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The Fickleness of Alcohol: Why Does Mixing Liquids of Different Alcohol Concentrations Change Volume?
Alcoholic beverages are a must at every bar or house party. However, many people have probably never really thought about this: Why does the volume of alcohol change when you mix different concentrations of alcohol together? There are interesting chemical principles and biological foundations behind this phenomenon, which we will explore in depth below.
Alcohol concentration and volume changes
Alcohol is measured as a percentage by volume, often labeled "alcohol by volume" (ABV). This means how many milliliters of pure alcohol are in 100 milliliters of solution. When different concentrations of alcohol are mixed, the volume changes observed cannot be explained by simple addition. This phenomenon is called "partial molar volume" by chemists.
When water and alcohol (such as ethanol) are mixed, the interaction between the molecules causes the volume of the mixture to change.
The combination of water and alcohol: interaction between molecules
Both water and ethanol are polar solvents, which means they are capable of forming hydrogen bonds. When water is added to ethanol, the water molecules are attracted to the hydroxyl groups of the ethanol and change the polar environment of each other. This attraction allows for a closer packing between the water and alcohol molecules, causing the total volume of the mixture to become less than desired.
Experimental observation of volume changes
Experiments have shown that when mixing alcohol and water at a concentration below 24%, the volume increases slightly, while mixing above this concentration results in a decrease in volume. This is because at high concentrations, the repulsive force between molecules weakens, leading to the formation of a more compact structure, resulting in a smaller overall volume.
When mixing alcohols of different concentrations, the intuitive feeling that is often difficult to verify is that the total volume of the substance is not equal to the sum of the volumes of its parts.
Regulations and alcohol content standards
Different countries have clear regulations on alcohol content standards. For example, the standard for low-alcohol beer in some countries is 0.5% ABV, while most commercially available non-alcoholic beers are only around 0.05%. These standards not only affect the name of the wine, but also indirectly affect the choice of consumers.
Biological effects of alcohol
Generally healthy people cannot become intoxicated simply by drinking low-alcohol drinks. This is because low concentrations of alcohol have minimal effects on metabolism, and the body's main excretion rate is more likely to cause water intoxication than alcohol intoxication when a large amount of water is taken in.
Summary and reflection
Overall, mixing alcohol and water produces a change in volume due to subtle changes in molecular structure and chemical reactions. This also makes us think, when many people choose alcoholic beverages nowadays, how many of them understand the scientific principles behind these drinks? How will these principles impact our drinking culture and choices?
Have you ever thought about these scientific principles while drinking alcohol?
