Particle Model, Density & Pressure
The kinetic particle model explains the properties of solids, liquids, and gases in terms of the arrangement, motion, and potential energy of their particles. Heating a substance increases its internal energy, either raising its temperature (governed by specific heat capacity) or changing its state at constant temperature (governed by specific latent heat).
- Density
- Mass divided by volume (ρ = m / V), measured in kg/m³.
- Internal Energy
- The total kinetic and potential energy of all the particles (atoms and molecules) that make up a system.
- Specific Latent Heat
- The amount of energy required to change the state of 1 kilogram of a substance with no change in temperature.
Particle Model, Density & Pressure: Wave Equation (v = fλ) & Force Vector (F = ma) Simulator
Adjust physical variables on the sliders below to see real-time changes in wave geometry, resultant forces, and acceleration.
F_net = 80 N − 25 N = 55 NAcceleration: a = F_net ÷ m = 55 ÷ 10 = 5.50 m/s²Key Concepts & Exam Definitions (5)
- Density
- Mass divided by volume (ρ = m / V), measured in kg/m³.
- Internal Energy
- The total kinetic and potential energy of all the particles (atoms and molecules) that make up a system.
- Specific Latent Heat
- The amount of energy required to change the state of 1 kilogram of a substance with no change in temperature.
- Sublimation
- The process where a solid turns directly into a gas without becoming a liquid.
- Gas Pressure
- The outward force exerted per unit area by gas particles colliding with the walls of a container.
Quick-Fire Flashcards (5)
Click any card to check the answer, then mark it as Known to track your progress.
What is the formula for calculating density?
In which state of matter are particles most closely packed?
What happens to the temperature of a substance while it is melting?
What causes gas pressure in a sealed container?
How does increasing temperature affect the pressure of a fixed volume of gas?
Exam-Style Questions & Mark Schemes (3)
Write or think through your answer first, then click Check Mark Scheme to see the exact points examiners award marks for.
- Q1
A block of aluminum has a mass of 54 kg and a volume of 0.02 m³. Calculate its density.
Click “Check Mark Scheme” to compare your answer, Density = 54 / 0.02 = 2700 kg/m³.
- Q2
Explain, using the particle model, why gases are easy to compress but solids are not.
Click “Check Mark Scheme” to compare your answer, In gases, there are large spaces between particles, so they can be pushed closer together. In solids, particles are already tightly packed and touching.
- Q3
Define specific latent heat of fusion.
Click “Check Mark Scheme” to compare your answer, The amount of energy required to change 1 kg of a substance from a solid to a liquid with no change in temperature.
Common Exam Questions (3)
What is density?
Density is the mass per unit volume of a substance, calculated using ρ = m ÷ V, where density ρ is in kg/m³, mass m is in kg, and volume V is in m³.
What is the difference between specific heat capacity and specific latent heat?
Specific heat capacity (c) is the energy required to raise the temperature of 1 kg of a substance by 1°C without changing state (ΔE = mcΔθ). Specific latent heat (L) is the energy required to change the state of 1 kg of a substance at constant temperature (E = mL).
How does gas pressure work?
Gas particles move rapidly in random directions and collide elastically with the inner walls of their container; each collision exerts a tiny force, and the total force per unit area over the container walls produces gas pressure.
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