Science Smarts: Create your own witches brew
By PATTY ROOKS on September 18, 2021.
Once again I was browsing the shops as I was running errands this week, and I found the best little Halloween themed Erlenmeyer flasks. I thought these would make the best container to hold my “witches brew” for Halloween. This could get messy, so make sure you cover the table with a disposable tablecloth for easy clean up. Let’s get started! Remember to ask an adult before doing this experiment Materials • Instant yeast • Hydrogen peroxide (ideally 35% or food grade but any will work) • Water • Food colouring • Liquid dish soap (blue) • Measuring cup and spoon • Mixing cup • Stirring spoon • Safety goggles • Rubber gloves • Disposable table cloth Procedure • Cover your work area up with the disposable table cloth. This could get messy! • Put on your safety goggles and rubber gloves. • Place the flask on the table. • Measure and pour 125 mL of hydrogen peroxide into the flask. • Add a few drops of food colouring. I like green. • Squirt in three nice streams of the liquid dish soap. I know really scientific, but we do not need to be precise here. • In a separate mixing cup, measure 10 mL (two teaspoons) of dry yeast. Add 30 mL (two tablespoons) of warm tap water. Stir well. If there are still lumps do not worry. • Get ready – I like to have a countdown from ten and then you are going to pour the yeast mixture into the hydrogen peroxide mixture. STAND BACK. • Observe. • Clean up OR repeat! • Make sure you wash your hands when you are finished as the hydrogen peroxide may irritate them. What is going on? This experiment should have made quite the explosion ALL OVER. If it did not, troubleshoot your experiment. The most common problem I find is that the hydrogen peroxide is no longer working and you may need a new bottle. It can denature quite quickly after you open the bottle. The science behind this amazing eruption is that you produced an exothermic reaction. This sounds pretty complicated, but essentially, you created heat. If you hold your hands close to the foam or even observe, you will see steam coming off of the foam. You also created a LOT of foam. When you mixed the yeast (which is a catalyst) into the hydrogen peroxide, it removed all if the oxygen from the hydrogen peroxide causing it to erupt out of the flask. Keep reading each and every week for more amazing Halloween Experiments! Do not forget to get your applications in for the APAR Initiative STEM and Leadership Cohort for 2021-22. Praxis only has a few spots left and the deadline is fast approaching for this great opportunity for females in Grades 6-9. Patty Rooks, Senior Scientific Consultant PRAXIS, “Connecting Science To The Community” 34-33
