Why Soap Works to Stop the Corona Virus …with activities

Soap is much better at stopping the Corona virus than alcohol. In this lesson, I may use the word “kill” for impact, but nothing actually kills viruses, since they aren’t alive. But you can blast them apart so the little buggers can’t harm you.

Soap has been used for centuries…how did people come to discover it? One theory says that it was discovered at the foot of mountainside altars where animals were sacrificed by burning. Fat and ashes accumulated in the clay soils around the altars. People in the middle east still use types of clay for washing and women might have gathered some of the clay near the altars for doing their laundry at the river. They noticed that the clay mixed with water, fat and ashes cleaned better than clay alone. Water, fat and lye from ashes is a basic pioneer recipe for soap. Author’s note: I bought some bars of clay for washing in the street markets of Afghanistan.

Here’s the thing about soap molecules: one end of the molecule likes to attach to water; and the other end is repelled by water. The hydrophobic (water fearing) end attaches to dirt and grease. The water-loving end (hydrophilic) attaches to water molecules. We haven’t gotten to the virus killing aspect yet.

Here’s a drawing I like to show students about the soap molecule. After explaining, we play a game.

soap molecule dirt water

Activity: Soap grabbing dirt game

I play the part of a soap molecule and the children are dirt and grease. I point out a door which represents a sink drain. I run around the room, with one hand held out looking for a water molecule (which might be imaginary or could be another teacher) and my other hand grabs onto children (dirt and grease) in a long chain. Soon we are running around the room, the soap molecule having scooped up all the dirt and grease. Then my other hand finds the water molecule (I’ve either explained that it’s imaginary or I grab onto another teacher who plays the water) and we are all flushed down the sink and out the door. They love playing this game, giggling at being dirty grease.

kids playing soap game

Activity: Get Dirty

A natural follow-up activity is to ask the children to get their hands really dirty (how fun!) and then use a bar of soap and water to wash themselves clean – then watch the dirt go down the drain.

At the end of this post are other activities that involve soap.


But now, why does soap kill the corona virus? You remember the water-loving end and the water-avoiding end of the soap molecule. Ah. The hydophobic end (water-avoiding) not only picks up dirt. It can also puncture a virus membrane, splitting it apart. Presto: virus destroyed. Soap is the only ingredient that is so effective at ruining virus. It is good at splitting apart the molecules of that membrane.

soap molecule killing corona virus

When you wash your hands using plenty of water and soap, and then completely rinse the water down the drain, the dirt and virus bits are taken with it. Of course, this only works on skin you have washed. You might want to wash your face, too.

Activity: Wash with various water mixtures instead of plain water

Not all waters are equal. Try sudsing your hands first with tap or well water. Observe the amount of suds – or better yet – watch as someone else suds their hands and draw what you see for reference or take a photo. Then try washing your hands with salty water or water with dissolved epsom salts. Is there a difference? Which would be most effective at cleansing? The more suds, the better the cleansing effect.

Activity: Wash your hands with soap root.

This California native plant grows everywhere along roadsides and pastures. The leaves are long and wavy. The bulb can be dug up with a pickaxe. Remove the hairs from the bulb. Have a tub of water ready. Mash up the bulb using two stones. Put the mashed up pieces into the tub of water and rub vigorously between your dirty hands. Suds! Note: I tried washing with soaproot for years unsuccessfully by simply rubbing the bulb between my hands. Nothing. It is only when you crush it that you release the saponins. Experiment makes perfect!

saoproot leaves

soaproot bulbs

Activity: Make Jelly Soap

Here’s a sorta silly recipe, but one that might encourage kids to wash their hands more often: Jelly Soap.

Pour 1 Cup boiling water over one pouch unflavored gelatin (.25 ounce). Stir to dissolve. Then slowly add 1/2 Cup liquid hand soap into the gelatin mixture, stirring very gently because you don’t want bubbles. Food color is optional. Pour the mixture into silicone molds and let set overnight. If you don’t have silicone molds, just pour it into any small cup and scoop it out the next day when it has set.

jelly soap
jelly soap

Search for a long-lost recipe…and hours of unsuccessful (but fun) experimentation:

When I was a Girl Scout leader in the 1990’s, I came across a science experiment in the Brownie Scout manual which I followed successfully in both my troop and science classes. The basic idea was to mix salt with liquid soap. The soap would curdle and solid chunks float to the top, which could be scooped off and molded into new “bars” of soap.  The science wasn’t explained in the Brownie manual, but I researched it and discovered it was an excellent connection to chemistry and the history of Castile soap. Castile soap historically was a liquid soap made in Spain from olive oil and the ashes of plants such as pickle weed found in salt marshes. These ashes produced potassium hydroxide and the resulting soap is always liquid. But liquid soap was difficult to transport and it was desirable to find a way to make it solid. Now we know that ashes made from hardwood produce sodium hydroxide and the resulting soap is solid. But the producers of liquid Castile soap hadn’t discovered that. Instead, they discovered that adding salt to liquid soap would curdle it, which they could mold into hard soap. Voila! That was exactly what we were doing when we added salt in my Brownie troop.

Alas, I cannot find that experiment anywhere on the internet and I no longer have that out-of-date Brownie manual. It was so fun, easy, and historic. I spent hours over the past couple of days researching and experimenting on my own and did eventually find that I could add salt directly to Dawn dishwashing detergent and come up with a sort of goo. Here’s a photo. If anyone has an old Brownie manual, I’d love to find the original experiment. You might also want to try adding salt to various liquid soaps and see what happens.

dawn and salt goo







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