Question

State whether each of the following is a physical or a chemical property: (a) Ether is flammable. (b) Bromine is a reddish-orange liquid. (c) Ethanol vaporizes at \(78^{\circ} \mathrm{C}\). (d) Steam condenses to water at \(100^{\circ} \mathrm{C}\)

Short answer

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

Step-by-step solution

Understanding Physical and Chemical Properties

A physical property of a substance is one that can be observed or measured without changing the substance's identity. Examples include color, boiling point, and melting point. A chemical property involves a substance's ability to undergo changes that transform it into different substances, such as flammability and reactivity.

Identifying the Property of Ether

Ether is described as flammable. Flammability is a chemical property because it involves the substance's ability to react with oxygen to combust, changing its chemical identity.

Identifying the Property of Bromine

Bromine is described as a reddish-orange liquid. This description pertains to its color, which can be observed without altering the substance. Therefore, this is a physical property.

Identifying the Property of Ethanol

Ethanol vaporizes at \(78^{\circ} C\). Vaporization is a change from liquid to gas, which is a physical change, as it does not change the chemical structure of ethanol. Hence, vaporization is a physical property.

Identifying the Property of Steam Condensing

Steam condenses to water at \(100^{\circ} C\). Condensation is a phase change from gas to liquid, maintaining the substance's identity as the same chemical (H₂O). Thus, this is a physical property.

Key concepts

Physical Properties

Physical properties are characteristics of a substance that can be observed or measured without altering the substance's chemical structure. This means that when you observe a physical property, the substance itself remains the same. The composition doesn't change during physical processes. Some examples of physical properties include:

• Color: The appearance of a substance, like bromine's reddish-orange hue, can be recognized without changing its structure.
• Boiling Point: The temperature at which a substance changes from liquid to gas - such as ethanol, which vaporizes at \(78^{\circ} \mathrm{C}\).
• Melting Point: The temperature at which a substance changes from solid to liquid.
• Density, Texture, and Mass: These are other examples of physical properties.

Observing these properties does not involve any change in the substance’s fundamental structure. This makes them an important aspect in identifying substances and understanding how they will behave under different physical conditions.
For instance, steam condensing to water at \(100^{\circ} \mathrm{C}\) is a physical change since the chemical identity of water remains the same.

Chemical Properties

Chemical properties describe a substance's potential to undergo specific chemical changes. These properties can only be observed when a substance is transforming into another substance, meaning that the chemical identity alters. This often results in new products and an energy exchange. Key aspects of chemical properties include:

• Reactivity: How readily a substance interacts with other substances.
• Flammability: As seen with ether, its ability to ignite and burn in the presence of oxygen is a chemical property.
• Acidity/Baseness: The tendency to either donate or accept protons.
• Corrosiveness: The ability to erode or wear away materials.

Understanding these properties is essential for predicting how substances will react in different environments and applications. Observing chemical properties typically entails a chemical change where bonds are broken, and new ones are formed.

Flammability

Flammability is a chemical property that defines how easily a substance can catch fire in the presence of oxygen. When a substance burns, it undergoes combustion, a chemical reaction that usually produces heat and light. In this reaction, new substances are formed, distinguishing it as a chemical process.
For example:

• Ether: This substance is noted for being extremely flammable. Its molecules react with oxygen in the air to produce carbon dioxide, water, and other byproducts, altering its original composition.
• General Implications: Flammable substances must be handled carefully, respecting safety protocols to prevent unwanted ignition.

Understanding flammability is crucial in fields like chemistry and engineering, where safe handling and storage of combustibles are of utmost importance. Recognizing the flammability of substances can help prevent accidents and ensure that materials are used in contexts where they are safe and stable.