Gas Law Experiments Corinne McKenna-8th Grade Marshmallow in a Vacuum Balloon in Liquid Nitrogen Candle Under a Glass

Marshmallow in a Vacuum In this experiment we place a marshmallow under a bell jar and reduce the amount of pressure being experienced in the jar. The marshmallow experiment is an example of Boyle’s Law. To review, Boyle’s Law is, P1V1=P2V2. The equation demonstrates that as pressure increases, volume decreases OR when pressure decreases, volume increases. It is also important to remember that temperature is at a constant for Boyle’s Law. The marshmallow experiment works with Boyle’s Law because as we decrease the pressure in the bell jar, the volume of the air within the marshmallow increases. We also see the other side of Boyle’s Law when returning the pressure into the bell jar and putting the marshmallow back into the normal environment. When the pressure is returned back to normal, the marshmallow shrinks and becomes shriveled because of the weight of the pressure pushing on the marshmallow. Watch the following video to see the marshmallow video in action: http://www.youtube.com/watch?v=cIVMkVSIAbw&feature=endscreen

Candle Under a Glass with Water In this experiment we place a lit candle in the middle of a bowl that contains water. Then we place a glass over the candle to cause it to be extinguished. When the candle goes out, the water moves from the outside of the glass to inside the glass. This experiment is demonstrating Gay-Lussac’s Law. To review, Gay-Lussac’s Law is P1/T1=P2/T2, which shows that as pressure goes up, temperature goes up as well, and when pressure goes down, temperature goes down. Gay-Lussac’s Law is seen in the candle experiment because as the temperature goes down inside the glass, which is shown by the candle going out, the pressure decreases as well. We know that the pressure decreases inside the glass because the water from the outside is pushed inside the glass. This event occurring means that the pressure outside of the glass is higher than the inside and the air pressure from the outside is pushing the water into the area of lower air pressure. If the water did not move from the high to the low area of air pressure, then we would assume that the pressure was in equilibrium. Watch the following video to see how the candle experiment works: http://www.youtube.com/watch?v=zSL6RT1DEHI

Balloon in Liquid Nitrogen In the balloon in liquid nitrogen experiment we simply place a balloon filled with air into a container filled with liquid nitrogen. When the balloon is placed in the liquid nitrogen bath, the balloon begins to shrink and when the balloon is taken out of the liquid nitrogen, the balloon slowly re-inflates to its full size. This experiment demonstrates Charles’ Law. As you remember, Charles’ Law is V1/T1=V2/T2, which states that when volume increases, temperature increases and when volume decreases, temperature decreases. Both aspects of Charles’ Law is evident in the balloon in liquid nitrogen experiment. When the balloon is placed in the liquid nitrogen the temperature decreases greatly, so the balloon loses volume and shrinks. The reverse effect is seen when the balloon is taken out of the liquid nitrogen bath. The temperature is increased so the volume of the balloon increases as well. Watch the following video to get a visual of the liquid nitrogen experiment: http://www.youtube.com/watch?v=sEbxLrP_ZCU

Citation Slide Slide 1: Marshmallow Image http://brainchildblog.com/wait-dont-eat-that-marshmallow/ Slide 1: Candle Image://www.oldschool.com.sg/index.php/module/PublicAccess/action/Wrapper/sid/ea5f3768e0dae62aa6d01beee8123931/cmbn_id/923/qba/1 Slide 1: Balloon Image http://physics.appstate.edu/catalog/thermodynamics/gas-law/constant-pressure/balloons-liquid-nitrogen Slide 2: (marshmallows): http://mrwiggersci.com/chemold/lab_demo_pics/demo_pics/boyles_law/boyle-law.htm Slide 3: (candle graphic) http://www.daviddarling.info/encyclopedia/C/combustion.html Slide 4 (balloon graphic): http://www.nhn.ou.edu/~see/thermo/thermo.html