Praxis: Erupting soap
By Medicine Hat News on September 1, 2018.
It is the last long weekend of summer and before many of us have to return to work and school! I know how hard it is going to be to get out of bed at the wee hours of the morning on Tuesday. The students are surely going to feel it as well. This week, I thought I would share one of my favourite experiments to “wow” those students so they know to sit up and take notice in your class. I hope this will keep them on their toes the entire semester. Let’s get started! *Remember to ask an adult before doing this experiment. Materials – one bar of Ivory soap – microwave – microwaveable plate – goggles Procedure 1. I cannot stress it enough — even with the simplest of science experiments we should always wear safety goggles. Please put them on! 2. Ask the students what they think will happen if you place the entire bar of soap in the microwave. 3. Place the bar of soap on the microwaveable plate and place it in the microwave. 4. Set the timer to “cook” for one minute. 5. Have the students gather around the microwave so they can observe what is happening. 6. Start the microwave. 7. Observe. 8. Pay attention to the microwave as they all have different powers. Once the soap has erupted into a large blob, stop the microwave and remove the plate with an oven mitt. Do not touch the soap for a minute or two it will be HOT. What is going on? In this experiment, yes, we actually are teaching about science, Charles’ Law to be exact. Charles’ Law states “the volume of a gas directly increases with an increase in temperature.” Simply put, as the hotter air gets, the more space it will take up and the more pressure it will produce in order to take up that space. Ivory is a unique brand of soap as it has a lot of air and moisture inside of it. If you do not believe me, we can expand this experiment by weighing the bar of soap before and after you erupt it. You will see that it weighs less after we “cook” it. When the soap is heated, you will observe that as it begins to soften and it almost looks like it is going to melt and then it erupts. This is because the moisture in the bar of soap gets so hot that it eventually turns to steam. Add this steam to the air pockets in the bar of soap and you have a great deal of steam trying to escape. As a result, the steam pushes out and eventually expands the soap into a fluffy eruption in the microwave. Educators please do not forget to book your Hands on Learning Kits and Scientists and Engineers in the Classroom for your school as soon as possible! Remember there is no cost to borrow materials from Praxis throughout the school year. Patty Rooks is senior scientific consultant at PRAXIS, “Connecting Science To The Community.” Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. 23-22
