Kinetic Particle Model of Matter Notes

Kinetic Particle Model of Matter

States of Matter

  • The three states of matter are solid, liquid, and gas.

  • Solid: Has a fixed shape and volume.

  • Liquid: Has a fixed volume but takes the shape of its container.

  • Gas: Expands to completely fill a container.

Properties of Solids, Liquids, and Gases

  • Solids:

    • Definite shape and volume.

    • Cannot flow.

    • Not compressible.

  • Liquids:

    • No definite shape, but definite volume.

    • Can flow to take the shape of a container.

    • Not compressible.

  • Gases:

    • No definite shape or fixed volume.

    • Can flow and are highly compressible.

Changes of State

  • When a substance changes state, the number of molecules and mass remain constant; only the energy changes.

  • Changes of state are physical changes and are reversible.

  • Boiling: Liquid turns into a gas (evaporation).

  • Condensing: Gas turns into a liquid.

  • Melting: Solid turns into a liquid (e.g., ice to water).

  • Freezing: Liquid turns into a solid.

Arrangement & Motion of Particles

Properties of States of Matter

State

Density

Arrangement of particles

Movement of particles

Energy of particles

Solid

High

Regular pattern

Vibrate around a fixed position

Low energy

Liquid

Medium

Randomly arranged

Move around each other

Greater energy

Gas

Low

Randomly arranged

Move quickly in all directions

Highest energy

Intermolecular Forces and Motion

  • Intermolecular forces: Forces between separate molecules that hold the substance together (weaker).

  • Intramolecular forces: Strong forces within a molecule (stronger).

Solids

  • Molecules are held in place by strong intermolecular forces.

  • Vibrate in fixed positions.

  • Fixed and small distance between molecules gives solids their rigid shape and fixed volume.

Liquids

  • Molecules have enough energy to overcome some intermolecular forces.

  • Molecules are still held close together, maintaining volume.

  • Molecules slide past each other, allowing change of shape and flow.

Gases

  • Molecules have more energy and move randomly at high speeds.

  • Forces holding them together are overcome.

  • Large spaces between molecules allow easy compression and expansion.

  • Flow freely.

Temperature & Energy of Particles

  • As the temperature of a gas increases, so does the average speed of particles in the gas.

  • At higher temperatures, particles have more kinetic energy.

  • The pressure a gas exerts on its container depends on the temperature of the gas.

  • Particles gain kinetic energy as temperature increases.

Absolute Zero

  • There is a temperature at which particles are stationary.

  • This is the lowest possible temperature, as particles cannot travel slower than 0 m/s.

  • Absolute zero is the temperature at which all particles are stationary and is equal to -273°C.

Motion of Gas Particles

  • Random motion, colliding with container walls and other molecules.

  • Pressure in a gas is caused by the collisions of particles with the container walls.

  • When particles travel faster (at higher temperature), they collide with walls more frequently.

  • This means the gas exerts greater pressure.

Pressure and Force of Particles in a Gas

  • Pressure is defined as force per unit area.

  • P = {F {A}}, where:

    • P = pressure in Pascals (Pa)

    • F = force in newtons (N)

    • A = area in metres-squared (m^2)

  • Gas particles move randomly and collide with the walls of their containers.

  • These collisions produce force at right angles to the wall of the gas container (or any surface).

Brownian Motion

  • Random movement of particles in a liquid or gas, produced by large numbers of collisions with smaller particles, often too small to see.

  • Example: Smoke or pollen in a cylinder.

  • Light, fast-moving atoms and molecules collide with larger microscopic particles.

  • Brownian motion is observed in gases and liquids only.

Absolute Temperature

  • To convert between temperatures in Celsius (0°C) and Kelvin (T), use the following conversion:

    • Kelvin = 0C + 273

    • 0C = K - 273

The Gas Laws: Pressure and Volume (Constant Temperature)

  • If the temperature of a gas remains constant:

    • Compression (decreases volume) increases the pressure.

    • Expansion (increases volume) decreases the pressure.

    • P {V} = constant when T is constant.

  • A change in pressure can cause a change in volume.

Pressure & Temperature (Constant Volume)

  • Increasing temperature increases the pressure of a gas kept at a constant volume.

  • The average speed of molecules increases when the temperature increases (and vice versa).

  • More frequent collisions of gas molecules with the container wall as the particles have more energy increases the temperature.

    • P α T when V is constant.

Boyle’s Law

  • If the temperature T of an ideal gas is constant, then Boyle’s Law is given by:

    • P ∝ {1 {V}}

    • Pressure is inversely proportional to the volume of a gas.

    • PV = constant

  • The relationship between the pressure and volume for a fixed mass of gas at constant temperature can also be written as:

    • P1V1 = P2V2, where

      • P_1 = initial pressure (Pa)

      • P_2 = final pressure (Pa)

      • V_1 = initial volume (m^3)

      • V_2 = final volume (m^3$$)