1The boiling point of water depends upon the ambient pressure and is directly proportional to this pressure. The vapor pressure of water is 23mbar, therefore when ambient pressure on the open end of glass beaker having some water in it, placed in a glass bell jar is decreased to this value; water starts boiling at room temperature even at a temperature lower than its normal boiling point without any heating and continues to boil at lower pressure as well.


2Rubber balloon expands due to the pressure difference across its wall either by increasing the pressure inside the balloon or decreasing the pressure outside it and this expansion is directly proportional to the pressure difference. You can see this effect visually in this practical demonstration.The pressure difference across the wall of partially inflated balloons kept in glass bell jar increases, the size of the balloons increases accordingly. Consequently, if the created pressure difference is nullified, the size of balloons will be decreased correspondingly.


3In this demonstration, a partially inflated balloon is placed in a small diameter pipe beneath the slim flag stick and pressure outside the balloon in the pipe is decreased. As the pressure difference across the balloon wall increases, its size increases, raising the flag up. Conversely, when the pressure in the pipe outside the balloon increases, the pressure difference decreases, causing the balloon to shrink which bring the flag down.


4A critical chemical under special environment can be transferred from container A to container B by creating vacuum on the open-end of container B, placed in closed glass bell jar. Conversely, the same chemical is re-transferred to the preceding container by applying pressure on the same open-end of container B.


5Sound needs some medium or air for its transmission. In this demonstration, a mechanical bell is installed in a glass bell jar. When the bell jar is at atmospheric pressure, the full sound of bell can be heard. If the bell jar is put on evacuation, the sound of bell slowly becomes dimer and dimer according to the level of evacuation and finally vanishes. If the generated vacuum is nullified, the sound of bell can be heard again.


6The breathing process in human body is supported by a dome-shaped muscle under the lungs, acting like diaphragm pump. The diaphragm contracts downward, creating vacuum that causes the inhalation of Oxygen (O2) into the lungs while the opposite action bases the exhalation of Carbon Dioxide (CO2) from the lungs. Human being pumps to about 740Torr by breathing and 300Torr by suction, whereas atmospheric pressure is 760Torr.


7In this case air is uplifting force of fluid; called buoyancy force, which is directly proportional to the size of an object. In this demonstration, area of bell jar is large for ball and small for weight. When the bell jar is evacuated, this force vanishes more beneath the ball and small beneath the weight, resulting the bar of the balance to tilt.


8A small filament is installed, constantly heated by current power supply. When there is atmospheric pressure in the glass bell jar:The level of gas particles, collision with the filament and heat removed from the filament is high, so filament settles at low temperature. On evacuation, when there in minimum number of gas particles, minimum number of collisions with the filament, minimum heat removal from the filament, thus filament settles at high temperature. It is quite obvious that when pressure was high, the temperature was low and vice versa. This principle is used for the measurement of vacuum in a thermocouple gauge.


9In this setup, there is a closed glass annulus which is evacuated by opening the evacuation valve. Its inner diameter side is heated with heating tape and a temperature sensor is attached to this side. Another temperature sensor is attached to its outer side of the annulus. Temperature difference between the two sides of the annulus is observed, showing that vacuum space is acting as insulator.


10In this arrangement, there are two glass chambers A and B connected by a glass tube. Chamber A is filled with some material grains with its open end at atmospheric pressure while chamber B is connected with the evacuation port. When evacuation valve is opened, the material grains transfer from chamber A to chamber B due to pressure difference, which can easily be seen in the glass made prototype.


11In this bell jar, two occurrences will be demonstrated. Firstly, Oxygen is required for to lit the candle. When bell jar is evacuated candle flame goes off. Secondly, smoke is heavier than vacuum, it goes down in vacuum environment instead of rising up as in normal atmosphere.


12A model of train is placed in a glass tube. When pressure difference at both ends of the glass tube is applied, the train moves left and right between two points according to the direction of applied pressure difference. Basically this practice can be used for the facilitation of mail or small goods transportation at different points in a sophisticated setup.


13In this experiment,  pair of hemispheres are arranged typically placing rubber seal between them. When the interior of hemispheres is evacuated, the created vacuum seals together the hemispheres with a remarkable force and they cannot be separated by applying much force. This is due to the pressure difference across the walls of the hemispheres. When the hemispheres are vented, the created pressure difference vanishes and the hemispheres can easily be pulled apart.


14Small amount of shaving foam in a glass cup is placed in a bell jar, when the vacuum inside the bell jar is turned on many pockets of air trapped inside the shaving foam expand in a vacuum enviornment. As the pressure gradually decreases the volume of the shaving foam gets bigger and bigger. If the created vacuum is reversed, the volume of the shaving foam gets smaller and smaller accordingly.


15This is a simple model of vacuum elevator operation. In this model, there is a vertical glass tube, one end of which is connected to the evacuation port while other is at atmospheric pressure. There is small sample of glass elevator duly sealed at its both ends with two rubber O-rings. When evacuation valve is opened, the elevator goes up due to pressure difference, conversely when evacuation valve is closed it comes down due to gravitational force.


16In this demonstration, there are two glass pipes A and B. Pipe A is at atmospheric pressure while pipe B is evacuated. Firstly, when a metallic ball and a bird feather is dropped into pipe A, metallic ball reach the bottom of pipe earlier than lighter bird feather later due to air resistance. On the other hand, when these two items are dropped into evacuated pipe B, they both fall simultaneously as there is no air in this pipe and there is no resistance to the lighter bird feather.


17In this glass setup, a glow discharge is formed by passing electric current through air at low-pressure. Basically it is created by applying a high voltage between two metal electrodes in a glass tube containing low air pressure. When the voltage exceeds a certain limit called the striking voltage, the air in the tube is being ionized and begins conducting electricity, causing it to glow with a colored light. The color depends on the air or gas used, applied voltage and vacuum range in the tube.


18This mercury barometer has a glass tube, closed at one end, filled with mercury and its open end inverted in another mercury-filled reservoir at the base. Atmospheric pressure exerts force on the surface of mercury in the reservoir, forcing certain mercury column height in the glass tube. Low pressure or vacuum on the surface of mercury in the reservoir allows the mercury column height in the glass tube to drop to a lower level.


19In this experiment, vacuum filtration technique is used for separating a solid product from a solvent or liquid reaction mixture. The mixture of solid and liquid is poured through a filter paper in a Buchner funnel. The solid is trapped by the filter and the liquid is drawn through the funnel into the flask below. At atmospheric pressure, this process takes more time while under vacuum it speeds up.


20This interesting apparatus is designed to show the playing of vacuum water fountain. It is formerly evacuated through the evacuation port and then built in valve is closed. Afterwards, its lower part is placed in glass water pan and built in valve is opened. The pressure difference across the water in the pan causes the water to enter the evacuated glass volume and hence from the water fountain.