explain why the surface tension of water is greater than that of methylated spirit
The difference in surface tension between water and methylated spirit can be attributed to the intermolecular forces at play within each substance.
Surface tension is a measure of the cohesive forces between molecules in a liquid that creates a "skin" or elastic-like film on its surface. It is caused by the imbalance of attractive forces between the molecules at the surface when compared to the ones in the bulk of the liquid.
In the case of water, the strong intermolecular forces known as hydrogen bonding contribute to its high surface tension. Water molecules are able to form hydrogen bonds with neighboring molecules, creating a network of interconnected molecules at the surface. This cohesive force makes it more difficult to break the surface and results in a higher surface tension.
On the other hand, methylated spirit (ethanol with added methanol) has weaker intermolecular forces compared to water. Ethanol and methanol molecules experience intermolecular forces such as dipole-dipole interactions and London dispersion forces. While these forces allow for a certain level of cohesion, they are not as strong as the hydrogen bonds present in water. Hence, methylated spirit has a lower surface tension compared to water.
To experimentally determine the surface tension of water and methylated spirit, one can perform the following steps:
1. Prepare a clean, smooth surface, such as a glass plate or a penny.
2. Fill two small containers, such as petri dishes or cups, with water and methylated spirit separately.
3. Place the clean surface horizontally and slowly dip it vertically into the water.
4. Observe the curvature or meniscus formed at the point where the liquid touches the surface.
5. Measure the height of the meniscus using a ruler or caliper.
6. Repeat the same process with methylated spirit and measure its meniscus height.
7. Compare the heights of the meniscus between water and methylated spirit.
8. The liquid with the higher meniscus height will have the greater surface tension. In this case, water will have a higher surface tension than methylated spirit.
It should be noted that surface tension can be affected by other factors such as temperature and impurities present in the liquids. Therefore, it is important to ensure consistent experimental conditions when comparing surface tension between different liquids.