Question

Give two examples of (a) a volatile liquid and (b) a nonvolatile liquid.

Short answer

Volatile: Acetone, Ethanol. Nonvolatile: Glycerol, Mineral oil.

Step-by-step solution

Define Volatile and Nonvolatile Liquids

A volatile liquid is one that evaporates readily at room temperature because it has a high vapor pressure. Examples of volatile liquids include acetone and ethanol. A nonvolatile liquid, on the other hand, does not evaporate easily under normal conditions due to its low vapor pressure. Examples of nonvolatile liquids include glycerol and mineral oil.

Example of Volatile Liquids

Volatile liquids tend to have low boiling points and evaporate quickly. Two typical examples are: - **Acetone**: Commonly used as a solvent in nail polish remover. - **Ethanol**: Found in alcoholic beverages; it evaporates easily at room temperature.

Example of Nonvolatile Liquids

Nonvolatile liquids evaporate slowly and have higher boiling points. Two examples are: - **Glycerol**: A thick, syrupy liquid used in cosmetics and pharmaceuticals. - **Mineral Oil**: A clear, colorless oil used as a lubricant and moisturizer.

Key concepts

Vapor Pressure

Vapor pressure is an essential concept when discussing volatile and nonvolatile liquids. It refers to the pressure exerted by a vapor in equilibrium with its liquid phase at a given temperature. In simpler terms, it is the tendency of a liquid's molecules to escape into the gaseous phase.
When a liquid has a high vapor pressure, it means that many of its molecules are transitioning from the liquid phase to the vapor phase. This usually occurs because the molecules of the liquid have enough energy to break free from the surface. Volatile liquids, like acetone and ethanol, have high vapor pressures at room temperature, which is why they evaporate readily.
On the other hand, nonvolatile liquids such as glycerol and mineral oil have low vapor pressures. Their molecules don't have enough energy to easily escape into the vapor phase under normal conditions. Consequently, these liquids don't evaporate as quickly. Understanding vapor pressure helps in predicting how fast a liquid can evaporate in given conditions.

Evaporation

Evaporation is the process where molecules at the surface of a liquid gain enough energy to become gas. This often occurs at a temperature below the boiling point of the liquid.
Several factors affect the rate of evaporation:

• Temperature: Higher temperatures give molecules more energy, allowing them to escape more easily.
• Surface Area: More surface area means there are more molecules available to escape, increasing evaporation.
• Pressure: Lower atmospheric pressure reduces the energy needed for molecules to evaporate.

Liquids like acetone and ethanol have molecules that can escape quickly, making them volatile. They evaporate faster compared to nonvolatile substances such as glycerol and mineral oil. When choosing solvents or other materials for uses that involve evaporation, understanding this property can be quite crucial.

Boiling Point

The boiling point is the temperature at which a liquid's vapor pressure equals atmospheric pressure, causing the liquid to transition into a gas rapidly. At this point, bubbles form within the liquid.
1. **Volatile Liquids:** These typically have lower boiling points due to their high vapor pressure. Acetone, for example, boils at about 56°C (132.8°F), and ethanol boils at around 78°C (172.4°F). Their lower boiling points allow them to change into gas more quickly and with less heat. 2. **Nonvolatile Liquids:** These have higher boiling points because their vapor pressure is lower compared to the atmospheric pressure at lower temperatures. As such, they're more heat-resistant and require more energy to boil. For example, glycerol has a boiling point of about 290°C (554°F). Knowing the boiling point of a substance is vital in applications where temperature control is important, such as cooking, chemical reactions, and manufacturing processes. Understanding these differences helps us make informed choices about which liquids to use based on their properties.