If I keep a plastic mineral-water bottle topped up with tap water and regularly drink directly from it, the neck smells vile after a couple of weeks. Why is this and why is it always exactly the same smell?

In order to open polythene bags and those A4 plastic paper sleeves you need to wet your fingers, but too wet or completely dry and your fingers can't get a grip.

In my parent's house, we used to store some plastic salad boxes in a wooden cupboard in the cellar. Before storage theses boxes have been emptied, washed and stacked into one another. After some time, at least half a year of longer, we found some of these boxes glued together, where their walls touched each other. To me it looks like there was a chemical reaction going on. Can somebody please explain to me what exactly is going on there?

We have a toaster with a plastic lid. One is supposed to put the lid on only after the toaster has cooled off, to protect the inside of the toaster from dust. But apparently some time ago someone neglected the pictogram and put the lid on while the toaster was still rather hot. Now in the most heat-exposed places, the plastic has become of a clearer transparent color, more irregular shape of surface, and there are a lot of fine bubbles inside, about half a millimeter in diameter. My question is: What is in the bubbles and how did it get there? Did the plastic contain fine dispersed air initially? Or maybe water or some organic components that "boil" at a moderate temperature?