Does the required time to heat a body from 20°C to 40°C the same as from 40°C to 60°C?
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The energy required to heat something is the temperature difference multiplied by the mass multiplied by the thermal capacity.
Thermal capacity is technically temperature dependent, so heating a 40°C object by 1K takes a different amount of energy than heating that same object by 1K at 0°C, but for most materials and normal temperature ranges it’s fairly accurate to just assume a constant thermal capacity.
So the **energy** required to do the heating is (more or less) the same in either case.
The **time** depends on how the thing is being heated. If you have a constant power source that’s heating the body, and we neglect any losses, then yes, both heating phases would take the same amount of time.
If you instead are heating the object using something at a constant temperature (so for example placing it inside a 100°C hot room), then the power absorbed by the object is higher when it’s cold, since thermal power transfer is proportional to temperature difference, so a 40°C object in a 100°C room will heat to 41°C faster than that same object will heat from 60°C to 61°C, so in that case the second heating portion would take longer than the first.
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