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Thermal dissociation involves breaking chemical bonds through the application of heat. Both $CuCl_2$ and $CaCO_3$ can thermally dissociate:
$CuCl_2(s) rightarrow Cu^{2+}(g) + 2Cl^- (g)$
$CaCO_3(s) rightarrow CaO(s) + CO_2(g)$