Particle Model of Matter
Ever wondered why a rock stays solid whilst water flows freely? It's all about how particles are arranged and the forces between them. Solids have particles packed tightly together with strong intermolecular bonds, keeping them vibrating in fixed positions with a fixed volume.
Liquids are more relaxed - their particles have weaker forces between them, allowing them to move past each other in random directions at low speeds. This is why you can pour water but not a brick!
Gases are the rebels of the particle world. With no forces of attraction between particles, they move freely in random directions at random speeds. When gas particles collide with container walls, they create pressure - which is simply force per unit area.
Key insight: Higher temperature means faster-moving particles, leading to more frequent collisions and higher pressure. This is why aerosol cans explode in heat!
Density tells you how tightly packed particles are in a given space. Use the formula: ρ = mass ÷ volume. For practical measurements, weigh solids before and after water displacement, or measure liquid mass in 10ml increments for accuracy.
