Question

A cotton ball dipped in alcohol is wiped across a tabletop. Would the resulting smell of the alcohol be more or less noticeable if the tabletop were much warmer? Explain.

Short answer

A warmer tabletop makes the alcohol smell more noticeable due to increased evaporation.

Step-by-step solution

Understand the Process

When you wipe a tabletop with a cotton ball dipped in alcohol, the alcohol begins to evaporate. Evaporation is the process of a liquid turning into a gas and dispersing into the air, which carries the alcohol molecules with it, leading to the smell.

Impact of Temperature on Evaporation

Temperature affects how quickly a liquid evaporates. Specifically, higher temperatures increase the kinetic energy of the molecules, causing them to evaporate more rapidly.

Apply Temperature to the Situation

If the tabletop is much warmer, the increased energy from the heat helps the alcohol molecules escape into the air quicker, heightening the evaporation rate and thus the concentration of alcohol vapor in the air.

Determine the Effect on Smell

Because more alcohol evaporates in a shorter period of time when the tabletop is warm, there would be a greater concentration of alcohol vapor in the air near the table, making the smell more noticeable.

Key concepts

Temperature Effects on Evaporation

When you consider evaporation, temperature plays a crucial role. Imagine a warm day at the beach: water puddles dry up faster under the sun. This is because heat, a form of energy, boosts the activity of water molecules. The same principle applies when alcohol on a tabletop evaporates, especially if the table is warm.
The temperature of the table directly affects how quickly alcohol evaporates. Higher temperatures mean more heat energy is transferred to the alcohol molecules. This energy transforms into kinetic energy, exciting the molecules and making them ready to escape into the air.
A warmer table means faster evaporation, which leads to a more intense and rapid dispersal of alcohol vapors. The warmth accelerates the process, ensuring that the smell is both stronger and more immediate than it would be at cooler temperatures. By knowing this, you can predict how temperature changes impact evaporation in everyday situations.

Kinetic Energy and Molecular Movement

At the heart of evaporation lies kinetic energy, the energy of motion. Every molecule of a substance, like alcohol, has kinetic energy as it moves. This energy is crucial for the phase transition from liquid to gas.
As temperature increases, so does the kinetic energy. The rise in kinetic energy causes alcohol molecules to vibrate and move more swiftly. With enough energy, they can break free from the liquid state. This movement out of the liquid and into the air is what we perceive as evaporation.
The more kinetic energy the molecules have, the quicker they escape. Therefore, in warmer conditions, the chances of molecules crossing the liquid-gas boundary increases. This underpins why higher temperatures result in faster and more noticeable evaporation.

Effects of Vapor Concentration on Smell

When alcohol evaporates, it forms vapor, or gas molecules suspended in the air. The concentration of these molecules significantly affects how strong a smell you perceive.
Vapor concentration depends on how many molecules are present in a certain amount of air. In a warm environment, evaporation intensifies, leading to more alcohol molecules escaping into the air. This results in a higher concentration of vapor near the surface where evaporation occurs.
For the smell to become noticeable, the vapor concentration must reach a certain level. Higher concentrations mean more molecules stimulate your sense of smell, making the scent of alcohol more pronounced. Therefore, the warmth of the table significantly increases the likelihood that the alcohol smell will quickly become apparent to anyone nearby.