Ice melts in a warm room. No device runs, nobody stirs, and the melting carries on anyway.
Changes of this kind come up constantly in physics. They have earned a name of their own.
Ice melting in a warm room proceeds on its own once underway. No device has to drive it.
The melting ice is a spontaneous process.
An electric kettle's water stays at a rolling boil only while the element runs. The boiling is not spontaneous, because the element is continuous outside help.
The word says only this: once underway, the process needs no continuous outside help.
Help at the start does not spoil it. A process someone starts can still be spontaneous, if it then proceeds on its own.
So the sorting you practiced is the test for the name: a change that keeps going on its own is spontaneous, and a driven change is not.
Fizz bubbles rise and escape from a just-opened bottle of soda. Is the fizzing spontaneous?
Once the cap is off, the fizzing proceeds with no continuous outside help.
Opening the cap started things, but help at the start does not spoil it.
Yes. The fizzing is spontaneous.
An electric blanket keeps a bed at 35 °C through a cold night. Is the staying-warm spontaneous?
The blanket's element supplies energy the whole night.
That supply is continuous outside help.
No. The staying-warm is not spontaneous.
A party balloon slowly sinks over a few days as helium leaks out through the balloon's skin. Is the leaking spontaneous?
Keane says: 'A puddle drying up through a dry afternoon is a spontaneous process.' Is he correct?
Which of these processes is spontaneous?
A fish tank stays at 26 °C in a 20 °C room while its heater runs. The staying-warm is not a spontaneous process. What rules it out?
Which of these processes is spontaneous?
A process proceeds on its own once underway, with no continuous outside help. What is such a process called?