3 Perplexing Physics Problems

everyone knows if you shake up a carbonated drink it explodes but why is this well here I have an identical bottle with a pressure gauge fitted to it and I want you to make a prediction right here if I shake up this bottle will the pressure increase decrease or remain the same and while you're thinking about that let me tell you this video is sponsored by Squarespace the all-in-one platform for building your online presence more about Squarespace at the end of the show okay I hope you've made your prediction and registered it in the poll up here this bottle has been sitting stationary for a few days at room temperature you can see the pressure reading is about three atmospheres 330 kiloPascals and I'm going to shake it up and see what happens ready in three two one and the pressure is still the same you might suspect that well maybe this bottle is all out of gas maybe it wouldn't explode on me so just to make sure yep it would go so it's not an increase in pressure that causes a bottle to explode like that so why is it we shouldn't feel bad if you predicted that the pressure would increase because in fact that explanation was published in New Scientist in 1986 leaving many other scientists to come forward saying that is not the real explanation so we will find out what it is after we explore the second perplexing physics problem consider this if you put identical ice cubes in a cup of fresh water and a cup of saltwater which ice cube will melt first again you can register your prediction by answering the poll here now as you're thinking about that I want to show you the setup okay so here I have regular fresh water I'm just gonna fill up each cup then I'm gonna add about a tablespoon of salt into this cup on the right if you know a bit about chemistry you may recognize that adding sodium chloride water actually takes energy and so it lowers the temperature of this solution by a little bit so I've got a thermometer just to check and I'm gonna let this solution sit here for a while so that it comes back up to room temperature okay have you made your prediction let's put these ice cubes ...