Where Does the Energy Come From in Capillary Action?

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Discussion Overview

The discussion centers on the source of energy involved in capillary action, particularly in the context of water being absorbed by a paper towel. Participants explore the relationship between intermolecular forces, gravitational potential energy, and the energy required for the process, including hypothetical scenarios such as the absence of gravity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions where the energy comes from to lift water molecules in capillary action, noting that their gravitational potential energy increases.
  • Another participant suggests that the energy required comes from the energy used to manufacture the paper towel.
  • A participant introduces a hypothetical scenario where gravity is removed, indicating that the answer to energy sources in capillary action becomes more complex in that context.
  • Concerns are raised about whether intermolecular forces are 'used up' as they contribute to lifting water molecules, with a participant asserting that only energy is consumed, not the forces themselves.
  • It is proposed that capillary rise converts surface energy into gravitational potential energy, with a balance achieved when the liquid stops rising.

Areas of Agreement / Disagreement

Participants express differing views on the source of energy in capillary action, with no consensus reached on whether intermolecular forces are consumed or merely transformed into potential energy.

Contextual Notes

Some assumptions regarding the definitions of energy and forces in this context remain unaddressed, and the implications of removing gravity introduce additional complexity that is not fully explored.

tony873004
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If you dip a paper towel into water, the water absorbs up the paper towel. These molecules are gaining height, and hence mgh is increasing. Where does the energy come from to lift the water molecules?
 
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From the energy required to manufacture the paper.
 
Here's a twist- what happens if you take away gravity? The answer is not so simple, and relates to how to grow food in space.
 
So, if the energy required to lift the water through capillary action, is coming from the
inter-molecular forces, then why aren't these forces being 'used up' very slightly as they convert their energy into the gaining of height by the water molecules?
 
The forces aren't 'used up'. Onlly energy is used up. you can get energy out of water and a paper towel by letting the towel get wet. you have to spend energy to get the water out of the towel again. (pressing or heating)
 
Pyro Ninja said:
So, if the energy required to lift the water through capillary action, is coming from the
inter-molecular forces, then why aren't these forces being 'used up' very slightly as they convert their energy into the gaining of height by the water molecules?

Capillary rise coverts surface energy into gravitational potential energy. When the liquid stops rising, the increase in potential energy is balanced by the loss of surface energy from wetting.
 

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