A hot pan sits on a switched-off burner. Nobody touches it. Minute after minute, it cools toward room temperature.
Nothing outside keeps the cooling going. Some changes work like that, and some do not. Which is which?
The pan's cooling keeps going on its own. Nothing outside has to keep driving it along.
Now consider the same pan over a lit burner. It stays hot only while the burner supplies energy.
When the burner is switched off, the staying-hot ends. The cooling then starts, and the cooling needs no driver at all.
Here is the test. Once a change is underway, ask: does the change carry on when everything outside is switched off or taken away?
A pool float holds air, and its valve is opened. The air leaks out on its own. No device runs while it leaks.
A pump inflating the same float is the other kind. If the pump stops, the inflating stops.
A spoonful of sugar rests at the bottom of a glass of still water. The sugar dissolves through the water on its own, with nothing driving it.
A camping lantern stays lit through the evening. Does the staying-lit keep going on its own, or stop unless something outside keeps driving it?
If the batteries are removed, the light dies at once.
The staying-lit lasts only while the batteries supply energy.
The staying-lit stops unless something outside keeps driving it.
An inflatable tube man dances beside a shop while a blower runs. Does the dancing keep going on its own, or stop unless something outside keeps driving it?
If the blower is switched off, the tube man sags and the dancing ends.
The dancing lasts only while the blower drives air through it from outside.
The dancing stops unless something outside keeps driving it.
A scoop of drink mix rests at the bottom of a pitcher of still water and dissolves through it. Once underway, does it keep going on its own, or stop unless something outside keeps driving it?
An unplugged waffle iron cools on a kitchen counter. Once underway, does it keep going on its own, or stop unless something outside keeps driving it?
A ceiling fan spins at a steady rate. Once underway, does it keep going on its own, or stop unless something outside keeps driving it?
An aquarium bubbler streams bubbles up through a fish tank. Once underway, does it keep going on its own, or stop unless something outside keeps driving it?
An air mattress with its valve open slowly goes flat. Once underway, does it keep going on its own, or stop unless something outside keeps driving it?
A phone's battery charges from 20% to 80%. Once underway, does it keep going on its own, or stop unless something outside keeps driving it?
Which process keeps going on its own once underway?
A lawn sprinkler sprays while a faucet feeds it. Which check settles whether the spraying keeps going on its own?
In the morning, an electric pump inflates a kiddie pool. In the evening, the valve is opened and air leaks back out. Once underway, which of the two processes keeps going on its own?