A little help with a lab writeup?

ID:185303
 
Mar 7 2006, 8:09 pm
In one of our recent labs for Earth Science, we tested to see which would heat up faster- a "rough" black painted can, or a metallic silver can. Obviously, the results showed the black painted can heated up faster. However, they also showed the black can cooled down faster. One of the questions on the writeup is why that happened. I understand it heating up faster, because dark colors absorb more, and rough surfaces do as well (the light 'bounces around' on the surface, whereas on a smooth surface it 'hits' once and is reflected off), but since they were both made of the same metal can, they should have the same specific heat and cool down at the same rate, right? At least, that's my understanding of it. Could someone help me out?

Thanks a lot!
Mar 7 2006, 9:53 pm
I'm not entirely sure why, but it's definitely the right observation. It's good to see someone being so observant in science.

Try looking up information on 'blackbody radiation'.
Mar 8 2006, 4:13 am
Airjoe wrote:
In one of our recent labs for Earth Science, we tested to see which would heat up faster- a "rough" black painted can, or a metallic silver can.
...but since they were both made of the same metal can, they should have the same specific heat and cool down at the same rate, right?

But that might be the root of the problem right there. They are not both the same metal can, or at least not the heat-soaking surface. You said the black can was black because it was painted. Were you taking the temperature from the inside or on the surface of the outside?

I don't quite know the answer, but there are a bunch of random ideas like that I could throw out there.
Mar 8 2006, 10:41 am
In response to Loduwijk
Loduwijk wrote:
But that might be the root of the problem right there. They are not both the same metal can, or at least not the heat-soaking surface. You said the black can was black because it was painted. Were you taking the temperature from the inside or on the surface of the outside?

Sorry, I should have specified that. The data recorded was the temperature of the air inside the can.
Mar 8 2006, 12:35 pm
In response to Airjoe
How many times was the test preformed? Where both cans in identecal climates(AC vent could have been blowing on one). How acurate was the test? How much of a diffirence was there cool down times? These are all questions that could affect the outcome of the tests. If the tests where preformed only once, write a paper on the fact that one time is not enough for an acurate test, even in a high school.