air pressure

Experiment Two Two weeks after the first one, another experiment. And my first thought is: isn’t this a bit dangerous? Hot water in cans that buckle and cave in? The teacher’s really got to be 100% sure his grasp of Physics is up to par, or we could be looking at a class full of maimed kids. Not that anyone would have really cared about that back then. But I’d have a hard time believing you could do this experiment with a bunch of eight year olds in 2021. Again, I’m not sure I’ve written this up in the most effective manner. Yes, I’ve described what happened, but I don’t think I quite grasped why. I mean, if the top’s on, the steam can’t escape, so surely the pressure of the steam - which wants to escape the bottle - must make it explode outwards, not buckle and implode? Got to find a way of explaining it. Maybe using another experiment on the internet will help. OK, here’s one: https://coolscienceexperimentshq.com/how-to-crush-a-bottle/ - This one uses a plastic bottle and, crucially, needs to be lying in a bed of ice, with cold water poured onto it. I expect we managed to skip this part because we were in Yorkshire in the middle of November (so it was already icy enough), but it’s entirely possible I just forgot to mention it. The way it works, apparently, is that cool air exerts less pressure than warm air. The air in the bottle is room temperature until hot water is added, which heats the air. But when the air cools, the pressure decreases, and if there’s nowhere for the hot air to go, the pressure of the air outside the bottle is greater than the pressure of the air inside, and the bottle caves in. For some reason… No, I still don’t understand it… Can you explain it to me? Please write to waen@waenshepherd.com and tell me how it works. I’ll write up the best answers here so everyone can see them. So definitely don’t write me silly answers.

Thursday November 8th, 1979

Air Pressure

< Water Pressure

Water Pressure Air Pressure Air Air Pressure (revisited)

FAIRBURN The place where I wrote all this rubbish

WAEN SHEPHERD Who was this strange little boy?

GEOGRAPHY 1 Sept 1979 - Feb 1981

HISTORY 1 Sept 1979 - Oct 1981

The Forgotten World John and Mick fall foul of some extreme potholing

Christmas 1979 Can Waen last the night without opening his presents?

Great Space Battles Three mighty empires take their first steps into outer space

TERM 1 A day-by-day account of Waen’s first term at Fairburn School

TERM 2 The birth of the 1980s - Blake’s 7, Blondie and battles in space

TOPIC 1 He knows the names of all the dinosaurs

TOPIC 2 The one where it all kicks off

Waen Shepherd 2 Waen’s heroic antics in the far-flung future of 2007 AD!

Air >

Experiment Two Two weeks after the first one, another experiment. And my first thought is: isn’t this a bit dangerous? Hot water in cans that buckle and cave in? The teacher’s really got to be 100% sure his grasp of Physics is up to par, or we could be looking at a class full of maimed kids. Not that anyone would have really cared about that back then. But I’d have a hard time believing you could do this experiment with a bunch of eight year olds in 2021. Again, I’m not sure I’ve written this up in the most effective manner. Yes, I’ve described what happened, but I don’t think I quite grasped why. I mean, if the top’s on, the steam can’t escape, so surely the pressure of the steam - which wants to escape the bottle - must make it explode outwards, not buckle and implode? Got to find a way of explaining it. Maybe using another experiment on the internet will help. OK, here’s one: https://coolscienceexperimentshq.com/how-to- crush-a-bottle/ - This one uses a plastic bottle and, crucially, needs to be lying in a bed of ice, with cold water poured onto it. I expect we managed to skip this part because we were in Yorkshire in the middle of November (so it was already icy enough), but it’s entirely possible I just forgot to mention it. The way it works, apparently, is that cool air exerts less pressure than warm air. The air in the bottle is room temperature until hot water is added, which heats the air. But when the air cools, the pressure decreases, and if there’s nowhere for the hot air to go, the pressure of the air outside the bottle is greater than the pressure of the air inside, and the bottle caves in. For some reason… No, I still don’t understand it… Can you explain it to me? Please write to waen@waenshepherd.com and tell me how it works. I’ll write up the best answers here so everyone can see them. So definitely don’t write me silly answers.

Thursday November 8th, 1979

< Water Pressure