Register to reply

Hot water feels cold

by daniel_i_l
Tags: cold, feels, water
Share this thread:
daniel_i_l
#1
Sep12-07, 09:12 AM
PF Gold
daniel_i_l's Avatar
P: 867
If you suddenly put your hand into very hot water it feels cold (or atleast, it's hard to tell if it's hot or cold) for the first second.
Why is this so?
Thanks.
Phys.Org News Partner Physics news on Phys.org
How did evolution optimize circadian clocks?
New webcast series brings cutting-edge physics talks to the world
High Flux Isotope Reactor named Nuclear Historic Landmark
Morga
#2
Sep12-07, 10:09 AM
P: 27
I guess it's because of two things: Firstly the transfer of energy from the "hot" particles in the water to your hand. Tempreture is a measure of kinetic energy of particles. A hotter tempreture means a greater velocity of the particles. For heat to be transferred the kinetic energy must be transferred to your hand for collisions, also heat needs to be transferred through yourbody tissue which has a poor thermal conductance. Although there were be a slight lag between your hand heating up from the water it would be very slight. I pressume much of the time difference is due to impulses traveling to and from the brain to tell your body that the water is hot.
Kurdt
#3
Sep12-07, 10:23 AM
Emeritus
Sci Advisor
PF Gold
P: 4,980
This would be better in a biology forum I suspect. I read or heard somewhere a few years back that its hard for your nervous system to tell the difference between very hot and very cold objects. Thats why it sometimes feels like you've been burned when you touch something very cold, and why you think hot water is cold when you first put your hand under it. Unfortunately I don't know any of the details, hence a move to a biology forum might be best.

lanman
#4
Sep12-07, 08:23 PM
P: 8
Hot water feels cold

Google "the cold/hot grille illusion." It is an interesting tactile hallucination. I think there's a wikipedia on it.
DaveC426913
#5
Sep12-07, 09:32 PM
DaveC426913's Avatar
P: 15,319
Yes, it has something to do with the fact that both nerves are stimulated, but one of them travels slightly faster and reaches the brain milliseconds sooner.


Register to reply

Related Discussions
Hot water can cool faster than cold Chemistry 7
Why does hot water visually separate from cold? Classical Physics 3
Hot wax and cold water. Chemistry 8
Cheap soap and cold water General Discussion 9
Water evaporating from my hand in the cold. General Physics 6