← Workshop GCSE Particle Model of Matter

GCSE Particle Model ⚛️

Everything you need to know about particles, states of matter, and gases — interactive, visual, and with just enough humour to stay awake.

AQA / Edexcel · Particle physics for people who prefer sleeping

🧊 States of Matter

Solid, liquid, gas. The difference is how much the particles care about personal space.

💬 "Solid, liquid, gas. In a solid they're holding hands in a mosh pit. In a liquid they're jostling at a party. In a gas they've gone full ghost and filled the room."
SOLID
LIQUID
GAS
Solid
Particles vibrate in fixed positions. Very close together. Strong forces between them. Regular arrangement. Cannot flow. Fixed shape AND volume.
Liquid
Particles move freely but stay close. Weaker forces. No fixed shape — fills container. Fixed volume. Can flow. Random arrangement.
Gas
Particles move fast and randomly, spread out. Very weak/no forces. No fixed shape or volume. Fills any container completely.

⚖️ Density

How much stuff is packed into a space. More stuff = more dense.

💬 "Density is why a small block of gold is heavier than a big block of wood. It's not magic, it's just more stuff squeezed in. Gold particles are not only expensive — they're also antisocially close together."
ρ = m ÷ V
Density (kg/m³) = Mass (kg) ÷ Volume (m³)
1000 kg/m³
Material Densities (kg/m³)

🔥 Changes of State

When you heat something up, it doesn't always get hotter. Sometimes it just changes state.

💬 "The heating curve has two flat bits. That's where your energy is going in but the temperature isn't rising. The particles are too busy breaking free of each other to get any hotter. Relatable."
Solid heating Melting (flat — latent heat) Liquid heating Boiling (flat — latent heat) Gas heating
Melting Point — temperature stays constant as solid → liquid. Energy breaks bonds, not speeding up particles.
Boiling Point — temperature stays constant as liquid → gas. Again, energy breaks bonds first.

❄️ Specific Latent Heat

Energy absorbed or released during a change of state — with no temperature change.

💬 "Boiling water takes 7× more energy than melting ice of the same mass. Latent heat of vaporisation is massive. This is why burns from steam are worse than boiling water — the steam dumps ALL that extra energy into you when it condenses. Ouch."
E = m × L
Energy (J) = Mass (kg) × Specific Latent Heat (J/kg)
Material L value (J/kg):
334,000 J
Sweating works because of latent heat of vaporisation. Water evaporating from your skin takes energy WITH it — cooling you down. Your body weaponises thermodynamics.

⚡ Internal Energy

The total energy stored in all the particles of a substance — KE plus PE.

💬 "Temperature is not the same as internal energy. Temperature is the average KE of particles. Internal energy is the total of ALL their kinetic AND potential energy. A hot cup of tea has more internal energy than a cold swimming pool — but the pool has more total internal energy. Mass matters."
50%
Kinetic Energy (KE)
50%
Potential Energy (PE)
100%
Internal Energy (Total)
Kinetic Energy — energy of particles moving. Higher temperature = faster particles = more KE. Temperature measures average KE.
Potential Energy — energy in the bonds/positions between particles. During state changes, PE changes but KE (temperature) stays the same.

💨 Gas Pressure & Particle Collisions

Pressure is just particles hitting the walls. More hits, harder hits = more pressure.

💬 "Gas pressure is democracy in action. Millions of tiny particles all collectively smashing into walls. The wall doesn't know any individual particle — it just feels the total force. P = F ÷ A. That's it."
1.0×
Particle Speed
Moderate
Collision Frequency
1.0 P
Relative Pressure
P ∝ T
At constant volume: Pressure ∝ Absolute Temperature (K). Double T → double P.
P = F ÷ A
Pressure (Pa) = Force (N) ÷ Area (m²)

🔵 Boyle's Law — Pressure & Volume

Squeeze the gas → less space → more wall hits → higher pressure.

