Question

State whether each of the following is a physical or a chemical property of gold: (a) yellow color (b) high density (c) conducts electricity (d) reacts with nitric acid

Short answer

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

Step-by-step solution

Understanding Properties

A physical property can be observed or measured without changing the substance's identity, while a chemical property describes a substance's ability to undergo chemical changes.

Analyzing Yellow Color

Gold's yellow color is a characteristic that can be observed directly and does not involve a chemical change. Therefore, yellow color is a physical property.

Analyzing High Density

Density is a measure of mass per unit volume and can be determined without altering the substance itself. Gold's high density is a physical property.

Analyzing Conducts Electricity

The ability of gold to conduct electricity relates to the movement of electrons within the metal without changing its chemical structure. Hence, conducting electricity is a physical property of gold.

Analyzing Reacts with Nitric Acid

A reaction with nitric acid indicates a change in the chemical composition of gold, which is characteristic of a chemical property.

Key concepts

Physical Properties

Physical properties are characteristics that can be observed or measured without altering the substance's chemical nature. These properties provide insight into a material's aesthetic or functional aspects, but not how it reacts chemically.

Physical properties include:

• Color
• Mass
• Volume
• Density
• Melting and boiling points
• Conductivity

For instance, noting the yellow color, high density, and electrical conductivity of gold involves observing physical properties. These aspects do not require changing the substance into a different chemical form, and thus, they reveal a lot about the metal in its natural state.

Gold

Gold is a precious, naturally occurring metal known for its attractive yellow color and significant role in commerce and investment. Beyond its aesthetic appeal, gold also boasts several intrinsic properties that make it highly valuable in various applications.

Some key attributes of gold include:

• High Density: Gold is renowned for its weight and density, making it notably heavier than other metals per unit of volume.
• Electrical Conductivity: Though not the highest of all metals, gold's ability to conduct electricity without tarnishing is critical, especially in electronics.
• Resistance to Tarnish and Corrosion: Gold doesn't rust or corrode easily, maintaining its lustrous appearance over time.

Additionally, gold's softness and malleability allow it to be fashioned into various shapes and designs. Despite these physical properties, its chemical properties, such as reaction to certain acids, have vital roles in understanding its broader industrial uses.

Physical vs Chemical Changes

Understanding the difference between physical and chemical changes is crucial in chemistry. A physical change in a substance doesn't alter its chemical composition, merely affecting its state or form. In contrast, a chemical change results in one or more new substances.

Features of physical changes include:

• No new substance formation
• Reversibility
• Changes in state or appearance

For example, melting gold is a physical change; it turns from solid to liquid but remains chemically the same.

On the other hand, chemical changes involve:

• The formation of new substances
• Transfer of energy, like heat or light
• Irreversibility

When gold reacts with nitric acid, it undergoes a chemical change, as the reaction alters its chemical structure. Recognizing these differences helps in predicting and identifying changes in materials during chemical processes.