Scientists have concluded that the uppermost part of the mantle is partially-molten. Which observation helped them reach this conclusion? Both P and S waves slow down when they reach this layer.

Both P and S waves speed up when they reach this layer.

P waves do not travel through this layer.

S waves do not travel through this layer.

practical process described pest part of scientific investigation.

because practical knowledge is powerful then therotical knowledge.

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.