MadSci Network: Chemistry |
My son recently completed a science experiment, as follows: He placed one plate face-down on a baking sheet on the floor. He placed a second plate face-up on top of the first (so that the plates were back-to-back). He then attached a suction cup and a string to the top plate. At the other end of the string was a paper cup. The string was hung over the top of a lever (creating sort of a "scale" with the paper cup on side and the plate on the other). He tested to see how many pennies were needed to lift the top plate, first when the plates were dry, and then when the bottoms of the plates were wet with water of varying temperatures. As expected, it took more pennies to separate the wet plates than the dry plates, but we wer surprised to find that it took the most pennies (around 300) to separate the plates when wet with the hottest water we tested (140 degrees), and it took the fewest pennies (around 120) to separate the plates when wet with the coldest water we tested (37 degrees). Can you explain why? Thank you.
Re: How and why does water temperature affect cohesion and adhesion?
Try the links in the MadSci Library for more information on Chemistry.