P3 - Changes of state and particle model Flashcards
What is the definition of density? State
the relevant equation with units.
● The mass per unit volume of a material
● ⍴=m/v
● Density (kg/m³), Mass (kg), Volume (m³)
State the different states of matter in order (least to
most) of the density of atoms.
● Least dense: Gas
● Liquid
● Most dense: Solid
Describe the particle arrangement of a
solid.
Tightly packed in a regular arrangement.
Particles can only vibrate about their fixed positions.
Describe the particle arrangement of a
liquid.
Close together, but with an irregular arrangement. They can flow over each
other.
Random directions, low speeds
Describe the particle arrangement of a
gas.
Separated, with no regular arrangement.
Particles can move freely.
Particles move at random speeds in random directions.
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. This will leave the pan
meaning the mass of the pan will decrease.
The mass of the whole system however remains constant.
Explain the processes involved when a bathroom mirror mists up.
● Hot water evaporates to form water vapour
● This water vapour lands on the cooler
mirror
● The vapour condenses and returns to liquid
state on the mirror’s surface
