Question

State whether each of the following is a physical or a chemical property: (a) Titanium is ductile. (b) Zinc generates a gas in acid. (c) Yellow phosphorus ignites in air. (d) Chromium conducts heat.

Short answer

(a) Physical property, (b) Chemical property, (c) Chemical property, (d) Physical property.

Step-by-step solution

Understanding Physical Properties

Physical properties describe the characteristics of a substance that can be observed or measured without changing its composition. Examples include color, melting point, boiling point, density, and states of matter.

Understanding Chemical Properties

Chemical properties describe the ability of a substance to undergo specific chemical changes or reactions that transform it into a different substance. Examples include reactivity with other chemicals, flammability, and acidity.

Identify Property of Titanium

Ductility refers to the ability of a material to be drawn into thin wires, a change in form rather than chemical composition. Therefore, ductility is a physical property. Answer for (a) is physical property.

Identify Property of Zinc

When zinc generates a gas in acid, it indicates that a chemical reaction occurs, leading to a change in composition by forming a new substance. Thus, generation of gas in reaction with acid is a chemical property. Answer for (b) is chemical property.

Identify Property of Yellow Phosphorus

When yellow phosphorus ignites in air, it undergoes a combustion reaction, changing composition as it burns. This reactivity is characteristic of a chemical change. Therefore, it is a chemical property. Answer for (c) is chemical property.

Identify Property of Chromium

Conducting heat is a property describing the ability to transfer thermal energy without altering the substance's chemical composition. Thus, heat conduction is a physical property. Answer for (d) is physical property.

Key concepts

Physical Properties

Physical properties are characteristics of materials that can be observed or measured without altering the substance's chemical composition. They are essentially the aspects of a material that you can sense or calculate while keeping the material's identity intact. Some of the most common physical properties include:

• Color: The hue or shade that is seen, like silver for most metals.
• Melting and boiling points: The temperatures at which a substance changes state, such as from solid to liquid or liquid to gas.
• Density: This describes how compact the matter within a substance is, typically measured in units like grams per cubic centimeter.
• State of matter: Whether a substance exists as a solid, liquid, or gas at a given temperature and pressure.
• Conductivity: The ability to transfer heat or electricity, like chromium's capability to conduct heat.
• Ductility: As seen with titanium, this property refers to the ability to be stretched into a wire without breaking, highlighting its flexibility in physical form.

These properties can be crucial for identifying and using materials in various applications without engaging in chemical reactions.

Chemical Properties

Chemical properties detail a material's potential to undergo a transformation that changes its chemical composition. This type of property is observed when substances react with each other, resulting in completely new chemical entities. Understanding chemical properties helps in predicting the behavior of substances in various chemical reactions. Examples include:

• Reactivity: This shows how a substance interacts with other chemicals. For instance, zinc reacts with acid to produce gas, indicating a chemical change.
• Flammability: The capacity of a substance to ignite and burn in the presence of oxygen, as exhibited by yellow phosphorus igniting in the air.
• Acidity or basicity: The tendency of a substance to act as an acid or a base in solution.
• Oxidation states: These can influence how a substance reacts with oxygen or other oxidizing agents, resulting in a new compound.

Chemical properties are like the personality traits of a material's reactivity, predicting how it might change when mixed with other substances.

Properties of Materials

When we talk about the properties of materials, we consider both physical and chemical properties to provide a complete picture of how materials behave in different conditions and uses. These properties define how a material appears, reacts, and can be utilized in practical applications. Consider each property type: **Physical Properties:**

• They allow us to understand the usability, shape, and texture of materials without altering their nature.
• They include critical factors like melting points, density, and the ability to conduct electricity.

**Chemical Properties:**

• Involve how materials interact and change on a molecular level, such as reactivity with acids or combustibility.
• Help predict how a material can be transformed into other substances, leading to new material synthesis.

When selecting materials for specific jobs, knowing both physical and chemical properties helps us choose the right materials, whether for constructing buildings, manufacturing electronics, or even in biological applications. Understanding these properties allows us to tailor materials to desired requirements, improving efficiency, safety, and performance in practical uses.