Final answer:
An extensive property of a substance is a physical property that depends on how much of the substance is present, such as mass and volume, which are directly proportional to the amount of matter.
Step-by-step explanation:
An extensive property of a substance is a physical property that depends on the amount of the substance. Examples include mass and volume. In contrast, intensive properties do not depend on the sample size. For instance, if you compare a gallon of milk to a cup of milk, the gallon will have a greater mass and volume because those are extensive properties directly proportional to the amount of matter present. Heat capacity is another extensive property because its value increases with the amount of the substance. On the other hand, the temperature of the two milk samples could be identical at 20 °C, demonstrating that temperature is an intensive property, not changing with the quantity of milk.