Killing enveloped viruses with soap
Soap molecules are amphiphilic. This means they have parts which are hydrophilic (water-loving, or &quot;polar&quot;) and parts which are hydrophobic (water-avoiding, or &quot;non-polar&quot;).
Fat molecules are non-polar. They avoid water. This is why a mixture of oil and water will separate into layers. In this mix, oil molecules prefer to hang around other oil molecules, and water molecules prefer to hang around other water molecules. Soap &quot;likes&quot; both oil and water, so it can be used for cleaning, by helping dissolve this mixture. (For a similar reason, this is why vinegar is used to dissolve or emulsify oil in salad dressings.)
The coat of an enveloped virus is made up of layer of phospholipid molecules and proteins. Phospholipid molecules are similar to detergents, made up of polar and non-polar ends. These lipids arrange themselves into a two-layered sandwich called a &quot;bilayer&quot;. The polar ends of this sandwich are the &quot;bread&quot;, while the fatty non-polar ends are the &quot;filling&quot;.
Detergents can help disturb this by pulling or dissolving out phospholipids from the virus coat to form micelles, tiny bubbles of fat and soap that can be washed away. This puts holes in the virus coat and helps dissolve it.
The insides of the enveloped virus particle cannot infect directly and must rely on its envelope to get into and infect a cell, so breaking down the coat inactivates (or &quot;kills&quot;) the virus.
Alcohols are also amphiphilic. There are many different alcohols, but they all have a hydroxy group at one end, which is polar, and a saturated or partially-saturated carbon chain on the other end, which is non-polar. Like detergents, this property allows an alcohol — at a sufficient concentration — to disturb and break down the virus envelope phospholipid bilayer, inactivating it.
Non-enveloped viruses lack this phospholipid bilayer coating and are instead protected by a protein capsid. The proteins in a capsid will not dissolve with detergents, but they can be attacked with other disinfectants that chemically denature the proteins. Examples of such disinfectants are chlorine (bleach), iodine, peroxides, etc.
Just as soap can put holes into the phospholipid coating around enveloped viruses, destabilizing them, denaturing agents change the structure of proteins that protect non-enveloped viruses, also destabilizing the capsid. If the capsid proteins are damaged sufficiently, the virus particle is not able to infect a cell and so is deactivated.