what does mean that diamond is thermodynimecally stable where asَ coal is not so ?

Answer 1

When you burn coal, it changes, chemically.
Not so with a Diamond.

Answer 2

Thermodynamic stability
Diamonds will burn at approximately 800 degrees Celsius, providing that enough oxygen is available. This was shown in the late 18th century, and previously described during Roman times. There are several allotropes of carbon, graphite and diamond are the most well-known. The diamond allotrope is metastable with respect to the graphitic phase under normal conditions; that is, graphite is thermodynamically favored over diamond (ΔG = −2.99 kJ / mol). However, the rate of conversion from diamond to graphite is extremely slow due to the presence of a large kinetic barrier to this rearrangement. It would take an extremely long time (possibly more than the age of the Universe) for an appreciable amount of diamond to decay into graphite.


Or in english.... Diamonds require extreme amounts of heat to change. Coal does not.

Thermo- means heat
Dynamic- change

Answer 3

What all the previous answers explained is that diamond is DYNAMICALLY more stable.
That is it requires a lot more energy to turn diamond into CO2 then coal.
THERMODYNAMIC stability means that a substance is lower in energy (more stable) then its reaction products. Specifically diamond is lower in energy then the equivalent amount of CO2, where as coal is higher in energy then CO2.

Answer 4

I'm guessing it means that diamond is not --at least, not very -- combustible, whereas coal is highly combustible (i.e. diamond will not burn). Not positive about that, as I've never attempted to burn a diamond, but it seems the most likely explanation to me.

That was also assuming you meant "thermodynamically."

Answer 5

Coal can burn, a diamond can not.

Answer 6

means that coal burns

diamonds dont burn nearly as easilly