Question
Dip a Q-tip in plain water and swipe it across the table (apply pressure as your swipe). Time how long it takes to completely evaporate
Dip a Q-tip in alcohol and swipe it across the table. Time how long it takes to completely evaporate.
Water
Alcohol
Time to evaporate
145+
18
You should have discovered that the water took longer to evaporate. Why do you think this was the case?
Answers
GPT-4o mini
The observation that water took longer to evaporate compared to alcohol can be explained by several factors related to the physical properties of the two liquids:
1. **Vapor Pressure**: Alcohol generally has a higher vapor pressure than water. This means that alcohol molecules are more inclined to enter the vapor phase compared to water molecules at the same temperature, which contributes to faster evaporation.
2. **Molecular Weight and Structure**: Water (H2O) has a higher molecular weight and a more complex hydrogen bonding network compared to most alcohols (like ethanol, which is C2H5OH). These hydrogen bonds in water are stronger, making it more difficult for water molecules to escape into the vapor phase.
3. **Boiling Points**: The boiling point of water (100°C at standard atmospheric pressure) is higher than that of common alcohols like ethanol (about 78°C). This lower boiling point for alcohol means that it can change from liquid to gas more readily.
4. **Heat of Vaporization**: The heat of vaporization, which is the amount of energy required to convert a unit mass of a liquid into vapor without a change in temperature, is higher for water compared to alcohol. This means that alcohol requires less energy to evaporate compared to water.
These factors combined explain why the alcohol evaporated significantly faster than the water in your experiment.
1. **Vapor Pressure**: Alcohol generally has a higher vapor pressure than water. This means that alcohol molecules are more inclined to enter the vapor phase compared to water molecules at the same temperature, which contributes to faster evaporation.
2. **Molecular Weight and Structure**: Water (H2O) has a higher molecular weight and a more complex hydrogen bonding network compared to most alcohols (like ethanol, which is C2H5OH). These hydrogen bonds in water are stronger, making it more difficult for water molecules to escape into the vapor phase.
3. **Boiling Points**: The boiling point of water (100°C at standard atmospheric pressure) is higher than that of common alcohols like ethanol (about 78°C). This lower boiling point for alcohol means that it can change from liquid to gas more readily.
4. **Heat of Vaporization**: The heat of vaporization, which is the amount of energy required to convert a unit mass of a liquid into vapor without a change in temperature, is higher for water compared to alcohol. This means that alcohol requires less energy to evaporate compared to water.
These factors combined explain why the alcohol evaporated significantly faster than the water in your experiment.