Density

• What are the three common states of matter?

  Solids, liquids, and gases
• How are particles arranged in solids, liquids, and gases?

  • Solids: Particles close together in a regular pattern
  • Liquids: Particles close together but not in a regular pattern
  • Gases: Particles far apart and not arranged in any pattern
• How do particles behave in a solid?

  They vibrate in a fixed position
• How do particles move in a liquid?

  They slide over each other
• How do particles move in a gas?

  They move very rapidly
• What does density tell us about a material?

  Mass for a given volume
• How is density calculated?

  Density = mass / volume
• What is the unit of density?

  Kilograms per meter cubed
• If a block of wood has a mass of 150 kg and a volume of $0.3 \text{ m}^3$, what is its density?


  $500 \text{ kg/m}^3$
• Why do solids usually have a high density?

  • Particles are tightly packed together
  • They have a lot of mass for their volume
• Why do liquids usually have a high density?

  • Particles are close together
  • They have a lot of mass for their volume
• Why do gases have a low density?

  • Particles are very far apart
  • They have a small mass for their volume
• What is an exception to the general rule of solid density?

  Polystyrene has a low density
• What is the structure of polystyrene under a microscope?

  • Contains air spaces
  • Has a very open structure