Soap. It’s become the new gold in supermarkets since COVID 19 turned our world upside down.
In recent years we’ve been bombarded with advertisements for soap alternatives. There are all sorts of fancy hand sanitisers, wet wipes, and sprays on the market.
But it turns out that good, old-fashioned soap is the key to washing dirt and germs off our hands and down the drain.
So, from a teacher and science-nerd, try these experiments to see why every bubble needs a little soap these days.
What is soap?
I looked up soap in all the dictionaries. It’s a “a substance used with water for washing and cleaning,” Oxford says.
And Merriam Webster adds that it’s made by the “action of alkali on fatty acids.” And that it consists “essentially of sodium or potassium salts of such acids.”
Is soap salt? Now, I wouldn’t have guessed that.
Yet, in chemistry, it’s pretty straightforward. Base + Acid = Salt.
Of course, I’m not talking about the salt you sprinkle on your food. It turns out there are many types of salt in the world, and soap is the vital one right now.
How Is Soap Made?
You need three ingredients — lye, oil and water.
Lye is a base. It has a pH of 14, which makes it extremely caustic. You don’t muck around with lye — treat it with respect because it’ll burn your skin if you don’t. Fortunately, once you’ve made your bars, there’ll be no lye left in the soap.
Oils are actually acids. Soap makers usually use a mixture of oils, e.g. olive and coconut, to create a bar which will lather up but still set in the mould.
Water: lye and distilled water are carefully combined, and there is no room for error here. You need exactly the correct amounts to make the soap work.
Extras: you can, of course, add scents, colours even herbs etc. to make the soap look and smell nice.
How Does Soap Clean My Hands?
Well, it’s all to do with the fascinating way parts of a soap molecule fit together.
One end of the molecule is hydrophilic, which means it’s highly attracted to water. But the other end of a soap molecule can’t stand good old H₂O; hydrophobic is the technical term.
Talk about opposites attract.
In practical terms, it means that soap forms a bridge between dirt (which clings to surfaces) and water. It loosens the dirt and shunts it into the water. There it stays, to swish down the drain as soon as you pull the plug.
Planet Science has a simple but effective experiment to show how this works.
Why Is Soap Effective Against Viruses?
A virus is a microbe that can’t replicate itself until it invades the cells of a living being. It’s made up of three parts: RNA, proteins and lipids.
- Proteins help the virus break into the cell and help it replicate.
- RNA is the viral genetic material — that’s what it wants to multiply.
- Lipids form a protective coat around the virus.
Together these viral ingredients stick together like velcro. Once they get in, they’re hard to stop.
But, soap loosens the lipids and dissolves the bonds holding a virus together. It literally falls apart. And, just like the dirt, you can wash it harmlessly down the drain.
Best Hand-washing Techniques
Follow these five steps every time.
- Wet your hands and the soap bar with clean, running water, then turn off the tap.
- Lather your hands by rubbing them together with the soap. Rub all over the backs of your hands, between your fingers, and even under your nails.
- Scrub your hands for at least 20 seconds. To time it, sing the Happy Birthday song through twice.
- Rinse your hands well under clean, running water.
- Dry your hands using a clean towel or air dry them.
The Longest 20 Seconds
My hands have never been so clean before. But I’m getting mighty sick of “Happy Birthday,” aren’t you?
So, I found a few catchy alternatives:
Or you could count in another language. Now’s the time to finally nail the numbers in Maori, French, Spanish, Japanese…
Or, if you’re going stir crazy you might just want a mantra.
“Keep calm! You can do it. This too shall pass. (4x slowly should do the trick.)
Soap And Water Experiments
I used to do surface tension experiments every time I taught a new class. There are so many variations to these, and they’re as fun for adults as children.
- You need a new dish of water each time you do an experiment.
- And here’s a teacher tip — try an experiment yourself before you do it with your kids. They aren’t always as easy as the videos make it look.
Here are a few of the best:
Watch this simple experiment by yourself, so you know what to do. Then surprise your children with its magic. Ask for their ideas before you explain the science behind it.
Extend The Experiment
- Find some other safe household liquids (oil, vinegar, milk etc) and test the strength of their surface tension.
- Use other forms of soap to see how they work compared to dish washing liquid.
And if you’re running out of pepper, make a new experiment to test other safe household ingredients that are hydrophobic (repel water.)
Step up the experiment stakes by making boats that work on soap power.
Science Bob recommends dishwashing liquid on a toothpick, but I used to collect leftover slivers of soap and wedge them into the ends of my boats.
Extend The Experiment
- Experiment with size. Get the kids to come up with questions such as: Does a bigger boat need more soap? What size boat works best?
- Stage some boat races. Think about why each boat needs its own tray for this. Here’s a great opportunity to talk about why the trays need to be the same size. (The basic scientific principle is to keep variables the same and change just one per experiment. It’s called making a fair test.)
Make Artful Bubbles
There’s a whole world of bubble-filled art out there. Here’s one easy way to do it.
And if you think this is just for kids, check out this Czech artist who takes it to a whole new level.
Finally, here’s a heap of soapy art ideas from Kids Activities .Com