A spontaneous process is one that occurs naturally and without the need for external intervention, under appropriate conditions. In other words, we can say it happens on its own under specific circumstances.
While a nonspontaneous process does not occur naturally and requires some external influence or energy to take place.
Four examples of both processes are:
Spontaneous processes:
- Water flowing downhill: When water flows from a higher place to a lower place, like a river running downhill, it naturally happens due to gravity, without needing extra energy.
- Ice melting at room temperature: Ice will naturally melt into water above 0°C. It doesn’t need anything extra to make this happen.
- A rock rolling down a hill: If a rock is placed at the hilltop, it will naturally roll down due to gravity, without needing any external force to make it move.
- Rusting of iron: When iron is exposed to air and moisture, it will slowly rust (form iron oxide) over time. This is a spontaneous process that occurs naturally.
Non-spontaneous processes:
- Water flowing uphill: For water to flow uphill, we need to pump it or apply energy (like in a fountain). Water doesn’t flow uphill by itself.
- Freezing of water at room temperature: Water will only freeze into ice if we put that below 0°C. At room temperature, this does not happen naturally, and energy must be removed from the water to make it freeze.
- Unmixing of a solution: If we mix sugar in water, the sugar dissolves. For the sugar to separate back out on its own, energy would need to be added, such as by evaporating the water.
- Charging a battery: A battery cannot charge itself. We need to connect it to an external power source to add energy and recharge it.