Did you know that you can crush a bottle just by thinking about it? (Well, that and a little science!)
Materials
• Hot water from the tap or heated on the stove or in a microwave
• Plastic water/soft drink bottle (#1 - PET recycled plastic) with a screw-on cap. Hint: The flimsier the plastic, the more drastic the results will be.
• Optional: Ice water
Be Safe!
Adult supervision is necessary when working with hot water.
Experiment
Pour hot water into the bottle until it is about one-quarter full. Put the cap on and shake the bottle to disperse the hot water throughout the bottle. Do this for about 10 seconds. Take off the top, pour out the hot water, and quickly recap the bottle. Set the bottle down and observe what happens. Your observations should include both what you see AND hear! For a more dramatic effect, place the bottle in ice water, the freezer, or outside in a snowbank.
What’s happening?
If someone asks you what’s in an empty bottle, what would you say? Ideally, your answer would be air! There are MANY molecules of nitrogen and oxygen gas (air) in an “empty” bottle. Adding hot water to the bottle causes those gas molecules to heat up.
As you heat up the gas molecules they also begin to move faster and take up more space. When you then pour out the hot water and recap the bottle, you’ve now trapped those hot air molecules in the bottle. Before long, the molecules begin to cool and slow down, which reduces the pressure of the gas molecules inside the bottle. As this happens, the normal air pressure outside the bottle continues to press on the bottle at a force of 15 pounds for every square inch of the bottle’s surface area. That is equal to about 850 pounds of force on the outside of the bottle. So, if there were no air molecules left inside the bottle, you could imagine that the bottle would be totally crushed. Because you didn’t eliminate all the air molecules, the bottle only partially collapses. Now, if only you can convince your friends that you crushed the bottle using only your mental powers!
References
https://spark.iop.org/collapsing-bottle
To view past “ChemShorts for Kids” activities, go to:
https://chicagoacs.org/ChemShorts
