Which Of The Following Is Not A Physical Property

Which of the Following is NOT a Physical Property? A Deep Dive into Physical and Chemical Properties

Understanding the difference between physical and chemical properties is fundamental in chemistry and many related scientific fields. While seemingly simple, the distinction can be nuanced, particularly when dealing with complex substances or reactions. This article will delve into the core concepts of physical and chemical properties, providing clear examples to help you confidently distinguish between them. We'll then explore several scenarios, identifying which properties are not physical, emphasizing the underlying principles behind each classification.

What are Physical Properties?

Physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical composition. These properties describe the substance's appearance, texture, and behavior without altering its fundamental molecular structure. Examples of physical properties include:

Observable Physical Properties:

• Color: The visual appearance of a substance (e.g., red, blue, green).
• Odor: The smell emitted by a substance (e.g., sweet, pungent, odorless).
• Texture: The feel of a substance (e.g., rough, smooth, silky).
• Shape: The physical form of a substance (e.g., cubic, spherical, amorphous).
• State of Matter: Whether the substance exists as a solid, liquid, or gas.
• Density: The mass per unit volume of a substance (e.g., g/cm³).
• Melting Point: The temperature at which a solid turns into a liquid.
• Boiling Point: The temperature at which a liquid turns into a gas.
• Solubility: The ability of a substance to dissolve in a solvent.
• Hardness: A measure of a solid's resistance to scratching or indentation.
• Malleability: The ability of a substance to be hammered into thin sheets.
• Ductility: The ability of a substance to be drawn into wires.
• Viscosity: The resistance of a fluid to flow.
• Conductivity: The ability of a substance to conduct electricity or heat.
• Luster: The way a substance reflects light (e.g., shiny, dull).
• Brittleness: The tendency of a solid material to break easily upon impact.

Measurable Physical Properties:

Many physical properties can be quantitatively measured, providing numerical data for analysis and comparison. These measurements are crucial in scientific experimentation and material characterization.

What are Chemical Properties?

Chemical properties describe a substance's ability to undergo chemical changes or reactions. Observing chemical properties requires a chemical reaction, resulting in the formation of new substances with different chemical compositions. Key indicators of chemical changes include:

• Formation of a gas: Often observed as bubbles or effervescence.
• Change in color: A significant shift in the substance's visual appearance.
• Formation of a precipitate: The formation of a solid from a solution.
• Change in temperature: A noticeable increase or decrease in temperature.
• Light or sound emission: The release of light or sound energy.
• Irreversible changes: The changes are difficult or impossible to reverse without further chemical reactions.

Examples of chemical properties include:

• Flammability: The ability of a substance to burn in the presence of oxygen.
• Reactivity with acids or bases: The substance's behavior when exposed to acids or bases.
• Toxicity: The potential of a substance to cause harm to living organisms.
• Stability: The substance's resistance to decomposition or chemical change.
• Corrosion resistance: A substance's ability to resist chemical degradation.
• Oxidizing ability: The substance's ability to oxidize other substances.
• Reducing ability: The substance's ability to reduce other substances.

Distinguishing Between Physical and Chemical Changes

It's crucial to understand that physical changes alter the form or appearance of a substance without changing its chemical composition, while chemical changes alter the chemical composition of a substance, forming new substances.

Physical Change Examples:

• Melting ice (water changes from solid to liquid)
• Crushing a can (altering the shape of the aluminum)
• Dissolving sugar in water (sugar molecules distribute in water but remain sugar molecules)
• Boiling water (water changes from liquid to gas)

Chemical Change Examples:

• Burning wood (wood reacts with oxygen, forming ash and gases)
• Rusting iron (iron reacts with oxygen and water, forming iron oxide)
• Baking a cake (ingredients undergo chemical reactions, forming a new substance)
• Digesting food (food undergoes chemical breakdown in the body)

Identifying Non-Physical Properties in Scenarios

Let's analyze several scenarios to pinpoint which properties are not physical properties, focusing on the reasons behind our classifications.

Scenario 1: Which of the following is NOT a physical property?

• A) Density
• B) Flammability
• C) Boiling point
• D) Color

Answer: B) Flammability

Explanation: Density, boiling point, and color are all directly observable or measurable without altering the chemical composition of the substance. Flammability, however, describes the substance's ability to undergo a combustion reaction, a chemical change. This process alters the chemical composition of the substance, forming new products (e.g., carbon dioxide and water).

Scenario 2: Which of the following is NOT a physical property?

• A) Malleability
• B) Reactivity with water
• C) Melting point
• D) Solubility

Answer: B) Reactivity with water

Explanation: Malleability, melting point, and solubility are all physical properties. They can be observed or measured without altering the chemical identity of the substance. Reactivity with water, on the other hand, describes a chemical reaction where the substance interacts with water, potentially forming new compounds.

Scenario 3: A student observes several properties of a metal sample. Which observation describes a chemical property?

• A) The metal is shiny.
• B) The metal is easily shaped.
• C) The metal reacts vigorously with acid.
• D) The metal has a high density.

Answer: C) The metal reacts vigorously with acid.

Explanation: Shininess, malleability (easily shaped), and density are all physical properties. The vigorous reaction with acid indicates a chemical change, transforming the metal into new chemical compounds.

Scenario 4: Which of the following properties is NOT a physical property of a liquid?

• A) Viscosity
• B) Boiling point
• C) pH
• D) Density

Answer: C) pH

Explanation: Viscosity, boiling point, and density are all physical properties describing the liquid's behavior or characteristics. pH, however, measures the concentration of hydrogen ions (H⁺) in a solution, which reflects the chemical composition and acidity/basicity of the liquid. Determining pH requires a chemical measurement and involves the liquid's interactions with other substances.

Scenario 5: Consider the process of burning a candle. Which of the following is a chemical property involved in this process?

• A) The color of the candle wax.
• B) The melting point of the candle wax.
• C) The flammability of the candle wax.
• D) The hardness of the candle wax.

Answer: C) The flammability of the candle wax.

Explanation: The color, melting point, and hardness are all physical properties of the candle wax. Flammability, however, is a chemical property because it describes the wax's ability to undergo combustion, a chemical reaction with oxygen that produces new substances (carbon dioxide, water, and other byproducts).

Conclusion

The distinction between physical and chemical properties is crucial for understanding the nature of matter and its transformations. By carefully considering whether a property can be observed or measured without altering the chemical composition of a substance, you can confidently identify which properties are physical and which are chemical. Remember to focus on the underlying chemical changes involved and look for indicators like gas formation, color changes, temperature changes, and the formation of precipitates. Mastering this distinction is fundamental to successful study in chemistry and many related scientific fields. Through consistent practice and critical analysis of various scenarios, you will develop a strong understanding of these essential concepts.