Science Buddies: "Ask an Expert"

you wake up in the middle of the night craving a cold glass of milk. you sneak down to the fridge and open the door. still partially asleep, you stare at the contents of the fridge until you notice that your bare feet are getting uncomfortable. are they hot or cold? explain.

Ahmedmajali,

Science buddies are here to guide you to finding the answers yourself rather than to just give them away. I'm sure that you can come up with a simple experiment to answer your question. For starters, I would go down to the kitchen and stand in front of the fridge until your feet are uncomfortable and measure how long this takes. Then try touching your feet. How do they feel? This could be followed up by a more in depth experiment which will help you further understand temperature changes. This field of science is called thermodynamics and can be very interesting but rather complicated. An experiment found in our project ides that might help you to understand what is happening is "what is the fastest way to cool a soda." The link is https://www.sciencebuddies.org/science- ... p057.shtml. I hope this helps.

I tried the experiment (without waking up in the middle of the night). I felt my feet get cold, I thought because the cold air is at the bottom hit my feet, they got colder. Does that sound right?

You are on the right track. Cold air is heavier than warm air and as a result your feet get cold before the rest of you. An easier way to see is to fill two clear glasses with water. One glass filled with warm or hot water and the other with cold water. Add food coloring to one of the glasses and then pour the cold water into the warm. You will see the cold water sink and then distribute through the rest of the water as it comes to an equilibrium. There are four types of energy exchanges which can occur. These are conduction, convection, evaporation and radiation. The water experiment and your feet experiment are actually two different kinds of energy / heat exchange. This maybe something for you to explore more in depth. What is your actual science project?

ahmedmajali,

In addition to the cold air playing a role in the transfer of heat, I would also suggest thinking about the temperature of the floor. A tile floor, for instance would feel much colder than would a carpeted floor. Remember that what you are feeling as hot or cold is related to the transfer of heat, as Gizzmo 46 has pointed out.