Problem 96 - Chemistry Matter and Change

Question

Identify each property as chemical or physical. (Chapter 3) a. The element mercury has a high density. b. Solid carbon dioxide sublimes at room temperature. c. Zinc oxidizes when exposed to air. d. Sucrose is a white crystalline solid.

Step-by-Step Solution

Answer

a. Physical, b. Physical, c. Chemical, d. Physical.

Step 1: Identifying Mercury's Density Property

Determine if high density is a chemical or physical property. Density does not involve a change in composition or the production of new compounds, as it is an observable characteristic of matter that relates to mass and volume. Thus, the density of mercury is a physical property.

Step 2: Identifying Sublimation Property of Solid Carbon Dioxide

Consider whether sublimation involves a chemical or physical change. Sublimation is the process where a solid changes to a gas without passing through a liquid phase. This transformation involves a change of state without altering chemical composition, marking it as a physical property.

Step 3: Identifying the Oxidation Property of Zinc

Evaluate whether oxidation involves a chemical or physical change. When zinc oxidizes, it reacts with oxygen in the air to form zinc oxide, indicating a new substance is produced. This is a chemical property, as it describes the ability of a substance to undergo a specific chemical change.

Step 4: Identifying Sucrose's Physical Appearance Property

Assess whether being white and crystalline is a chemical or physical property. The color and crystalline structure of sucrose pertain to its appearance and form without changing chemical composition, making them physical properties.

Key Concepts

Chemical Properties

Chemical properties are characteristics of a material that reveal how it reacts or changes into a new substance. These properties are often observed during a chemical reaction or transformation. For example, when zinc oxidizes upon exposure to air, this showcases zinc's chemical property to react with oxygen, producing zinc oxide, a new compound.

Some key aspects of chemical properties include:

• Reactivity with other chemicals
• Toxicity
• Flammability
• Heat of combustion

In any scenario where a change in the molecular structure or composition occurs, you're observing a chemical property.

Physical Properties

Physical properties can be observed or measured without changing the substance's chemical structure. These include features like color, odor, melting point, boiling point, density, and phase of matter.

For example, the high density of mercury is a physical property because it can be measured without altering mercury's composition. Similarly, the white crystalline appearance of sucrose pertains to its form and texture and does not involve any chemical change.

Key physical properties include:

• Color
• State (solid, liquid, gas)
• Solubility
• Magnetic properties

These properties are crucial in identifying substances and predicting their behavior in different conditions.

Sublimation

Sublimation is a fascinating physical process where a solid turns directly into a gas, bypassing the liquid phase entirely. This phenomenon occurs in substances like dry ice (solid carbon dioxide) at room temperature.

Sublimation involves merely a change in state while keeping the chemical identity intact, thus it is categorized as a physical property.

Some basic examples and practical applications of sublimation include:

• Dry ice used in fog machines
• Freeze-drying foods
• Purifying substances in the lab

Understanding sublimation helps in understanding phase changes and the energy dynamics involved in the process.

Oxidation

Oxidation is a chemical process where a substance combines with oxygen to form oxides. It is often associated with the loss of electrons from a molecule, atom, or ion. An everyday example of oxidation is the rusting of iron.

When zinc is exposed to oxygen in the air, it undergoes oxidation, forming zinc oxide, showcasing its chemical property. This process is crucial in various industrial applications and natural processes.

Some examples of oxidation include:

• Formation of rust (iron oxide)
• Burning of hydrocarbons
• Respiration in living organisms

Oxidation can also be part of larger reaction types, such as redox reactions, which play a key role in energy transfer and chemical synthesis.

Density

Density is a fundamental physical property defined as mass per unit volume, typically expressed in units such as grams per cubic centimeter (g/cm³). It describes how much matter is packed into a given space.

For instance, mercury's high density indicates its compact matter concentration, which can be measured without changing its chemical identity, thus marking it a physical property.

Important aspects of density include:

• Identifying substances
• Determining buoyancy
• Separation processes

Density plays a significant role in science and engineering, helping to predict the behavior of materials and substances under different scenarios.