Question

Four containers are filled with warm water and are allowed to cool on the kitchen counter. Heat losses due to conduction through the bottom and due to natural convection are negligible. Which container cools the fastest?

A. shiny metal
B. dull metal
C. dull black
D. shiny black
E. they all cool at the same rate

Answer 1

The dull black container cools the fastest because its high emissivity allows it to radiate heat more efficiently.

When it comes to cooling, the dull black container will cool the fastest. This is because dull black surfaces have a higher emissivity, which means they can radiate heat more efficiently than other surfaces. Shiny surfaces, on the other hand, have a lower emissivity and reflect more heat back into the container, slowing down the cooling process.

In addition to radiation, the rate at which an object cools also depends on other factors such as surface area and temperature difference. However, since the question states that heat losses due to conduction and convection are negligible, the main factor affecting the cooling rate is radiation.

Therefore, the dull black container will lose heat the quickest, making it the fastest to cool.