3. Particle Model of Matter

• DENSITY


  A measure that compares a substance's MASS to the VOLUME it occupies
• DENSE material


  Particles are close together
• If a material is compressed


  The particles are forced closer, increasing the DENSITY
• Units of Density


  Kilograms per cubic meter (kg/m³) or grams per cubic centimeter (g/cm³)
• Density practical for regular objects


  Measure length, width, height to calculate volume, use mass balance to determine mass, apply density equation
• Density practical for irregular objects


  Measure mass, use displacement technique to find volume, apply density equation
• PARTICLE MODEL of matter


  Helps explain the three states of matter: solid, liquid, and gas
• SOLIDS


  • Particles are tightly packed in a FIXED, REGULAR PATTERN with strong forces between them, giving solids a DEFINITE SHAPE and VOLUME
• LIQUIDS


  • Particles are close but can move past each other due to WEAKER FORCES of attraction, allowing liquids to flow and take the shape of their container while maintaining a CONSTANT VOLUME
• GASES


  • Particles move freely at high speeds due to VERY WEAK OR NO FORCES, allowing gases to expand to fill their container
• Measuring the volume of an object

  1. Place the object in the Eureka can

  2. The water displaced will pour into the measuring cylinder

  3. The volume of water displaced and collected in the measuring cylinder equals the volume of the object
• Density


  Calculated using the mass and volume of an object in the density equation
• States of matter


  Solid, liquid, and gas
• Particle model of matter


  • Solids: Particles are tightly packed in a fixed, regular pattern with strong forces between them
  • Liquids: Particles are close but can move past each other due to weaker forces of attraction
  • Gases: Particles move freely at high speeds due to very weak or no forces of attraction between them
• Density differences


  Solids are the most dense, liquids are less dense, and gases are the least dense
• Changes of state


  1. Melting

  2. Freezing

  3. Boiling

  4. Condensing

  5. Sublimating
• Changes of state are physical changes which differ from chemical changes because the material recovers its original properties if the change is reversed
• Internal energy


  The total energy that particles in a system have from their movement and position
• Internal energy


  • Kinetic energy stores: Due to the vibration or movement of particles
  • Potential energy stores: Due to the position of particles within the system
• Heating a system


  Increases its internal energy
• Change in temperature


  Can lead to a change in state
• Latent heat


  The energy required for a substance to change its state
• Specific latent heat


  The amount of energy required to change the state of 1kg of a substance with no change in temperature
• Specific heat capacity


  The amount of heat energy required to raise the temperature of 1 kilogram of a substance by 1 degree Celsius without changing its state
• Specific latent heat


  The amount of heat energy needed to change the state of 1 kilogram of a substance without changing its temperature
• Heating and cooling graphs


  • Depict the relationship between temperature and time as a substance changes state
  • Show the points at which changes of state occur
• Particle motion in gases

  Gases consist of a large number of small particles in constant random motion, moving in straight lines until they collide
• Increasing temperature of a gas


  Increases the speed of its molecules
• Pressure in a gas


  The result of collisions between gas molecules and the container walls
• Increasing temperature of a gas at constant volume

  Increases the pressure