# Why does a water bottle or 20 or 25 litre jar can suck the air and form bubbles inside when you pour the water from it?

## When you pour the water from a bottle making the bottle upside down the water comes out and there is a space created inside the bottle. That space has no air and it is called vacuum and the pressure of air is zero. Naturally, air flows from high pressure area to low pressure area automatically without any external force. Nature always tries to maintain a balance. So the outside air which is at one atmosphere pressure rushes inside the bottle to fill the space to balance the pressure. This forms the bubble and makes the water to come down slowly.

When you pour the water from a bottle making the bottle upside down the water comes out and there is a space created inside the bottle. That space has no air and it is called vacuum and the pressure of air is zero. Naturally, air flows from high pressure area to low pressure area automatically without any external force. Nature always tries to maintain a balance. So the outside air which is at one atmosphere pressure rushes inside the bottle to fill the space to balance the pressure. This forms the bubble and makes the water to come down slowly.

Explanation:

Movement of the air:

Air always moves from high pressure region to low pressure region automatically without any influence. This is the general tendency of the nature to balance the environment. For instance, in summer season snow melts and in winter season water again becomes snow. There are more examples for these tendencies of nature.

Often we feel air is moving around us. This is because air is moving from high pressure region to low pressure region.

Why is the air sucked inside the water bottle?

When the water tries to come down there is a gap created inside the bottle. This space will have no air and so no air pressure. So to balance this no or low pressure condition the high pressure air from outside the can will try to rush inside the can through all possible ways. If there is no way for the air to enter inside the water from the can won’t come down further. If there is any way for the air to go inside the air will go and the water comes out.

So at the same time the water will come out through the mouth of the can and the air will go inside. The water will come down slowly due to this reason.

Experiment:

Take a water bottle and fill it with the water. Close the mouth of the bottle with the cap very tightly so that no air will go inside the bottle.

Now put a small hole using the needle at the bottom of the bottle.

If you see no water will go out. Because through this very small hole the air cannot go inside and the water cannot come outside simultaneously.

If you open the cap of the bottle the water will comes out forcefully through this hole. Because the air fills the can through the top and the water comes at the bottom.

Summary:

From this experiment we understood that if the water has to come out the air has to come out. In the same way if the bottle has to be filled with water the air inside the bottle should come out.

This same concept is used in the automatic water bottle filling machines in the industries to fill the water.