Physics - particle model of matter

• Density

  Mass per unit volume
• Density equation

  mass/volume
• Particle arrangement of a solid

  - tightly packed in a regular arrangement

  - particles can only vibrate on the spot
• Particle arrangement of a liquid

  - close together with an irregular arrangement

  - can flow over each other
• Particle arrangement of a gas

  - separated with no regular arrangement

  - particles can move freely
• What is always the same when a substance undergoes a change of state?

  Mass
• How does a change of state differ from a chemical change

  In a change of state, the material can return to having its previous properties if the change is reversed.
• solid —> liquid

  melting
• liquid —> solid

  freezing
• gas —> liquid

  condensation
• liquid —> gas

  evaporation
• gas —> solid

  deposition
• solid —> gas

  sublimation
• What is internal energy

  the total kinetic and potential energy of all the particles that make up a system
• Pressure

  Force per unit area
• Pressure equation


  force/area
• How can you increase pressure?

  increase the number of particles

  increase the temperature
• Eureka can experiment

  1. The eureka can is filled with water until just below the spout and put a measuring cylinder under the can

  2. Tie the object to a string and slowly insert it into the water

  3. As the object fits into the can, the water it displaces pours out of the spout

  4. Measure the displaced water and will be the same volume as the object
• Movement of particles in a gas

  Move quickly in all directions and speeds
• Why can gas particles be compressed but solid particles can't?

  - The particles in a gas are widely spaced and move around freely

  - they will move to fit into any space

  - in solids the particles are more closely packed so cannot be compressed

  - no space for the solid to be compressed bc it's too dense