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July 02, 2020

Soap Suds and Science Fun!

Everyday we use things in our daily life that we don’t realize can be used to conduct science experiments! Soap is definitely one of them, that is found in all households. With the global COVID-19 situation, we definitely turn to soap now more than ever, but how else can they be used? Check out some cool experiments to teach your child more about surface tension, pressure and states of matter!

1. Pepper and Soap Experiment 

This experiment shows surface tension in action. All you will need is:

  • Pepper
  • Water
  • A flat dish or tray
  • Liquid dish soap

First, pour in some water to fill the tray. Then, sprinkle pepper over the surface of the water. Take note of what happens here – the pepper floats on the surface of the water due to the surface tension. Get your child to dip their finger into the center of the tray. What has happened? Nothing much. Now, rub a tiny amount of dish soap onto your child’s finger. Once again, get them to dip their finger into the center of the tray. What happens this time? The flakes of pepper should have been repelled to the edges of the tray, away from the finger that was dipped in! This is because the dish soap is formulated to break the surface tension of the water, and repel other forms of matter! In doing so, this is how grease and oils are cleaned away from the plates we wash when dish soap is used! 

Similarly, this is how germs are washed away with soap! Always make sure to wash your hands regularly and thoroughly during this COVID-19 season!

2. Expanding Soap 

This experiment requires only two items! They are:

Start by unwrapping the bar of ivory soap, and place it on a microwavable dish. Place the dish and soap into the microwave and heat for 1-2 minutes on a high setting. Get your child to watch what happens closely. 

The soap expands at a very rapid rate! Once the microwave process is complete, remove the dish from the microwave and allow it to cool for about a minute before letting your child examine the end product. The soap has changed to a puffy but yet stiff texture, which crumbles to powder when a light force is applied to it. If you have a spare bar of Ivory soap, allow your child to compare this soap to other brands of bar soap. Drop the bars into water to see what happens! Ivory soap should float while the others will sink due to the different densities of the soaps’ compositions.

*Note that this experiment MUST be done with Ivory soap or it will not work. This is because Ivory soap contains much more air than other bar soaps which allows the experiment to work. For further explanation, please click here

3. Colourful Repulsion 

This one is a sight to behold, and one that will leave your child feeling mesmerized! The simple experiment requires:

  • Food colourings of choice (red, blue and yellow are easy options!)
  • Milk
  • A flat dish or tray
  • A cotton bud
  • Dish soap

To start, fill up the flat dish or tray with some milk. Next, add in a couple drops of food colouring. Add in a few drops different colours to get an even greater effect. Try to spread the drops out so that the effect is more obvious later on when the experiment takes place. Do not mix in the food colouring! Then, dip one end of a cotton bud into some dish soap. With the end that contains the dish soap, dip the cotton bud into the middle of the tray with milk and food colouring and observe what happens! The colours in the food colouring should swirl together and “run away” from where the cotton bud is placed! This happens because the fat in the milk is pulled away from the other contents in the tray (i.e. the food colouring in this case) when the soap comes into contact with it. Similar to how a magnet works, the soap “attracts” the fat in the milk towards it, causing the fat to push other contents away when it comes towards the soap-filled cotton bud. Since fat molecules are larger but yet lighter than other water molecules, they are able to move towards the soap quickly. A process called ‘saponification’ takes place, where the fat (triglycerides) reacts with Sodium (or Potassium) Hydroxide that is found in dish soap, to form glycerol and even more soap.

We hope you and your child enjoy these educational activities! Should you and your child be interested in science and scientific endeavors, check our our YMCA Learning Centre STEM programme! This programme aims to spark an interest in students in learning how the world around us works, through experiential learning. Do contact us to find out more! 

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