Final answer:
To calculate energy change on 'diagonal' sections of a heating/cooling curve, use Q = mcΔT for temperature changes, and Q = mL for phase changes, where m is mass, c is specific heat capacity, ΔT is temperature change, and L is latent heat.
Step-by-step explanation:
To calculate the energy change on the "diagonal" sections of a heating/cooling curve, the formula used depends on whether the substance is undergoing a phase change or a change in temperature. For sections where the substance is not changing phase (i.e., purely increasing or decreasing in temperature), the formula is Q = mcΔT, where Q is the heat energy, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature. During phase changes, however, the energy is calculated using Q = mL, where L is the latent heat of the phase change. The latent heat will be either the latent heat of fusion (for melting or freezing) or the latent heat of vaporization (for boiling or condensing).
The concept of energy and phase changes is fundamental in thermodynamics, which is an important aspect of chemistry and physics. Recognizing that the energy required should scale with the mass of the substance and the temperature increase/decrease or phase change is crucial for a deeper understanding of the heating and cooling processes.