A demonstration of air pressure


1. Two water glasses of same size
2. A candle
3. A piece of paper wider than the glasses
4. Something to light up the candle


1. At first make a hole in the middle of the piece of paper and make it wet by using water.
2. Put one of the glasses upwards on the table and put the candle inside the glass.
3. Now cover the top of the glasses using the piece of paper so that the hole of the paper and the burning are in parallel.
4. Put the second glass downwards on top of the first glass.
5. Wait until the candle burns out.
6. After the candle burns out, try to separate the two glasses from each other.


When you try to separate the two glasses from each other you will surprisingly see that those glasses are a bit tightly stuck together and you can’t separate them very easily.


When the candle burns the oxygen trapped inside the glasses is reduced. It keeps reducing until the candle burns out. The oxygen level becomes zero when the candle burns out. So now there is less air or gas in the glasses and for that a vacuum is created. That’s why the gas or air pressure inside the glasses is reduced but the gas pressure outside remains the same. Due to the air pressure outside the glasses becomes stuck!


Air creates a force on every object because its moving molecules are constantly colliding with those objects. Air pressure is the measurement of this force. The pressure of the open air is normally called the atmospheric pressure. It is lower in high altitudes because in higher places the air is less dense. But the more lower we go the air pressure or the atmospheric pressure becomes more and more because the air is much more dense. It is also because all the heavy gases are found in the lower part. Now that you know about the air pressure I will explain about our project a little bit more. The air inside the glasses will always try to get outside and the air outside will try to get in. But the wet piece of paper will prevent this from happening. When we put the glasses together to form a magdibard glass some air gets trapped inside and forms an internal air pressure of its own. The air pressure of the inside and outside is the same then. But when some of the oxygen is reduced due to the burning of the candle the air pressure outside becomes grater. So the air pressure outside dominates the internal air pressure and press the two glasses. That’s why it is so hard to separate a magdibard glass.


1. Try forming the magdibard glass by using a dry piece of paper.
2. Try forming the magdibard glass without using any kind of paper.


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