Wat substance cannot be separated physically or chemically?

Anything that cannot be separated physically or chemically is an element.

because u need two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei to form isotopes.

so since they all have the same shape? i mean maybe because m& m and reeses are both chocolates

o conteúdo de calor de um sistema é igual à entalpia apenas para um sistema que é constante