What causes a vacuum?
 Fred |
 Lilly |
„
Last summer I helped my grandma cooking jam. First of all the hot jam was filled in hot jars. Afterwards she screwed the lid on it covering it airtight. When the jam had been cooled down the lids were very tight.
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„
The lid sits that tight because of the vacuum sucking on the lid.
So when I open a jar it snaps because suddenly air is flowing into the vacuum.
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„
Your idea with the vacuum is just great. But I´m not sure if a vacuum can suck on something at all. But what happens anyway when a hot jar cools down?
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