A flat piece of metal has a hole in it. If the temperature increases, what happen to the size of the hole?

Question

will the size of the hole increase, decrease, or stay the same? Explain.

Answer 1

I would think that it would increase. When something gains heat, the molecules inside it move at a faster rate, meaning that it grows larger. I believe this is right, but not 100% sure.

Answer 2

Mecinimi is right: as the temperature increases the hole increases in size. Since all distances between given material particles (atoms) expand linearly with increase of temperature, so  do atoms located right on the circumference of the hole.  And since the distance between them increases, so does the hole.

You apply this concept when you heat the metal lid on a jar by holding it over a flame on the stove in order to remove it more easily.

Answer 3

This question is asked in every beginning physics class. You would think the hole would get smaller, but that is not the case: as something expands it expands in all dimensions, meaning the circumference of the hole will increase.

Look at it this way: another way to see what would happen if the metal expands is to look at it with a magnifying glass. What happens to the hole in this case? This time your intuition is correct - the hole is magnified with everything else.

Answer 4

The size of the hole decreases.  This is best shown with a metal ring and ball where the ball just barely makes it through. If you heat the metal ring (and not the ball as suggested in the first responders link) the ring has to expand in all directions.  There is a volume change due to increased molecular motion that has to change in all directions when under a constant pressure.  While the outside of the ring gets bigger, the inside of the ring gets smaller since that part of the ring expands inward.  The ball will no longer fit through the ring. This is sometime a demo in basic thermodynamics or physics classes (I have performed it myself).  So back to the flat metal, it must expand in all directions, which means the hole gets smaller (outward and inward expansion).

Answer 5

It increases.  Try one of these ball and ring demonstrations.

http://scientificsonline.com/product.asp...

http://www.science-is.com/misc.htm

Or you could just watch a couple of physics teachers perform the experiment on Youtube:

http://www.youtube.com/watch?v=wFIgskt1Y...

or

http://www.youtube.com/watch?v=V0ETKRz2U...

EDIT - In response to the two people below (who were wrong) and who gave me 2 thumbs down - watch the 2nd video.  The metal does expand on the inside of the hole towards the center, but overall the hole does get bigger.

Answer 6

The size of the hole also increases.

This is a principle used to 'sweat' a sleeve onto a turbine (or other) shaft.

The sleeve is heated, slipped over the shaft and, as it cools and contracts, it grabs the shaft and stays in position.