Everyday Science: Soap
Who doesn’t love a hot bath? Well, lots of kids aren’t so happy about their encounters with soap and water, preferring to avoid cleaning behind their ears and between their toes. How to handle those reluctant bathers? How about exploring the mysteries of soap!
If you need some help in understanding how to use the steps in this activity, take a look at the “What is Guiding Curiosity” page.
Think of how to inspire conversation when taking a bath. Do any of the following questions help?
Where does soap come from or what is it made of?
How many different kinds of soaps are there?
Did the cavemen have soap?
How about the Ancient Egyptians, Greeks, Romans?
Were the Dark Ages called Dark because no one used soap to clean themselves?
How has soap changed over times in terms of ingredients?
Can we make soap?
What role does soap play in keeping us healthy?
How does soap work? (Soap is made up of molecules. Some of those molecules are attracted to oil, grease or dirt. Other molecules in soap are attracted to water. The first molecule attaches to the grease or dirt. When you rinse, the second type of molecule attaches to water and the dirt/grease is taken away. Water alone cannot usually get the dirt off. One needs the molecules in soap that grease/dirt can attach to).
Soaps are one type of detergent or included in the definition of a detergent. Detergents hold on to dirt and oils (grease) and then water washes them away. In the event that water does not wash it away, the result is soap scum.
Common everyday objects in hour household deserve a closer look.
Invite your child to find different kinds of soap in your home. Bar soaps of different shapes and sizes, dish soap, detergent for clothes, antibacterial soap, shampoos for humans and pets, cosmetic removers, and other non-alcohol-based cleaning products may qualify. Hand sanitizers do not count as they are alcohol based and not considered a soap (alcohol kills germs, soap removes them).
Feel, smell and look at these different soaps. Add water and stir or shake liquid or powder soaps. Wet a portion of skin and try out the bar soap. How does it feel and smell?
Find a store in your area that sells handmade soaps. Discuss the colors and shapes. Smell the different options. Which smells best or worse?
If your child can read, invite her to try and read the items on lists of ingredients included in common bath soaps. Colors, oatmeal, milk, vegetable oils, softeners, fragrances, are commonly added. Can she detect these ingredients by looking, smelling, or feeling?
Compare and Contrast
Comparisons inspire thinking and further exploration.
Compare the different shapes and sizes of soaps. Some are rectangular; others are square, oval, or round.
If you have multiple soaps of different colors, sizes and shapes, these can be used for classifying. Depending on your child’s age and the number of objects available, invite her to sort into two or three categories. Consider smell as an option for classifying. Soaps could be sorted as they smell good, neutral or bad.
Common everyday objects in your home are great for practicing scientific skills.
Visit a grocery store and count the number of soaps available. For example, count liquid soaps, bar soaps, or powered soaps. How many of each is there? If there are too many options, count only those that are green or red or on one shelf.
Measure the size of different bar soaps from end to end. Weigh a bar of soap. How much does it weigh? If you have a balance scale, compare bars of soap. Which is heavier? Try and predict a head of time which bar will be heavier.
Determine how much water a bar of soap can displace. Fill a kitchen bowl or other container with water to the top edge. Place that container in a pan so that any water that spills over the top can be captured. Place a bar of soap into the bowl. Some water should spill over the edge. Pour the spilled or overflow water from the pan into a measuring cup to determine how much was displaced when the soap was added. Fill the bowl again and try this with other items, or measuring the amount of displaced water in comparison to a bar of soap. If the object totally submerges or sinks, you are measuring the volume of that object/soap. If any of the object remains above the water line, its’ total volume is not displacing water, so you are only measuring a portion. But hey, the concept of measuring volume is still relevant
Your child already experiments with soap in the bathtub, although instead of the term “experiment” you probably refer to it as play.
How does soap work to clean things? After a meal, find a dish or pan that is dirty. If it has a grease spot on it, this will make the point most effectively. Run that dish under water. Is it clean? Again, a greasy dish or pan will prove the point. Now add soap to the dish or dunk it in soapy water. You may need to rub a little. What happens? The soap allows insoluble materials to become soluble and wash away.
Make your own soap. There are several recipes on line, but here is one that looks interesting. http://www.pbs.org/parents/crafts-for-kids/handmade-soaps/
This recipe uses glycerin that you can buy in craft stores. You melt it and pour into a mold.
If you want to use other ingredients there a number of alternative recipes on line. You can vary shapes, colors, and choose to put a variety of objects or toys in the soaps so they are more appealing to your child. You can also make soaps of different flavors including cucumber, tomato, and from carrot juice! Roses, lavender, and herbs are also common ingredients.
Homemade soaps can make great gifts.
As you make the soap, include your child in the process discussing how it works. If you use glycerin, discuss how you used heat to reduce a solid to a liquid. That liquid then hardens to become solid again. This is basic chemistry. Soap making is chemistry in that it involves treating oils or fats with an alkaline solution. Once again the specifics may be less important at this age than the idea that soap is a product of a chemical process. Chemistry is useful and interesting!
If you are making homemade soaps from oils and lye, it can take two or three days and up to six weeks for the soap to fully harden. This is a time frame during which your child is likely to forget what the purpose of the experiment was, so this activity may be more for parents or other caregivers than the children.
