Suppose the following scenario:
Winter, outside temperatures around 2-3 º C (32-33 F), inside temperatures between 18-20 ° C (64-68 F). Have you noticed that, when you fill a balloon inside the house, and you take it outside it shrinks? Like as if he had lost air? And if you bring it back into the house it recovers the shape? This phenomenon is more visible when the balloon is filled with He.
Physics explain this.
To explain this our young restless minds, let's see this demonstration:
What we need:
- big balloon, for best results blow up the balloon and let the air out once or twice,
- bowl, preferably metal
- ice, enough to fill the bowl
- empty plastic bottle,
- Flexible measuring tape.
- Blow the balloon, enough for it to stand up;
- Without allowing the air to escape, hold the mouth of the balloon to the neck of the bottle, use the tape if needed;
- With the tape measure the circumference of the balloon;
- Fill the bowl with ice and a little water, not much, 3 to 4 fingers high, we want the water to be as cold as possible but the contact surface with the bottle must be the largest possible;
- Place the bottle in the bowl and wait a few minutes;
- Re-measure the circumference of the balloon. With luck it will be sucked into the bottle.
Apparently the balloon will shrink. Sometimes is sucked into the bottle.
As seen in Egg in a bottle, before the bottle is placed on the bowl with ice water, the air inside it- and the balloon- was at same temperature as the air outside. When we place the bottle on ice the air will cool and therefore contracts. At this point the pressure in the bottle is lower then the pressure outside, and the laws of physics kick in pushing the balloon into the bottle.
This demonstration when done in optimum conditions shows the balloon being sucked into the bottle.
Can you blow the balloon again without touching it?