Matter exists in three states - solids, liquids, and gases...
Physics212 views·Updated 27 Aug 2026·2 pagesGCSE Physics: Master Topic 3 - The Particle Model of Matter
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Patrick k@patrick07
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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.
2
of 2
Internal Energy and State Changes
Think of internal energy as the total energy bank account of all particles - it includes both their movement (kinetic) and position (potential) energy stores. When you heat something, you're essentially making deposits into this energy account.
Here's where it gets interesting: during state changes like melting or boiling, temperature stays constant even though you're adding energy. This energy goes into breaking intermolecular bonds rather than making particles move faster - it's called latent heat.
Specific latent heat is the energy needed to change 1kg of substance from one state to another without changing temperature. There are two types: fusion (solid to liquid) and vaporisation (liquid to gas). The formula is simple: Energy = mass × specific latent heat.
Remember this: Mass never disappears during state changes - 1kg of ice becomes exactly 1kg of water, then 1kg of steam. Only the arrangement changes, not the amount of matter.
On heating graphs, look for flat horizontal lines - these show where state changes occur whilst temperature remains constant.
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Physics212 views·Updated 27 Aug 2026·2 pagesGCSE Physics: Master Topic 3 - The Particle Model of Matter
P
Patrick k@patrick07
Matter exists in three states - solids, liquids, and gases - and understanding how particles behave in each state is crucial for grasping physics concepts. The particle model explains everything from why ice melts to how pressure cookers work, making...
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of 2
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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.
2
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Internal Energy and State Changes
Think of internal energy as the total energy bank account of all particles - it includes both their movement (kinetic) and position (potential) energy stores. When you heat something, you're essentially making deposits into this energy account.
Here's where it gets interesting: during state changes like melting or boiling, temperature stays constant even though you're adding energy. This energy goes into breaking intermolecular bonds rather than making particles move faster - it's called latent heat.
Specific latent heat is the energy needed to change 1kg of substance from one state to another without changing temperature. There are two types: fusion (solid to liquid) and vaporisation (liquid to gas). The formula is simple: Energy = mass × specific latent heat.
Remember this: Mass never disappears during state changes - 1kg of ice becomes exactly 1kg of water, then 1kg of steam. Only the arrangement changes, not the amount of matter.
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Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
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