We love to blow things up around here. But what about sucking things in? This is an experiment that often surprises the kiddos because they don’t often get to see a balloon get pulled inside out. Ready to startle the kids? Let’s get started.
Total Time: About 10-15 minutes
Safety Concerns: Be careful around hot water. At one point the glass bottle does get warm from the hot water, so just make sure that it’s not so hot as to burn fingers. Use oven mits if necessary.
Materials You Need:
A glass bottle
A balloon with the neck cut off (This is apparently necessary. We tried it several times without cutting the neck off and it didn’t work.)
Large bowl full of ice water
- Fill the glass bottle with warm water. We heated the water up on the stove and then poured it into the bottle, but hot tap water is probably fine, too. No need to use boiling hot water. See Safety Concerns above.
- Leave the bottle for a few minutes so that it gets warm. Pour out the water.
- Stretch the balloon over the top of the bottle.
- Stand the bottle in the bowl of cold water.
- What happens to the balloon?
So what is going on here?
When air is heated up the molecules in the air have more energy to bounce around. This increases the pressure, or expands the air. When air gets colder the molecules slow down and move less, which decreases the pressure and makes the air contract, or get smaller.
In this experiment we first filled the bottle with warm water, which heated up the bottle and the air inside. As we cooled the bottle down, the air inside cooled down and contracted, or took up less space. To make up the extra room in the bottle, air from outside pushed into the bottle, which pushed the balloon into the bottle as well. Another way to explain this is to say that we created a vacuum in the bottle, which sucked the balloon into it.
Cool, right? Try this with different sized containers, get really scientific and use a thermometer to measure the temperature of the water, or keep track of how long you need to cool down the bottle before the balloon gets sucked into it. Have fun!