Molecular Matter | Physics for GCSE/IGCSE - Year 11 PDF Download

Arrangement & Motion of Particles

In a solid

• Molecules are tightly packed and organized in a consistent structure.
• Molecules oscillate around fixed positions.

In a liquid

• Molecules remain close together without gaps but lack a uniform arrangement.
• Molecules can glide past each other.

In a gas

• Molecules are considerably spaced apart, approximately ten times farther in each direction.
• Molecules exhibit random movement at rapid velocities.

The Forces & Distances between Molecules

• The interactions among particles impact the state of matter. These interactions play a crucial role in determining the arrangement and movement of particles within a substance, influencing its properties such as shape, volume, and flow characteristics.
• The strength of these forces directly influences how particles behave in terms of their relative positions and movements. This, in turn, affects the substance's ability to undergo changes in shape, volume, and flow.
  • Changes in shape: The ability of a substance to alter its form without altering its volume.
  • Changes in volume: The capacity of a substance to occupy a specific amount of space.
  • Flow: The property of a substance to move or deform continuously under an applied force.
• Matter is composed of various types of particles, including atoms, molecules, ions, and electrons. These constituents collectively contribute to the properties and behavior of the substance.
  • Atoms: The basic units of matter, consisting of a nucleus surrounded by electrons.
  • Molecules: Combinations of atoms held together by chemical bonds.
  • Ions: Charged particles formed when atoms gain or lose electrons.
  • Electrons: Negatively charged subatomic particles orbiting the atomic nucleus.

Intermolecular Forces and Motion of Particles

Solids

• Molecules in solids are tightly bound by strong intermolecular forces, causing them to vibrate in place.
• The distance between molecules remains constant, giving the solid its rigid structure and fixed volume.

Liquids

• Molecules in liquids possess enough energy to surpass intermolecular forces, yet they remain closely packed.
• Liquid volume mirrors that of solids, but molecules can shift position by sliding past one another.
• This fluidity allows liquids to change shape and flow.

Gases

• Molecules in gases possess higher energy levels and move chaotically at rapid speeds.
• They have overcome the forces keeping them close, resulting in significant spaces between molecules.
• Gases can readily compress and expand, and they flow freely.

Temperature & Energy of Particles

• The pressure exerted by a gas on its container hinges on the gas's temperature.
  • This is because particles acquire kinetic energy with rising temperature.
• As the gas's temperature declines, so does the pressure on the container.
• In 1848, Lord Kelvin, a renowned Mathematician and Physicist, deduced the existence of a temperature at which gas particles cease exerting pressure.
  • At this temperature, they cease motion entirely, thus no longer colliding with their container.
• This temperature is termed absolute zero and measures -273 °C.

• The unit Kelvin is abbreviated as K.
  • It's important to note the absence of the degree symbol, unlike Celsius, which is represented as °C.