Describe the difference between intensive and extensive properties. Which of the following properties are intensive: (a) mass: (b) density; (c) volume; (d) melting point?
The Correct Answer and Explanation is:
The correct answer is that (b) density and (d) melting point are intensive properties.
In the study of matter, physical properties are categorized into two main types: intensive and extensive. The distinction between them is based on whether the property depends on the amount of substance present.
Extensive properties are those that depend on the quantity or size of the sample. These properties are additive; if a system is divided into parts, the value of the extensive property for the whole system is the sum of the values for its parts. For example, mass is an extensive property because the mass of an object is directly proportional to the amount of matter it contains. A 20-gram block of iron has twice the mass of a 10-gram block. Similarly, volume is extensive because it measures the amount of space a substance occupies. Combining two liters of water results in a total volume of four liters.
In contrast, intensive properties are independent of the amount of substance. They are intrinsic characteristics of the material itself. No matter how much or how little of a substance is present, an intensive property remains the same. For instance, the melting point of water is 0°C (at standard pressure). This temperature is the same for a small ice cube as it is for a giant iceberg; it is a fundamental characteristic of water, not its quantity. Likewise, density, which is the ratio of mass to volume (mass/volume), is an intensive property. While both mass and volume are extensive, their ratio is constant for a given substance. A single drop of water and a swimming pool full of water have the same density. Dividing a sample in half will halve its mass and its volume, but their ratio—the density—remains unchanged.
