The Particle Model of Matter: States, Density and Energy Changes
The Particle Model of Matter States of Matter Matter exists in three fundamental states: solid, liquid, and gas. These states arise from the arrangement and mov...
The Particle Model of Matter
States of Matter
Matter exists in three fundamental states: solid, liquid, and gas. These states arise from the arrangement and movement of particles:
Solids: Particles are closely packed in a regular pattern, vibrating about fixed positions. Solids have a definite shape and volume.
Liquids: Particles are randomly arranged but still closely packed, able to slide over each other. Liquids have a definite volume but take the shape of their container.
Gases: Particles are widely spaced apart, moving randomly in all directions. Gases have no definite shape or volume, expanding to fill their container.
Density
Density is a measure of mass per unit volume. It can be calculated as:
density = mass / volume
Worked Example
Problem: A block of aluminum with a mass of 540 g has a volume of 200 cm³. Calculate its density.
Solution:
mass = 540 g = 0.54 kg
volume = 200 cm³ = 2 x 10⁻⁴ m³
density = mass / volume = 0.54 kg / (2 x 10⁻⁴ m³) = 2700 kg/m³
Internal Energy
Internal energy is the total kinetic and potential energy of all particles within a substance. Heating increases internal energy by:
Increasing particle kinetic energy, raising temperature
Causing a change of state by overcoming intermolecular forces
Specific heat capacity (c) is the energy needed to raise 1 kg of a substance by 1°C. Specific latent heat (L) is the energy needed for 1 kg of a substance to change state.
Energy change = mc(Δt) for heating/cooling or E = mL for state changes
Gas Laws
For a fixed mass of gas:
Increasing temperature increases particle kinetic energy and impact force, increasing pressure.