energy, but doesn't decrease the temperature until all of the substance has turned to liquid or solid.
• The flat parts of the graph show energy transfer.