Chemistry · Thermodynamics · NEET
| Depends on amount of matter? | Yes — value changes with size/quantity | No — value is independent of quantity |
| Split test (halve the system) | Value becomes half | Value stays the same |
| Examples | Mass, volume, internal energy, enthalpy, entropy, heat capacity | Temperature, pressure, density, molar volume, specific heat |
| How to make one from the other | Sum of parts adds up | Ratio of two extensive properties (X/n or mass/volume) |
| NEET scaling in thermochemistry | Multiply/reverse changes the value (Delta H, Delta S) | Value does not change on scaling (T, P) |
Do the split test. Imagine dividing the system into two equal halves. If the value of the property also becomes half, it is extensive (like volume or mass). If the value stays the same in each half, it is intensive (like temperature or density). NCERT uses this exact idea: split a gas container in two, each half has volume V/2 (extensive) but the same temperature T (intensive).
Enthalpy (H) is EXTENSIVE. If you double the amount of substance, the total enthalpy doubles. This is why NEET reaction enthalpy values are written 'per mole' and why you multiply Delta H when you scale up a thermochemical equation. NCERT clearly lists internal energy and enthalpy as extensive properties.
Density is INTENSIVE. This confuses many students. Mass is extensive and volume is extensive, but density = mass/volume. When you take half the sample, mass becomes half AND volume becomes half, so density = (half mass)/(half volume) stays the SAME. A ratio of two extensive properties for the same substance is intensive. That is the key rule.
Heat capacity (C) is EXTENSIVE. More matter needs more heat to raise its temperature by 1 kelvin, so C depends on amount. But molar heat capacity (Cm) and specific heat capacity are INTENSIVE, because they are 'per mole' or 'per gram' — the amount has already been divided out.
Temperature measures the average energy of the particles, not the total amount, so it does not change if you add more of the same matter at the same conditions — intensive. Heat capacity measures how much total heat the whole system needs, so more matter needs more heat — extensive. Temperature is an intensity; heat capacity is a total amount.
A molar property is an extensive property divided by the number of moles: Xm = X/n. Dividing an extensive quantity by the amount (n) cancels the dependence on size, so every molar property is intensive. Examples: molar volume Vm and molar heat capacity Cm. The next concept explains this in detail.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Extensive (depend on amount): mass, volume, internal energy (U), enthalpy (H), entropy (S), Gibbs energy (G), heat capacity (C), number of moles. Intensive (do not depend on amount): temperature, pressure, density, concentration, molar volume, molar heat capacity, specific heat, viscosity, refractive index, boiling point, melting point.
Pressure is INTENSIVE. If you split a gas container into two equal parts at equilibrium, each part has the same pressure, so pressure does not depend on the amount of matter.
Yes. Internal energy (U), enthalpy (H) and entropy (S) are all extensive. Their values scale with the amount of substance, which is why NEET numerical answers are given per mole.
Because you must know which quantities to scale when you multiply or reverse a thermochemical equation. Extensive quantities (Delta H, Delta U, Delta S) get multiplied by the same factor as the equation; intensive quantities (T, P) do not change. Mixing this up causes wrong answers in enthalpy and entropy problems.
Yes. Dividing one extensive property by another (or by amount n) gives an intensive property. Density = mass/volume, molar volume = V/n, and molar heat capacity = C/n are all intensive because the amount cancels out.
