Does increasing the temperature of an object increase it's mass?

• mcafej
In summary: That's exactly right. The compressed spring would have more mass due to the added energy from the compression.
mcafej
Ok, so I was just thinking about einsteins famous equation E=mc^2, and I was just wondering, if I were to take, say a rock or piece of metal. If I were to weigh it, and get it's mass, I could compute how much energy it contains. However, if I were to add heat to the rock or piece of metal by putting it into a fire to just heat it up, wouldn't the amount of energy that the rock or metal contains be higher, and so wouldn't the mass be higher (since the speed of light is constant, the only thing that can increase when the energy increases is mass, right?)? Anyways, maybe I'm missing an obvious point, but I was just curious about this, so any clarification would be great.

You are absolutely correct. The measured mass would increase if you heat an object up.

Just remember that the equation E=mc^2 only applies to objects at rest. Objects in motion use the equation $E^2=m^2c^4+p^2c^2$.

mcafej said:
Ok, so I was just thinking about einsteins famous equation E=mc^2, and I was just wondering, if I were to take, say a rock or piece of metal. [..] if I were to add heat to the rock or piece of metal [..], wouldn't the amount of energy that the rock or metal contains be higher, and so wouldn't the mass be higher [..]? [..] any clarification would be great.

Yes that is correct; the kinetic energy of the vibrating atoms in that object adds to its mass. (I don't know if it has ever been possible to measure this effect.)

http://www.fourmilab.ch/etexts/einstein/E_mc2/www/

and a discussion of temperature:
https://en.wikipedia.org/wiki/Thermodynamic_temperature

Does this also mean that a steel spring would be measured heavier in a compressed state than in a non-compressed state as it has stored energy?

JustinRyan said:
Does this also mean that a steel spring would be measured heavier in a compressed state than in a non-compressed state as it has stored energy?

Yep!

1. Does increasing the temperature of an object automatically increase its mass?

No, increasing the temperature of an object does not automatically increase its mass. Mass is a measure of the amount of matter in an object, while temperature is a measure of the average kinetic energy of the particles in the object. These two properties are not directly related.

2. Why do some objects appear to have a greater mass when heated?

When an object is heated, its particles gain kinetic energy and vibrate faster. This increased motion can cause the particles to spread out and take up more space, resulting in a slight increase in the object's volume. However, the mass of the object remains the same.

3. Is it possible for an object's mass to decrease when heated?

Yes, it is possible for an object's mass to decrease when heated. Some substances, such as water, undergo a phase change when heated. In the case of water, it changes from a solid (ice) to a liquid (water) when heated. During this phase change, the mass of the substance remains the same, but its density decreases, resulting in a decrease in its overall mass.

4. How does the density of an object change when it is heated?

The density of an object may change when it is heated, depending on the substance. As mentioned before, some substances undergo a phase change when heated, resulting in a change in density. In general, as the temperature of a substance increases, its particles gain more kinetic energy and spread out, causing a decrease in density. However, this is not always the case and can vary depending on the substance.

5. Can an object's mass increase without changing its temperature?

Yes, an object's mass can increase without changing its temperature. This can occur through processes such as chemical reactions, where mass is conserved but the composition of the object changes. For example, when iron rusts, it combines with oxygen from the air, resulting in an increase in mass without a change in temperature.

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