Translations of Encyclopedia about Physics

Heat Expansion of Objects

Every object reacts differently to heat, depending on the object’s density, its composition and the pressure which acts on it.

By rule, solid objects have a higher density than do liquids and gases because the atoms within solid objects are closer together and work stronger forces on one another. The density of solid objects is based on attracting forces acting between individual particles, atoms or molecules, within the object.

If some physical force, such as pressure, acts on an object, these particles come closer to one another. This results in an opposing force, which we refer to as pressure. On the other hand, when we pull on a substance, the particles become farther apart, creating a force we refer to as stress.

Not only physical forces but also changes in temperature affect the structure of an object. If we add heat to an object, we are adding kinetic energy to its particles which makes them vibrate faster and expands the object.

If a certain temperature is surpassed, solid objects change the phase they are in, turning into a liquid or, in some cases, turning into a gas without first turning into a liquid. In the liquid state, an object loses its solid state. The distance between the atoms and molecules of an object are farther apart in its liquid or gas states than in its solid state and the particles work a smaller force on each other, allowing them to slide past each other and make the substance a liquid.

In the same way that solid substances expand under heat, so do liquid and gaseous substances. With enough heat added, liquids evaporate and turn into a gaseous form. If we maintain gaseous or liquid substances at the same volume while adding heat to them, their pressure increases.

Changes in temperature to gaseous substances can be easily observed in a closed vessel. If we heat up gas in a vessel, the kinetic energy of its particles increases, where the gas’s molecules begin to move faster, hitting and bouncing against the walls of the vessel and against themselves until the temperature of the substance within the vessel increases.

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