Units Used This Topic:
density kilogram/metre-cubed (kg/m3)
energy Joule (J)
mass kilogram (kg)
pressure Pascal (Pa)
specific heat capacity Joule/kilogram x degrees celsius (J/kg℃)
specific latent heat Joule/kilogram (J/kg)
temperature degrees celsius (℃)
volume metre-cubed (m3)
The particle model can be used to explain
- The different states of matter (solid, liquid, gas)
- Differences in density
The density (measured in kg/m3) of a material is defined by the equation:
density = mass / volume
Question: An iceberg has a mass of 11 200 kg
The volume of the iceberg is 12.0 m3
Calculate the density of the iceberg.
density = mass / volume
density = 11200 / 12
The density of the iceberg is 933 kg/m3
Question: The volume of a balloon is 0.014 m3
The density of the helium in the balloon is 0.180 kg/m3
Calculate the mass of helium in the balloon
density = mass / volume
0.18 = mass / 0.014
mass = 0.18 x 0.014
The mass is 0.00252kg
States of Matter
Solid
Particles are arranged in a regular pattern
Particles vibrate in a fixed position
Particles have strong forces between them
More dense than liquid & gas
Less energy than liquid & gas
Liquid
Particles are arranged in an irregular pattern
Particles move freely
Particles have weak forces between them
More dense than gas, less dense than solid
Less energy than gas, more energy then solid
Gas
Particles are in a constant, random motion with a range of speeds and directions
Particles have no forces between them
Less dense than liquid & gas
More energy than liquid & gas
The higher the temperature of the gas higher the average kinetic energy of the molecules of the gas.
When substances change state (melt, freeze, boil, evaporate, condense or sublimate), mass is conserved.
Changes of state are physical changes which differ from chemical changes because the material recovers its original properties if the change is reversed.
Question: Describe two ways the arrangement of particles in a solid is different from the arrangement of particles in a liquid. (3 marks)
- regular arrangement / pattern of particle in a solid
- particles are packed close(r) together in a solid
- particles in a fixed position in a solid
Question: Explain why heating a gas increases the average speed of the gas particles.
- heating increases the temperature of the gas
- temperature is proportional to kinetic energy
- if kinetic energy increases then the speed increases