Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Cooling Curve Experiment
Name: Russell
Status: student
Grade: 9-12
Location: LA
Country: N/A
Date: 1/3/2006


Question:
I am doing a Science project on the classic, which color absorbs more heat. I am using 2 sets of white and black jars, each white jar with a corresponding black jar of the same size, and vice versa, but to spice things up and stray a little from what everyone else is doing, I also want to find which color --cools-- faster. I have attempted to fill the jars with hot water and then record the temperature every minute but they appear to cool at almost exactly the same rate. I think this is because there are far too many other factors affecting the cooling rate and the color is not the main variable. Do you have any ideas on how to isolate the color factor so I can test my hypothesis and determine which one will cool faster?


Replies:
To do this experiment you would want to perform the experiment in the dark so no radiation would be adding to the heat content. It should also be performed in vacuum so that convective cooling cannot occur.

Having said that, let me at that at the temperatures you can achieve in this experiment I would not expect to see much difference. The energy that is emitted is mostly in the infrared and the visible colors you see will not be indicative of what is happening in the infrared. You could try to characterize your materials for heating in the infrared by using an infrared light source instead of the sun. It would be interesting to see if you are able to detect any difference in the heating with an infrared light source.

Greg Bradburn


Hi Russel

Be sure your jars are in the same environment; that is, the same ambient temperature, the same light, same elevation, same air movement, etc. Also be sure they are far enough away or insulated from each other so jars will not interact with each other. Color alone may not be a factor here. Emissivity in the visible light range is different than in the IR range and is dependent on the coating all white coatings are not created equally. You may be seeing a dT/dt that could take some very sensitive instrumentation to resolve. You may want to try flat black and a metallic paint it might give you more of a spread you can measure. Hope this helps.

Robert Froehlich


The rate of cooling is dominated by two factors that are independent of color. The first factor is the temperature difference between the temperature of the jar and the surroundings, which depends only on the temperature difference and not the other factors in the experiment such as the "color" of the bottle etc. The second is convection of air around the bottles over which you have little control without more carefully designed conditions. In addition, heat input depends upon the infrared radiation impinging on the bottle samples -- again something that is difficult to control simply. I fear that the color factor is going to be swamped by these other larger variables. One point that somehow gets "missed" in the teaching of absorption of heat/radiation is that "color", except under very carefully controlled conditions plays a minor roll in the overall effect. "Color" is such a minor factor in the forest of factors affecting cooling rate, it is futile to attempt to observe differences and reliably ascribe the differences to the "color" of the object. Your instinct that "there are far too many other factors affecting the cooling rate..." is right on target and very succinctly stated.

Vince Calder



Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory