Question

Classify each property as physical or chemical. (a) the tendency of silver to tarnish (b) the shine of chrome (c) the color of gold (d) the flammability of propane gas

Short answer

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

Step-by-step solution

Understanding Physical and Chemical Properties

Physical properties can be observed or measured without changing the composition of matter. Physical properties include appearance, texture, color, odor, melting point, boiling point, density, and solubility. Chemical properties include reactivity with other chemicals, toxicity, flammability, and acidity or basicity. To classify each given property, decide whether the property describes a substance's inherent characteristic without altering its composition (physical) or whether the property describes its reactiveness or changes it undergoes (chemical).

Classifying the Tendency of Silver to Tarnish

Tarnishing of silver occurs when silver reacts with sulfur compounds present in the air, forming silver sulfide, which is a chemical change. Thus, the tendency of silver to tarnish is a chemical property.

Classifying the Shine of Chrome

The shine of chrome is the result of chrome's ability to reflect light, which can be observed without altering the substance itself. Therefore, the shine of chrome is a physical property.

Classifying the Color of Gold

The color of gold is an observed feature that does not require a chemical reaction or alter the gold itself. Hence, the color of gold is a physical property.

Classifying the Flammability of Propane Gas

Flammability is a substance's ability to burn in the presence of oxygen, which is a chemical reaction resulting in new substances. Therefore, the flammability of propane gas is a chemical property.

Key concepts

Classification of Matter

Understanding the classification of matter is crucial in the field of chemistry. It involves grouping substances based on their physical and chemical properties. Matter can be classified into pure substances, which include elements and compounds, and mixtures, which combine different substances without chemical bonds. Pure substances have a fixed composition and exhibit specific properties, while mixtures can be separated into their components through physical means such as filtration or distillation.

For example, in the classification exercise, silver, chrome, and gold are elements, which are pure substances, whereas propane gas is a compound consisting of carbon and hydrogen atoms. Recognizing whether a property is physical or chemical is part of how we differentiate between these types of matter and understand their behaviors in various environments.

Chemical Reactivity

The concept of chemical reactivity refers to the tendency of a substance to engage in chemical reactions with other substances. This intrinsic quality determines how a substance will interact with others to form new products. Factors like electron configurations, the presence of unpaired electrons, and the potential of atoms to achieve a stable configuration often dictate a substance's reactivity.

In the context of the exercise, tarnishing of silver is a result of chemical reactivity. Silver reacts with sulfur compounds in the air, a process indicating that silver is chemically reactive towards sulfur. Understanding reactivity is vital for predicting and explaining how substances will behave during chemical interactions.

Physical Characteristics

The physical characteristics of a substance are the attributes that can be measured or observed without altering the substance's chemical composition. These include texture, color, melting point, boiling point, density, and the ability to conduct electricity or transfer heat. Physical properties are used extensively in identifying and classifying substances.

In our exercise, the shine of chrome and the color of gold are considered physical characteristics. These attributes do not change the substances' identities and are evident through simple observation. When students grasp the significance of physical properties, they can more adeptly categorize and differentiate materials in a non-destructive way.

Flammability

Among chemical properties, flammability is a particularly important one as it pertains to the ability of a substance to ignite and burn when introduced to an oxidizer, such as oxygen. Flammability is directly related to chemical reactivity since it involves the reaction of a substance with oxygen to release energy in the form of light and heat.

Propane gas's flammability, which was addressed in the exercise, makes it an excellent subject for studying chemical kinetics, reaction mechanisms, and energy transformations, as well as for understanding the risks associated with combustible materials. Teaching students to recognize flammability as a chemical property enhances their comprehension of safety and practical applications in chemistry.