Water does not easily remove grease from dirty hands because grease is nonpolar and water is polar; therefore they are immiscible. The addition of soap, however, results in the removal of the grease. Examine the following structure of soap and explain why soap works.
CH_3(CH_2 )_16 C-O^-Na^+
nonpolar tail Polar head sodium stearate a soap
Soap is made up of molecules called surfactants, which have a unique structure that allows them to work as effective cleansers. The structure of soap consists of a nonpolar tail and a polar head.
The nonpolar tail of soap is made up of a long chain of carbon and hydrogen atoms (CH3(CH2)16), which is hydrophobic or water-repellent. Grease and oils are also nonpolar, meaning they are not easily soluble in water. This is why water alone cannot effectively remove grease from dirty hands, as water molecules are polar.
The polar head of soap (-C-O^–Na^+) contains a carboxylate group (–C-O^–) with a negative charge, known as the polar or hydrophilic part of the molecule. This polar head is attracted to water because water molecules are also polar. The sodium ion (Na^+) is present to neutralize the negative charge of the polar head.
When soap is added to water, the hydrophobic tails of the soap molecules are repelled by water, causing them to cluster together, forming structures called micelles. In these micelles, the nonpolar tails face inward, shielding themselves from water, while the polar heads face outward, interacting with the surrounding water molecules.
When dirty hands are washed with soap and water, these micelles effectively trap grease and oil molecules within their nonpolar core. As the water is rinsed away, the micelles with the trapped grease are carried away, resulting in the removal of grease from hands.
The polar head of the soap molecules also allows them to interact with water, facilitating the rinsing process and ensuring the removal of both soap and grease from the hands.
In summary, soap works by forming micelles that encapsulate nonpolar grease and oil molecules, making them soluble in water and allowing for effective removal during rinsing. The polar head of soap interacts with water, aiding in the rinsing process.
Soap works to remove grease because of its unique structure, which allows it to interact with both water and grease.
In the chemical structure of soap, there is a long hydrocarbon chain (represented as CH3(CH2)16) known as the nonpolar tail. This hydrocarbon tail is nonpolar, meaning it lacks an electric charge and does not readily dissolve in water. Since grease is also nonpolar, the nonpolar tail of soap is attracted to the grease molecules.
On the other end of the soap molecule, there is a polar head (represented as C-O^-Na+). The polar head contains an oxygen atom (O) and a negatively charged ion (O^-) with a sodium ion (Na+) attached to it. The polar head is hydrophilic, meaning it is attracted to water molecules.
When soap is added to water, the polar heads of soap molecules align themselves towards the water, while the nonpolar tails are repelled and move away from the water. This alignment of soap molecules forms structures called micelles. In a micelle, the nonpolar tails are grouped together in the center, effectively trapping the grease molecules within the micelle's core.
The polar heads of the soap molecules facing outward make the entire micelle soluble in water. These micelles continuously surround and suspend the grease particles in the water, allowing them to be easily washed away.
So, the combined structure of soap with a nonpolar tail and a polar head enables it to interact with both water and grease, making it an effective agent for removing grease from dirty hands.