• When a substance changes state, the number of molecules in that substance doesn’t change and so neither does its mass
  • The only thing that changes is its?energy

   

• Unlike chemical changes, changes of state (a type of physical change) are?reversible

• In a?solid:
  • The molecules are very?close?together and arranged in a?regular?pattern
  • The molecules?vibrate?about fixed positions

   

• In a?liquid:
  • The molecules are still?close?together (no gaps) but are no longer arranged in a regular pattern
  • The molecules are able to?slide past each other

   

• In a?gas:
  • The molecules are?widely separated?- about 10 times further apart in each direction
  • The molecules move about?randomly at high speeds

   

• There are six changes of state that can occur between solids, liquids and gases:
  • Melting?- When a solid turns into a liquid (e.g. ice to water)
  • Boiling?- When a liquid turns into a gas (evaporating)
  • Condensing?- When a gas turns into a liquid
  • Freezing?- When a liquid turns into a solid
  • Subliming?-When a solid turns into a gas

   

Diagram showing the arrangement and motion of different states of matter?

• Heating a system will change the energy stored in a system by?increasing the kinetic energy?of its particles
  • The?temperature?of the material, therefore, is related to the average kinetic energy of the molecules

   

• This increase in kinetic energy (and therefore energy stored in the system) can:
  • Cause the?temperature?of the system to increase
  • Or, produce a?change of state?(solid to liquid or liquid to gas)

   

• The higher the temperature, the higher the average kinetic energy of the molecules and vice versa
  • This means they move around?faster

   

As the container is heated up, the gas molecules move faster with higher kinetic energy. The energy stored within the system - the internal energy - therefore increases

ANSWER:? ?D

• • A?is?true?because the mass lost from the beaker is due to those water molecules evaporating
  • B?is?true?because evaporation causes the most energetic particles to leave the beaker
    • The total number of particles in the beaker decreased

     

  • C?is?true?because additional water molecules were added to the air, without a significant change in the volume of the air
  • D?is?not true?because no mass is lost during evaporation - it is only changed from a liquid to gas state