💬 "Boyle's Law: P₁V₁ = P₂V₂. Halve the volume, double the pressure. This is why a bicycle pump gets harder to push as you compress it, and why syringes feel stiffer when you block the end. You're literally squeezing particles into a smaller argument."
P₁V₁ = P₂V₂
At constant temperature. Pressure × Volume = constant.
1.0 P₀
Pressure
100%
Volume
100
P×V (constant)
P vs V — inverse (hyperbola). Moving dot = current state.
Bicycle pump — compress air in barrel, pressure rises as volume shrinks. Harder to push at the end.
Syringe with blocked end — push plunger, volume drops, pressure rises, plunger resists. Classic exam practical.

🌡️ Temperature & Absolute Zero

There is a coldest possible temperature. It's −273°C. And nobody's ever actually reached it.

💬 "Absolute zero is −273°C. Nothing can get colder. It's the universe's lowest possible temperature setting, and physicists have got within a fraction of a degree of it — but never actually reached it. It's the most exclusive temperature in existence."
K = °C + 273
Kelvin = Celsius + 273. Absolute zero = 0 K = −273°C
20
Celsius (°C)
293
Kelvin (K)
Active
Particle motion
Why Kelvin?
Gas laws only work with Kelvin. At 0 K particles have minimum energy. At 0°C they still move — that's 273 K, not zero energy. Always convert °C → K for gas law calculations.
Key temperatures:
Absolute zero: 0 K = −273°C
Ice melting: 273 K = 0°C
Body temp: 310 K = 37°C
Water boils: 373 K = 100°C
Pressure vs Temperature — extrapolates to 0 K at zero pressure

🎲 Brownian Motion

A large particle jostled randomly by invisible smaller ones. Einstein proved atoms exist this way.

💬 "In 1905, Einstein published 4 world-changing papers. One explained Brownian motion. Another was special relativity. He was having a productive year. Meanwhile Robert Brown had watched pollen jiggle in water under a microscope in 1827 and thought it was alive. Einstein proved it was atoms."
What you see: Large pollen/dust particle moves in a random, jerky path. This is because invisible molecules hit it from all sides — but not equally at every moment.
What it proves: Atoms and molecules exist and are in constant random motion. Higher temperature → faster molecules → more chaotic path.
Historical significance (exam favourite): Einstein's 1905 mathematical explanation of Brownian motion provided the first solid evidence that matter is made of discrete atoms. Before this, the existence of atoms was still debated by some scientists.

✅ Quiz — Test Yourself

5 questions. No cheating. Your future self will thank you.

1. A block of material has a mass of 2700 kg and a volume of 1 m³. What is its density?

ρ = m ÷ V = 2700 ÷ 1 = 2700 kg/m³. This is roughly the density of aluminium. ✅

2. During melting, energy is being added to a substance. What happens to the temperature?

Temperature stays CONSTANT during melting. The energy input goes into breaking bonds (increasing PE), not increasing kinetic energy (temperature). This is latent heat. ✅

3. How much energy is needed to melt 2 kg of ice? (Specific latent heat of fusion of water = 334,000 J/kg)

E = m × L = 2 × 334,000 = 668,000 J. Double the mass, double the energy needed. ✅

4. A gas at pressure 200 kPa has volume 3 m³. What is the pressure when volume is compressed to 1 m³ (temperature constant)?

P₁V₁ = P₂V₂ → 200 × 3 = P₂ × 1 → P₂ = 600 kPa. Boyle's Law: halve the volume, double the pressure. A third of the volume = triple the pressure. ✅

5. What temperature in Kelvin corresponds to absolute zero?

Absolute zero = 0 K = −273°C. The Kelvin scale starts at absolute zero, so 0 K IS absolute zero by definition. ✅

⚛️ Equations

ρ = m ÷ VDensity = Mass ÷ Volume (kg/m³)
E = m × LEnergy = Mass × Specific Latent Heat (J)
P₁V₁ = P₂V₂Boyle's Law — constant temperature
K = °C + 273Kelvin = Celsius + 273
P = F ÷ APressure = Force ÷ Area (Pa)
P ∝ TPressure ∝ Absolute Temp (constant V)
🤖 BTH Tutor — Particles
Hi! I'm your particle model tutor. Ask me anything about states of matter, density, latent heat, gas laws, or absolute zero. 🧊💨🔥
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GCSE Physics Revision Suite • 5 of 9 • Paper 1