Question

Does each statement represent a physical property or a chemical property? a) A pile of leaves slowly rots in the backyard. b) In the presence of oxygen, hydrogen can interact to make water. c) Gold can be stretched into very thin wires.

Short answer

a) Chemical, b) Chemical, c) Physical

Step-by-step solution

Understanding Physical vs. Chemical Properties

Physical properties are characteristics of a substance that can be observed without changing its chemical composition, such as color, density, and state (solid, liquid, gas). Chemical properties describe a substance's potential to undergo some chemical change or reaction by virtue of its composition.

Analyze Statement a

The statement "A pile of leaves slowly rots in the backyard" describes a decomposition process, which is a chemical change as it involves the breakdown of substances into different compounds. Therefore, this statement represents a chemical property.

Analyze Statement b

The statement "In the presence of oxygen, hydrogen can interact to make water" describes a chemical change, as the composition of hydrogen and oxygen changes to form water. Therefore, this statement represents a chemical property.

Analyze Statement c

The statement "Gold can be stretched into very thin wires" describes the ability of gold to deform under tensile stress, known as ductility. This is a physical property because gold's chemical composition does not change in this process.

Key concepts

Chemical Change

A chemical change refers to a process where substances transform into one or more different substances. This involves a change in the chemical composition, making it irreversible by simple physical means. For example, when a pile of leaves rots, it undergoes a chemical change. The organic matter breaks down, forming new substances like carbon dioxide and water. In this context, new compounds are formed, and the original leaves can't be recovered.

Characteristics of chemical changes:

• Formation of new substances
• Irreversibility (without another chemical change)
• Often involves energy change (heat, light)
• May produce gases, odors, or color changes

This concept is essential for understanding various natural processes and synthetic reactions in chemistry.

Physical Change

Physical changes are processes where the form of matter changes but not its chemical identity. These changes are often reversible and do not result in new substances being produced. A classic example of a physical change is the melting of ice into water; the chemical structures of water remain unchanged as H₂O.

Characteristics of physical changes:

• No new substances are formed
• Usually reversible
• No change in chemical properties
• Changes in physical state like melting, freezing, or evaporating are included

Recognizing physical changes can help in understanding the energy and states of matter involved, without the complexity of chemical transformations.

Decomposition Process

Decomposition is a specific type of chemical change where compounds break down into simpler forms or elements. This is usually triggered by heat, light, or microbial activity. A common example is the rotting of organic matter like leaves, where complex organic molecules decompose into basic elements and compounds.

Decomposition plays a crucial role in:

• Nutrient cycling in ecosystems
• Waste management through biodegradation
• Various industrial processes such as extracting metals

This process is not just limited to natural occurrences but also forms part of many synthetic industrial applications, contributing to materials recycling and environment sustainability.

Ductility

Ductility is a physical property that refers to a material's ability to withstand tensile stress and be stretched into a wire. This property is significant in materials like gold and metals, which can be deformed without breaking. For instance, gold is renowned for its ductility, allowing it to be fashioned into thin wires for electrical or decorative purposes.

Key aspects of ductility include:

• Ability to mold into shapes without breaking
• Importance in manufacturing and construction industries
• Indicator of a material's toughness and flexibility

Understanding ductility helps in selecting materials for applications requiring both strength and pliability, like in creating fine jewelry or intricate metalwork.