If I put something in the fridge that’s 30°C, does it get colder faster than something I put in at 15°C, over a 20 minute period?

Question

If I put something in the fridge that’s 30°C, does it get colder faster than something I put in at 15°C, over a 20 minute period?

In: Physics

Answer 1

It depends on what you mean by “get colder faster.”

Heat transfer rates are a function of a difference in temperature, but this rate is at a given moment in time. Thus, as the items approach each other in temperature, the actual rate of heat transfer decreases, and thus the rate of change of temperature also decreases.

So, strictly speaking, the item in the fridge at 30C will lose heat more rapidly than the item at 15C at first, but if your end goal is to reach a certain *particular* temperature (e.g. 5C), the object at 15C will still get there first.