3.1

• What is the definition of density?

  The mass per unit volume of a material
• What is the equation for density?

  $\rho =$$\frac{m}{v}$
• What are the units for density, mass, and volume?

  Density (kg/m³), Mass (kg), Volume (m³)
• What are the different states of matter in order of density of atoms?

  Gas, Liquid, Solid
• Describe the particle arrangement of a solid.

  Particles are tightly packed in a regular arrangement and can only vibrate on the spot.
• Describe the particle arrangement of a liquid.

  Particles are close together but have an irregular arrangement and can flow over each other.
• Describe the particle arrangement of a gas.

  Particles are separated with no regular arrangement and can move freely.
• What is always conserved 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.
• What is sublimation?

  When a solid changes into a gas without passing through a liquid state.
• What is evaporation?

  When a liquid changes into a gas state.
• What is the opposite of evaporation?

  Condensation, which is when a gas changes into a liquid state.
• When water boils in an open pan, why does the mass of the pan of water appear to decrease?

  Some of the water will evaporate and turn into water vapour, leaving the pan and decreasing its mass.
• What happens to the mass of the whole system when water boils in an open pan?

  The mass of the whole system remains constant.
• Explain the processes involved when a bathroom mirror mists up.

  Hot water evaporates to form water vapour, which lands on the cooler mirror and condenses back to liquid state on the mirror’s surface.
• What are the key characteristics of the particle arrangement in solids, liquids, and gases?

  • **Solid**: Tightly packed, regular arrangement, vibrate in place.
  • **Liquid**: Close together, irregular arrangement, can flow over each other.
  • **Gas**: Separated, no regular arrangement, move freely.
• What are the processes of state changes involving water?

  • **Sublimation**: Solid to gas without liquid.
  • **Evaporation**: Liquid to gas.
  • **Condensation**: Gas to liquid.