Problem 26 - Chemistry Principles and Practice

Question

Each of the following parts contains an underlined property. Classify the property as intensive or extensive and as chemical or physical. (a) A lemon is yellow. (b) Sulfuric acid converts sugar to carbon and steam. (c) The sample has a mass of \(1 \mathrm{~kg}\). (d) Sand is insoluble in water. (e) Wood burns in air, forming carbon dioxide and water.

Step-by-Step Solution

Answer

(a) Intensive physical; (b) Chemical; (c) Extensive physical; (d) Intensive physical; (e) Chemical.

Step 1: Analyze Part (a) - A lemon is yellow

The color of a lemon being yellow is an appearance-based property of the material. This directly pertains to its appearance without altering its composition, so it is a physical property. Additionally, color does not change regardless of the size of the lemon; hence, this is an **intensive** physical property.

Step 2: Analyze Part (b) - Sulfuric acid converts sugar to carbon and steam

The conversion of sugar into carbon and steam when reacting with sulfuric acid involves chemical reactions, altering the composition and identity of the substances involved. Therefore, this is a chemical property. Since it is related to a change in the substance's nature, it cannot be classified as intensive or extensive in the conventional sense of physical properties.

Step 3: Analyze Part (c) - The sample has a mass of 1 kg

Mass measures the amount of matter in a sample, which changes if the amount of the substance changes, thus it is an **extensive** property. As mass does not involve a substance composition or identity alteration, it is a physical property.

Step 4: Analyze Part (d) - Sand is insoluble in water

The inability of sand to dissolve in water describes a physical behavior as it deals with interactions at a physical level without changing sand's composition. Solubility is independent of the amount of sample, making it an **intensive** physical property.

Step 5: Analyze Part (e) - Wood burns in air, forming carbon dioxide and water

Burning results in new substances (carbon dioxide and water) due to chemical reactions, indicating this is a chemical property. Like other chemical properties, it does not categorize as intensive or extensive since these terms apply to physical properties.

Key Concepts

Intensive Properties

Intensive properties are fascinating elements of material science that describe properties independent of the substance's quantity or size. These properties remain consistent regardless of how much or how little of a material you have. For instance, the color of a lemon, such as yellow, is an excellent example of an intensive property. Whether you have a single lemon or a whole basket full, each lemon will still be yellow.
Intensive properties are vital because they help in identifying substances. Besides color, other common examples include:

• Density
• Boiling point
• Melting point

By focusing on these characteristics, scientists can often determine what type of substance they are dealing with, without needing to know the amount of substance in question.

Extensive Properties

Extensive properties are quite the opposite of intensive properties. They depend on the amount of matter present. These types of properties change when the size of the sample changes. A straightforward example is the mass of a sample, like in the case of a 1 kg sample. If you were to divide this sample, the mass of each piece would be less, thus, demonstrating its extensive nature.
Extensive properties are useful when trying to compare quantities or measure the total amount of material. Some key examples include:

• Volume
• Energy
• Total charge

These properties help in calculating the scale of production, resource requirements, and can significantly impact things like cost analysis and material budgets in industrial settings.

Chemical Reactions

Chemical reactions are dynamic processes where substances change into entirely new compounds. These reactions usually involve breaking and forming chemical bonds and result in substances with new chemical identities. A classic example includes how sulfuric acid reacts with sugar, turning it into carbon and steam. This illustrates a profound change at a molecular level.
Chemical reactions are essential to many natural processes and industrial applications. Here are a few critical features:

• Release or absorption of energy
• Formation of new products
• Irreversibility under normal conditions

Chemical reactions are pivotal in understanding matter transformations, energy conversions, and in developing new materials and products, enhancing our ability to manipulate the natural world for various applications.