Question

When a person has a severe fever, one therapy to reduce the fever is an "alcohol rub." Explain how the evaporation of alcohol from the person's skin removes heat energy from the body.

Short answer

During an alcohol rub therapy, a diluted alcohol solution is applied to a person's skin to evaporate quickly. Alcohol has a lower boiling point and absorbs heat energy more effectively than water, making it an efficient cooling agent. As the alcohol evaporates, it absorbs heat energy from the body, causing a rapid decrease in body temperature. This process effectively reduces fever by removing heat energy from the body through the evaporation of alcohol.

Step-by-step solution

Understand the basics of evaporation

Evaporation is a process in which a liquid transforms into a gas. This process requires energy, which is usually provided by heat. As the liquid molecules absorb heat, they gain enough energy to break the bonds holding them together and escape as gas molecules. It's important to note that evaporation is a cooling process, as it removes heat energy from the substance being evaporated.

Recognize the cooling effect of evaporation

The cooling effect from evaporation occurs as the heat energy is absorbed by the liquid to transition to a gaseous state. In turn, this causes the remaining liquid to become cooler. You can feel this effect firsthand by wetting your skin and then blowing on it – as the water evaporates, it absorbs heat from your skin, causing a cooling sensation.

Examine the properties of alcohol

Alcohol has a lower boiling point than water, meaning it evaporates more easily and at lower temperatures. In fact, the boiling point of alcohol is approximately \(78^{\circ}C (172^{\circ}F)\), whereas water boils at \(100^{\circ}C (212^{\circ}F)\). Additionally, alcohol absorbs heat energy more effectively than water, making it an efficient cooling agent.

Understand the alcohol rub therapy

During an alcohol rub therapy, a diluted alcohol solution is applied to a person's skin to evaporate quickly. As the alcohol evaporates, it absorbs heat energy from the body, causing a rapid decrease in body temperature. This is an effective method for lowering body temperature in case of severe fever as it allows a quicker loss of heat than if only water was used.

Summarize the process

To summarize, the evaporation of alcohol from the skin during an alcohol rub therapy works as follows: 1. The alcohol solution is applied to the person's skin. 2. The alcohol absorbs heat energy from the person's body, causing the alcohol molecules to transition from a liquid to a gaseous state. 3. As the energy is absorbed, the body temperature decreases. 4. The alcohol's low boiling point and efficient heat absorption properties contribute to the rapid cooling effect, effectively reducing the fever. By understanding these concepts, we can explain how the evaporation of alcohol from a person's skin during an alcohol rub therapy removes heat energy from the body, reducing fever.