Chemistry · Thermodynamics · NEET
An intensive property is any property whose value stays the same even if you change the amount (mass or size) of the substance. It does not add up when you combine two parts. Temperature, pressure and density are the standard NCERT examples. This matters for NEET because questions often ask you to sort a list into intensive and extensive.
Take a gas in a container at temperature T. If you put a partition in the middle so each half has volume V/2, the temperature of each half is STILL T, not T/2. The temperature did not split. Because the value does not depend on the amount, temperature is intensive. This exact example is in your NCERT (Fig 5.6).
Density = mass / volume. Mass is extensive and volume is extensive. But when you divide one extensive quantity by another, the 'amount' part cancels out. If you cut a block of iron in half, both the mass and the volume become half, so density (mass/volume) stays the same. A ratio of two extensive properties is intensive.
Pressure is intensive. In a container of gas at pressure p, if you imagine a partition splitting the volume, each side is still at the same pressure p. The pressure does not get shared or divided by size. So pressure does not depend on the amount of gas and is intensive.
A molar property is an extensive property divided by the number of moles (n). For example molar volume Vm = V/n and molar heat capacity Cm = C/n. Dividing by n removes the dependence on amount, so a molar property becomes intensive. This is a common NEET trick: 'volume is extensive, but molar volume is intensive.'
Ask one question: 'If I take just half of the sample, does this value change?' If the value stays the same (like temperature, pressure, density), it is intensive. If the value becomes half (like mass, volume, enthalpy), it is extensive. Also remember: any ratio of two extensive properties (like density or molar volume) is intensive.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
NCERT lists temperature, density and pressure as intensive properties. Molar properties (like molar volume and molar heat capacity) are also intensive because dividing by moles removes the dependence on amount.
Temperature is intensive. If you split a sample into two parts, each part keeps the same temperature; the value does not depend on how much matter is present.
Density is intensive. It is mass divided by volume, and both change by the same factor when the amount changes, so the ratio stays fixed.
Molar properties are intensive. A molar property is an extensive property divided by the number of moles (n), and this division removes the dependence on amount.
NEET often gives a list of properties and asks you to classify them. Knowing that temperature, pressure and density are intensive, while mass, volume and enthalpy are extensive, lets you answer these quickly and avoid the density trap.
