# Surface tension of water+alcohol

• toni_2374
In summary, the solubility of alcohols in water affects the surface tension of the mixture, with higher solubility resulting in a greater decrease in surface tension. This can be explained by the Langmuir equation, which relates surface tension to surface concentration.
toni_2374

## Homework Statement

explain the change in surface tension of mixture of water+alcohol(n-octanol,n-heptanol,n-butanol)? discuss their degree of their solubility in water and this affect to surface tension?

## Homework Equations

L=SURFACE CONCENTRATION
δ=SURFACE TENSSION
C=CONCENTRATION OF ALCOHOL IN WATER
L=(1/RT)*∂δ/∂ln(c)

## The Attempt at a Solution

If a alcohol is soluble a little in water it can change surface tension so much if a little amount of alcohol is added.

As alcohols are more soluble in water, the surface tension decreases. This is because the alcohol molecules form a monolayer on the surface of the liquid and the molecules of water are displaced by the alcohol molecules. The decrease in surface tension is due to the lower surface concentration of water molecules and the higher surface concentration of alcohol molecules. To explain the change in surface tension of mixture of water and alcohol, it can be expressed in terms of the Langmuir equation, which states that the surface tension (δ) is dependent on the surface concentration (L) as follows: δ = RTL / (1 + C/L) where R is the gas constant, T is the temperature and C is the concentration of alcohol in the water. The degree of solubility of an alcohol affects the surface concentration of the molecules at the surface of the liquid. As the solubility of an alcohol increases, the surface concentration of the molecules also increases, resulting in a decrease in surface tension. For example, n-butanol has a higher solubility in water compared to n-octanol and n-heptanol, so when n-butanol is added to water, the surface tension will decrease more than when n-octanol or n-heptanol are added.

## 1. What is surface tension?

Surface tension is a physical property of liquids that describes the force that causes the surface of a liquid to behave like a thin, elastic film. This force is created by the cohesive interactions between the molecules of the liquid.

## 2. How does the addition of alcohol affect the surface tension of water?

Alcohol molecules are smaller and have weaker cohesive forces compared to water molecules. When added to water, they disrupt the cohesive interactions between water molecules, resulting in a decrease in surface tension. This is because the alcohol molecules are more easily pulled away from the surface, causing less resistance to external forces.

## 3. What is the relationship between surface tension and concentration of alcohol in water?

The surface tension of water decreases as the concentration of alcohol increases. This is because more alcohol molecules are present to disrupt the cohesive interactions between water molecules, resulting in a weaker surface tension.

## 4. Can the surface tension of water+alcohol be measured?

Yes, the surface tension of a liquid can be measured using a variety of methods such as the drop weight method, capillary rise method, or the du Nouy ring method. These methods involve measuring the force required to pull a needle or ring off the surface of the liquid, which is directly related to the surface tension.

## 5. What practical applications does the study of surface tension of water+alcohol have?

Understanding the surface tension of water+alcohol has various practical applications in industries such as pharmaceuticals, cosmetics, and cleaning products. It also plays a crucial role in processes such as emulsification, foaming, and wetting. Additionally, the study of surface tension can help in understanding the behavior of fluids in various natural phenomena, such as raindrop formation and plant water transport.

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