Question No.  19967 :
1) Boyle's Law state that the product of pressure and volume in a system is a constant if the temperature is unchanged, i.e. as pressure increases, volume would decrease. How is it that as air is pumped into a balloon, both the volume and the pressure increase, even when temperature remains unchanged. How is Boyle's law obeyed?
2) There is an experiment where a cardboard is placed above a cup partially filled with water. Upon inverting that cup with the cardboard covering the mouth of the cup, the cardboard remains at the mouth without external support, keeping the water inside the cup. There is a need for a minimum amount of water for this experiment to be successful. What are the factors that affect this experiment?

1) In the mid 1600's, Robert Boyle studied the relationship between the pressure p and the volume V of a confined gas held at a constant temperature. Boyle observed that the product of the pressure and volume are observed to be nearly constant, that is pV = constant Hence, Boyle's Law states that the product of pressure and volume in a closed system is a constant if the temperature is unchanged for a fixed mass of gas. Since more and more air is pumped into the balloon to inflate it, the situation will not obey Boyle's Law, as the mass of gas in the balloon is not fixed. 2) This experiment is most successful if you use a hard plastic container and fill it to the brim with water such that there is no air space between the water surface and the cardboard when you cover the mouth of the container with it. If the cardboard is a bit wet on the suface, it will make a better seal around the mouth of the container so that air cannot get into it. When the container is inverted with the cardboard covering its mouth, the cardboard remains at the mouth without external support. Any water flowing out of the container will cause a pressure difference inside and outside the container resulting in a force pushing the cardboard upwards to seal the mouth of the container. If there is too much air in the container, the pressure difference might not be big enough and the resulting upwards force on the cardboard might not be large enough to support the weight of the water in the container and the experiment will not work. Another factor is the area of the mouth of the container must be large enough so that the force provided by the difference in pressure ( force = pressure x area) is sufficient to support the weight of the liquid above the cardboard. Question Asked By:

Name: Yap

Age Group: 21 to 30

Occupation Type: Educationalist

Education Level: Graduate