Changes of State and Thermodynamics

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Thermal Equilibrium Noun

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[thur-muhl ee-kwi-lib-ree-uhm]

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Thermal Equilibrium

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The state where two objects in contact have the same temperature, resulting in no net transfer of thermal energy.

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Example: A hot object (100°) and a cold object (0°) transfer heat until they both reach the same middle temperature (50°), achieving thermal equilibrium.

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Specific Heat Noun

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[spuh-sif-ik heet]

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Specific Heat

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The amount of heat energy required to raise the temperature of one kilogram of a substance by one Kelvin.

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Example: A small mass of water heats up faster than a large mass, showing how substances with high specific heat, like water, resist temperature changes.

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Calorimeter Noun

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[kal-uh-rim-i-ter]

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Calorimeter

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An insulated, closed-system device used to measure the amount of thermal energy absorbed or released during a chemical reaction.

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Example: This diagram shows a calorimeter, an insulated container (styrofoam cups) with a thermometer, used to measure heat changes during a physical or chemical process.

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Melting Point Noun

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[mel-ting point]

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Melting Point

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The specific temperature at which a substance changes its state from a solid to a liquid at atmospheric pressure.

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Example: This heating curve shows that as heat is added, a solid's temperature rises until it reaches the melting point, where it stays constant while turning into a liquid.

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Boiling Point Noun

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[boil-ing point]

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Boiling Point

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The specific temperature at which a substance changes its state from a liquid to a gas at atmospheric pressure.

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Example: This image shows water in a pot being heated until it boils, turning into steam. The thermometer indicates this change of state happens at 100°C (212°F), which is water's boiling point.

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Heat of Fusion Noun

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[heet uv fyoo-zhuhn]

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Heat of Fusion

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The amount of thermal energy needed to change one kilogram of a substance from a solid to a liquid.

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Example: This image shows an ice cube melting, which is the phase change from solid to liquid. Heat of fusion is the energy absorbed to make this change happen.

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Heat of Vaporization Noun

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[heet uv vey-per-uh-zey-shuhn]

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Heat of Vaporization

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The amount of thermal energy needed to change one kilogram of a substance from a liquid to a gas.

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Example: Adding heat to liquid water at its boiling point (100°C) provides the energy needed for it to change state into a gas (vapor).

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Heating Curve Noun

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[hee-ting kurv]

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Heating Curve

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A graph that plots the temperature of a substance against the amount of heat energy added, showing phase changes.

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Example: This graph shows how a substance's temperature changes as heat is added, including plateaus where temperature stays constant during melting and evaporation.

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Thermodynamics Noun

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[thur-moh-dahy-nam-iks]

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Thermodynamics

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The branch of physics that deals with the relationships between heat, work, and other forms of energy in a system.

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Example: This diagram shows that heat energy naturally moves from a hot object (red cube) to a colder object (blue cube), a core principle of thermodynamics.

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Heat Engine Noun

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[heet en-jin]

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Heat Engine

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A device that converts thermal energy from a high-temperature source into mechanical work, while expelling some waste heat.

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Example: This diagram shows how hot steam pushes against the blades of a turbine, causing it to spin and generate mechanical work, a key part of a heat engine.