Why is metal heavier cold then when it is hot?
shawn9600 asked:
I work in a steel casting company and I have noticed that if a large piece of steel is heated to a high temp. and left on a scale, as it cools it gets heavier.
Hobby Metal Casting
I work in a steel casting company and I have noticed that if a large piece of steel is heated to a high temp. and left on a scale, as it cools it gets heavier.
Hobby Metal Casting
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Tags: 7 Responses to “Why is metal heavier cold then when it is hot?”
I wish i knew more about physics but, its because its like crumbling a peice of paper into a ball. The ball crunched is pulled down to the center of the earth more.
It is because of the thermal expansion of the metal.
When metal is hot its molecules spread out that lessen its weight while when it is cold its molecules compresses therefore giving more weight.
And aslo try to notice that when metal is hot it is longer than when it is cold.
I’m not sure I buy the crunching thing. That would only work if air resistance was a factor – which it isn’t. Newton’s Law of Universal Gravitation is dependent on mass and distance alone, not density. I don’t have any explanation for what’s happening, so I’d guess that it’s instrument error. The heat of the steel is probably expanding parts in the gauge of the scale, causing a false reading.
Maybe some air is dissolving or reacting with the metal while it’s hot.
And then there is buoyancy. Hot metal has a larger volume. That means it displaces more air and so the buoyancy is larger. But that is only a very small effect. I don’t think the scale is that sensitive.
It’s probably because the scale gets heated and then displays a wrong weight.
Hmm well let me see….Molecules are denser when they’re cold right? So the metal would get heavier. If it gets hot, the molecules will expand out more, thus the metal gets softer and lighter.
Wild & craaaaazi guess.
It doesn’t make sense as the weight of a piece doesn’t change with the temperature. The only thing that changes is the volume. When you heat it, it expands and so the density decreases and when you cool it, it contracts, decreasing its volume and in turn increasing the density. At the end when left on a scale you are mesuring the weight which should not change with the temperature. Maybe the heat affects the scale in some way….
It isn’t. It is more dense when cold because it will contract to smaller volume but retain the same mass.
Is the scale of metal material, too? It may be absorbing the heat of the casting, and the resulting expansion may be interfering with the proper working of the linkages of the scale. When the scale loses the heat, the mechanism goes back to its original dimensions and works properly, registering a different weight reading fo the casting than when it was hot.