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P2.1.1P2. Thermal Physics

States of matter — Combined Science 0653 - Physics Revision Notes & Topical Questions

5 min read 8 parts Lesson 2 of 14 1 quiz

📚 Combined Science 0653 - Physics Hub / Topical Revision
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Lesson summary

P2.1.1 States of matter — COMBINED SCIENCE notes: Describe the properties of solids, liquids and gases and the changes of state between them.Shape — a solid has a definite shape.Volume — a solid has a definite volume.Flow and compression — a solid cannot flow and cannot be compre…

  • Shape and volume
  • Freezing (solidification)
  • Boiling (vaporising)
  • Condensing
  • Physical change
  • Fixed temperature

Part 1 of 7Solids

1Shape
  • Shape a solid has a definite shape.
2Volume
  • Volume a solid has a definite volume.
3Flow and compression
  • Flow and compression a solid cannot flow and cannot be compressed.

Part 2 of 7Liquids

1Shape
  • Shape a liquid has no definite shape and takes the shape of its container.
2Volume
  • Volume a liquid has a definite volume.
3Flow and compression
  • Flow and compression a liquid flows but cannot be compressed.

Part 3 of 7Gases

1Shape and volume
  • Shape and volume a gas has neither a definite shape nor a definite volume, so it fills its container.
2Flow and compression
  • Flow and compression a gas flows freely and is easily compressed.

Part 4 of 7Summary of the three states

PropertySolidLiquidGas
ShapeFixedTakes the shape of the containerFills the container
VolumeFixedFixedNot fixed
FlowsNoYesYes
CompressibleNoNoYes
DensityHighMediumLow

Part 5 of 7Changes of state

1Melting
  • Melting a solid turns into a liquid.
2Freezing (solidification)
  • Freezing (solidification) a liquid turns into a solid.
3Boiling (vaporising)
  • Boiling (vaporising) a liquid turns into a gas.
4Condensing
  • Condensing a gas turns into a liquid.

Part 6 of 7What changes and what stays the same

Mass
  • Mass it stays the same because the number of particles does not change.
Energy
  • Energy the energy of the particles is what changes.
Physical change
  • Physical change changes of state are reversible and no new substance forms.
Fixed temperature
  • Fixed temperature during melting and boiling the temperature stays constant because the energy supplied changes the arrangement of the particles instead of raising their kinetic energy.
Pure water
  • Pure water it melts at 0 °C and boils at 100 °C at standard atmospheric pressure.

Part 7 of 7More from the specification

More from the specification
Intermolecular electrostatic forces
  • Intermolecular electrostatic forces microscopic attractive forces between neighboring particles dictate transition temperatures between solid, liquid,
    • and gaseous phases.
Kinetic particle model
  • Solids have particles in fixed positions vibrating, liquids have closely packed particles moving past each other,
  • and gases have widely spaced particles in rapid random motion.
Brownian motion
  • The random, jerky movement of visible smoke or pollen particles shows they are bombarded by fast, invisible molecules colliding randomly.
Gas pressure
  • Pressure is caused by molecules colliding with the walls of a container,
  • so increased temperature increases both their speed and force of collisions,
  • increasing pressure.
Kelvin scale
  • Absolute temperature in kelvin equals Celsius plus 273, with absolute zero at 0 K where molecular motion is at a minimum.
Gas laws
  • At constant temperature pV is constant, and at constant volume pressure is proportional to absolute temperature.
Brownian motion
  • The random movement of particles.
Inversely proportional
  • When one quantity doubles, the other halves.
Average speed
  • Total distance travelled divided by total time taken.
Molecule
  • Two or more atoms joined together chemically.
Kelvin
  • The SI unit of absolute temperature.
Collision
  • Particles hitting each other.
Force
  • A push or pull on an object caused by an interaction with another object.
p1V1
p1V1 p2V2
What the symbols mean: p1, V1 = pressure and volume before · p2, V2 = after; only for a fixed mass of gas at constant temperature

Key terms

TermMeaning
SolidA state of matter with a fixed shape and fixed volume.
LiquidA state of matter with a fixed volume that takes the shape of its container.
GasA state of matter that fills its container and is easily compressed.
MeltingThe change from solid to liquid.
FreezingThe change from liquid to solid.
BoilingThe change from liquid to gas.
CondensingThe change from gas to liquid.

Avoid these mistakes

1
Saying liquids can be compressed easily — liquids are almost incompressible, only gases are easily compressed.
2
Saying mass changes when a substance melts or boils — the number of particles is the same, so the mass is unchanged.
3
Saying the temperature rises during melting — it stays constant until the change is complete.
4
Saying a liquid has a fixed shape — a liquid has a fixed volume but takes the shape of its container.

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