Science Smarts: Cartesian divers under pressure
By PATTY ROOKS on May 28, 2022.
I have been busy planning some of the hands-on activities for our 30th anniversary celebration coming up on June 18 at the Carriage House. This has to be one of my favorite things to do – it is so much fun trying out activities to see if they will work for a variety of age groups. My test subjects are often agreeable when it comes to fun “chores” like this as well. Here is one that I think will be a hit. Let’s get started! Remember to ask an adult before doing this experiment Materials • Empty 500 mL water/pop bottle with a lid • Water • Medicine dropper/pipette • Brass hex nut Procedure • Fill the water bottle almost full of water. Set aside. • Place the brass hex nut on the thin end of the pipette. Push it all the way up to the top just underneath the bulb. Sometimes if you give it a twist it will stay in place. You do not want it to fall down so try your best. • The hard part now…squeeze the bulb of the pipette and fill it about ¾ full of water. Place the pipette in the water bottle. You want the pipette to float freely in the water. If it sinks to the bottom, remove the pipette and squeeze out a bit of water and try again until it floats in the water. • Put the lid on the water bottle. • Squeeze the water bottle and let it go. • Observe what happens. What is going on? This experiment demonstrates the principle of buoyancy. When you squeeze the bottle, the diver should sink and when you release the sides, the diver should float to the top. There is just enough “air”in the Cartesian diver to make it positively “buoyant.” This allows the Cartesian diver to float on the surface of the water. There is a great deal of science going on in this experiment, but I do want to keep it simple. Simply put, when you squeeze the bottle, the pressure in the bottle is increased, therefore the volume of air trapped inside the Cartesian diver decreases. As the volume of air decreases, water is taken up into the Cartesian diver which increases the density of the Cartesian diver so it sinks. Keep an eye on our social media as we have officially kicked off our 30th anniversary celebrations. June will be a busy month and we hope you will join us for this FREE community event on June 18 between 10 a.m. and 3 p.m. for our official celebration at the Carriage House. Patty Rooks, Senior Scientific Consultant PRAXIS, “Connecting Science To The Community”. Contact with Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. Address: #12 826 11 Street S. E., Medicine Hat, Alberta, T1A 1T7 Phone: 403.527.5365, email: praxis@praxismh.ca 21-20
