Problem 17 - Chemistry The Molecular Nature of Matter

Question

Determine whether each of the following is an intensive or extensive property, and justify your reasoning: (a) mass (e) physical state (b) boiling point (f) density (c) color (g) volume (d) surface area

Step-by-Step Solution

Answer

Mass, volume, and surface area are extensive properties. Physical state, boiling point, density, and color are intensive properties.

Step 1: Identifying Intensive and Extensive Properties

Intensive properties are those that do not depend on the amount of the substance present. Extensive properties are those that do depend on the amount of the substance present.

Step 2: Analyze Mass

Mass is an extensive property because it depends on the quantity of the substance present.

Step 3: Analyze Physical State

Physical state is an intensive property because it does not depend on the amount of substance; a small and large sample of water will both be liquid at room temperature.

Step 4: Analyze Boiling Point

Boiling point is an intensive property because it is a characteristic of the substance itself and does not change with the amount of the substance.

Step 5: Analyze Density

Density is an intensive property because it is defined as mass per unit volume and does not depend on the amount of the substance.

Step 6: Analyze Color

Color is an intensive property because it does not depend on the size or quantity of the substance; a small and large piece of gold both exhibit the same color.

Step 7: Analyze Volume

Volume is an extensive property because it depends on the quantity of the substance present.

Step 8: Analyze Surface Area

Surface area is an extensive property because it depends on the size of the sample of the substance.

Key Concepts

Mass as Extensive Property

When we explore the properties of a material, we classify them to better understand how they might change under different circumstances. One such property is mass, an extensive property, meaning it is dependent on the quantity of the substance in question.

Think of mass in the same way you might think of the weight of ingredients when you’re baking a cake. The more flour or sugar you add, the greater the mass of the cake. Likewise, if you have two identical cars, one fully assembled and the other disassembled into multiple pieces, the total mass of both is the same, but the distribution of mass across the disassembled parts varies. This illustrates the principle of extensivity: the mass of an object or system is the sum of the masses of its components and changes with the amount of matter.

Understanding that mass is extensive is crucial in fields like chemistry or material science, where reactions and properties depend on the amounts of substances involved.

Boiling Point as Intensive Property

When we boil water, we know it turns to steam at 100°C (212°F) at sea level, regardless of whether we're heating a cup or a full pot. This is because the boiling point is an intensive property; it does not depend on the amount of the substance present.

Intensive properties are intrinsic to the material. For example, pure gold melts at the same temperature regardless of whether you have a tiny flake or a large bar. The reason properties like boiling point are so important is due to their role in identifying substances and predicting their behavior. Knowing the boiling point can help predict how a substance will react under heat, which is key to applications ranging from culinary arts to industrial chemical processes.

Density as Intensive Property

Much like the boiling point, density is an intensive property that remains the same regardless of the sample size. Density is a measure of how much mass is contained in a given volume. To understand density, imagine two balls, one made of lead and the other of the same size but made of foam. The lead ball is much heavier because it has more mass in the same volume, showcasing a higher density.

Density is critical when determining if something will float on water, for example, or for identifying substances. It’s a particularly useful property in materials science and engineering, where the strength and weight of materials are vital to the integrity of a structure. When you grasp that the density of a substance stays consistent no matter how much you have, it opens up predictive possibilities in both scientific research and everyday problem-solving.