Basically the title: but what about a substance makes it makes it’s specific heat capacity higher or lower than another? From what I understand, SHC is the amount of energy absorbed by a substance in order for it to be raised by 1C. But on a molecular level, what determines this and why is it different between different substances or different states of a substance? eg liquid water has SHC of 4.184J/JC, ice has SPC of 2.11J/JC and vapour has SPC of 2J/JC. Very convoluted question but an explanation would be greatly appreciated 🙂
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One of the biggest factors is the mass of the atoms involved. The lower the atomic mass, the higher the specific heat in inverse proportion. This relationship holds accurately between molecules made of just single atoms, like helium, neon, argon, etc. The relationship also works fairly well amongst metals. For other molecules the structure itself plays a role but, still, two of the compounds with very high specific heats, ammonia (NH3) and water (H2O), are considerably helped by all those very-light hydrogen atoms. On the other hand, uranium, with a very high atomic mass, has an extremely low specific heat.
Fundamentally it comes down to the fact that temperature is a measure of the average energy of the particles (the atoms and molecules). The kinetic energy of a moving particle is proportional to its mass multiplied by the square of its velocity. A particle that is 4 times lighter needs to move 2 times faster to have the same energy.
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