If a soap recipe includes lye you may need to proceed with some caution when children are involved. Only use lye with adult supervision and wear eye protection. But as the adult helper, you could handle the lye and allow your child to make decisions about the smell or shape of the soap and he can handle the safer ingredients.
Historically, soap was often made from tallow that is a beef fat. Next time you trim meat from a steak of roast, let your child handle it imagining how it might have been used to make soap. It will feel quite the opposite of the clean, non-greasy soaps we have available to us today.
Draw or create art with soap. Invite your child to think this through and invent a process of drawing with soap. You do not always have to provide specific instructions, just throw out an idea.
Here is one suggestion for using soap to create art. Mix some dish liquid with water in a ratio of about 3 to 1. Start with small amounts or about a tablespoon of dish detergent to 3 tablespoons of water in a small container. Add more as needed. Next add food coloring. Insert a straw and invite your child to blow bubbles. The bubbles should rise about the edge of the container so that you can place a piece of paper on the top. The bubbles will pop leaving behind interesting patterns. Use heavy paper or cardboard, as the lighter paper will get to wet and be difficult to handle.
A common suggestion on-line for an experiment with soap is to take a bar of Ivory Soap (other kinds will not work) and place it on a paper towel in the microwave for 2 minutes. Ask your child to predict what will happen. Perhaps cut the bar of soap in half so that you can repeat the experiment. To determine what happens, try another experiment or drop a portion of the bar of Ivory in water, what happens? Compare with another brand of soap dropped in water. What happens? Place the other brand in the microwave. What happens? Ivory soap is whipped more during production than other soaps resulting in pockets of air bubbles. Those air bubbles keep the soap afloat as compared to a denser bar of soap that sinks. When heating in the microwave, those same pockets of air bubbles turn to steam and expand.
Because Ivory soap floats, you can carve ship hulls out of it. Add sails and sailors for a voyage in the tub.
Experiment with soap bubbles. You can make a good bubble recipe starting with about 2 ½ cups of water. Add ½ cup of corn syrup and slowly add a cup or more of liquid soap. You can experiment with amounts or the types of liquid dish soap you use. Some recipes even call for cornstarch. You can also experiment with what is used for a bubble wand. I have seen suggestions using coat hangers, the plastic rings that hold together a six pack of sodas, string, colanders, or strainers. Look in your toy box. There is bound to be something that could prove interesting to use without having to purchase a new, relatively expensive toy.
Fill a bowl with water and find very light materials that will float. Try flower petals, dog hairs, Cheerios or other cereal pieces, or cotton balls to start. Float these on the water and observe their pattern. Do they move? Add a few drops of dish soap. What happens?
Create a small “powerboat”. From cardboard, cut out the shape of the hull of a boat. Or cut out any shape. Cut a small cut in one end. Slice a piece of soap and slide it into that crease. This is harder than it sounds. The soap tends to break up, so adult help will be essential. The soap slice should propel the cardboard shape through the water, or those molecules in the soap that do not like water should try to move away from it, while also moving the cardboard.
Hand washing with soap is fundamental to good hygiene and staying healthy. If your child is not already in the habit of regularly washing his hands, initiate this conversation about its importance and demonstrate good hand washing techniques. Why is it important to wash hands? How might it prevent germs from being transmitted from person to person? What is a germ? Watch someone else for a few minutes. How often do they put their hands near their mouth, eyes, or nose? What else do they touch that then they drink or eat from?
Most recommendations for good hygiene include washing hands for about the amount of time it takes to sing Happy Birthday or the ABC song. This is about 15 seconds. Invite your child to make up her own song for hand washing.
This discussion can extend to bathing and brushing teeth. After all, toothpaste is just another kind of soap.
Consider that bathing and using soap was relatively uncommon throughout much of Western history. Ask your child to imagine how people smelled when they were wearing the same clothes day after day that were not washed, and that those people didn’t bathe. It’s a good thing that we are all a little more conscious of the need to bathe so that we can live with one another and not regularly wrinkle our noses. Before bathing was common practice, perfumes were used to mask the smell. Now our soaps tend to be heavily perfumed just to be safe.
Historically, the Egyptians, Romans and Greeks all had some form of soap. However, it was more commonly used to wash cooking utensils and textiles rather than faces or hands. These ancient soaps were also used for medicinal purposes or to treat skin rashes, the very rashes that resulted from lack of hygiene in the first place
The Egyptians made soap from animal and vegetable oils and salts. They were also quite fond of aromatic oils, producing perfumed soaps. We would not recognize it as soap, nor would we recognize the smells, but yes, the Egyptians had a version of soap.
The Romans made some of their soap from urine. Yuck! In my book this kind of defeats the purpose of trying to get clean, but I am informed that urine is mostly water. Having said that, however, the Roman civilization was known for advances in hygiene, and the soap made of urine may have been used in treating textiles for cloth. Urine contains ammonia that is found in common cleaning agents. The Romans “bathed” by rubbing oil on their skin and then scraping it off along with any dirt. Romans also used urine to whiten their teeth. Ummmmmmm, right. Think I’ll take a pass.
After the Roman Empire fell, there was less emphasis on hygiene in the West. Think of the Dark Ages, and Black Death. In contrast, some Asian cultures continued to emphasize cleanliness as a means of staying healthy.
Egyptians, Greeks and Romans