This weekend my TEFL students will perform the following three science experiments at Pakuwan Mall in Surabaya. We have spent the last two weeks studying air and water pressure, pitch, and forces, and now must demonstrate our knowledge of these things for the parents and everyone else in attendance. It should be a fun and memorable event. So, without further adieu, here is the first experiment:

1. Glass Water Trick.

Glass Water Trick

The water bottle is full of water… but the notecard sticks to the opening! Is it magic?? Or science? Hmmm…

This is by far the easiest and coolest of the three experiments, which is why we’re performing it first. Take any kind of glass (even a water bottle will work) and fill it with water. Then, hold a notecard at the top and turn the glass over, making sure no gaps form between the card and the top of the glass. (It must be a tight seal.) Instead of water gushing out, the notecard will stick to the glass, functioning sort of like a lid. Science is cool. 🤘

In a nutshell, it works because the air pressure pushing against the outside of the card is heavier than the pressure coming from the water and air inside the glass.

2. Harmonic Water Bottles.


No need to spend money on fancy musical instruments… just get some water bottles!

I’m most worried about this one… because one cannot just blow into a bottle and create a note. The angle matters. But all you need for this to work are five water bottles filled with different amounts of water. When you blow across the top, the pitch will be different based on the amount of water inside. The less water, the higher the pitch.

This works because sound is produced by vibration, and when you add water into the bottle you slow down that vibration, creating a lower note. (I would like to create the theme of Close Encounters, but I may have delusions of grandeur.)

3. Balloon Rockets.


Anything with ‘rockets’ in the title will get the boys interested.

This is the one the boys fought over. It is the grand finale and the most complicated of the three. Take a long piece of string and slide it through a straw. Tie one end of the string to the leg of a chair, then tie the other end to another chair a couple meters away. Move the chairs apart to tighten the string. Next, blow up a balloon and seal it shut with a paper clip. Finally, tape the balloon to the bottom of the straw. Repeat the procedure with another balloon on the other side of the chair. You now have two balloon rockets ready to race each other!

Believe it or not, this experiment demonstrates Newton’s Third Law of Motion: for every action there is an equal and opposite reaction. When the paper clip is removed, air escapes the balloon (the action), causing the balloon to move (the reaction). Thus, the escaping air acts as the force that puts the balloon in motion.

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