changes of state and particle model

• 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 is the order of states of matter from least to most dense?


  Gas, Liquid, Solid
• How are particles arranged in a solid?


  Particles are tightly packed in a regular arrangement and can only vibrate on the spot
• How are particles arranged in a liquid?


  Particles are close together but have an irregular arrangement and can flow over each other
• How are particles arranged in 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 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
• Why does the mass of a pan of water appear to decrease when water boils in an open pan?

  Some of the water evaporates and turns into water vapour, leaving the pan
• What happens to the mass of the whole system when water evaporates?


  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 condenses on the cooler mirror
• What happens to water vapour when it lands on a cooler mirror?


  The vapour condenses and returns to liquid state on the mirror’s surface