# Lower energy level more stable why?

1. Oct 26, 2013

### Vivek des

I am a high school student.. I have come across so many times that lower energy state of matter is more stable than higher energy states .. I cant understand why. Someone help me out.. Thanks.

2. Oct 26, 2013

### hilbert2

It's not that simple. The thermodynamic stability of a state of matter, relative to some other state, depends not only on the difference in "energy" between the states, but also on the difference in the entropy of the states. The relative importance of these considerations depends on temperature. In higher temperature the higher energy state can be more stable.

Also, even a thermodynamically unstable state can be kinetically stable, which means that the transformation to other states is so slow that it can't be observed.

3. Oct 26, 2013

### Vivek des

I do have some idea on thermodynamics can u explain further?

4. Oct 26, 2013

### hilbert2

For example, at room temperature calcium oxide and carbon dioxide react to form calcium carbonate: $CaO + CO_{2}\longrightarrow CaCO_{3}$. The product is lower in energy than the reactants, and therefore energy is released to the surroundings in the reaction. However, at a high temperature the combination of $CaO$ and $CO_ {2}$ is more stable than $CaCO_{3}$. Therefore, when calcium carbonate is heated strongly, the opposite reaction happens: $CaCO_{3}\longrightarrow CaO + CO_{2}$. This happens because the $CaO$ and $CO_ {2}$ are higher in entropy than $CaCO_{3}$.

Investigating the stability of states of matter, using concepts like Gibbs free energy, is not high school level material, but you will encounter it if you go on to study chemistry and physics in university.

5. Oct 26, 2013

### HallsofIvy

Staff Emeritus
"Force" is the negative of the gradient of the potential energy function. That is, the gradient points in the direction of increasing energy so the force vector point in the direction of decreasing energy. If we move away from a position of lowest energy, the resultant force pushes us back.

6. Oct 26, 2013

### dauto

It's very simple. A state can spontaneously shed excess energy and convert to a lower energy state. The reverse cannot be done spontaneously because it requires an external source of energy to supply the needed energy excess.