Heat and Temperature

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Kinetic Theory of Matter Noun

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[ki-net-ik thee-uh-ree ov mat-er]

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Kinetic Theory of Matter

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The scientific model stating that all matter is composed of tiny particles which are in constant, random motion.

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Example: This diagram shows that matter is made of particles. As kinetic energy (heat) increases, particles move more freely, changing state from a fixed solid to a flowing liquid to a fast-moving gas.

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Temperature Noun

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[tem-per-uh-cher]

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Temperature

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A measure of the average translational kinetic energy of the particles in a substance, indicating its degree of hotness.

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Example: This image shows how a thermometer measures temperature, indicating a higher temperature for hot water being heated and a lower temperature for cold ice.

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Celsius scale Noun

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[sel-see-uhs skeyl]

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Celsius scale

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A temperature scale where water freezes at 0 degrees and boils at 100 degrees under standard atmospheric pressure.

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Example: This diagram shows key reference points on the Celsius scale using water: 0°C for freezing/melting, and 100°C for boiling.

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Fahrenheit scale Noun

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[far-en-hahyt skeyl]

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Fahrenheit scale

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A temperature scale where water freezes at 32 degrees and boils at 212 degrees under standard atmospheric pressure.

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Example: This diagram shows a thermometer with the Fahrenheit scale, highlighting that water freezes at 32°F and boils at 212°F, its two key reference points.

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Kelvin scale Noun

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[kel-vin skeyl]

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Kelvin scale

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The SI base unit of thermodynamic temperature, an absolute scale where zero Kelvin (0 K) represents absolute zero.

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Example: This diagram compares the Kelvin and Celsius temperature scales, showing that 0 K is absolute zero and that the size of a kelvin is the same as a Celsius degree.

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Absolute Zero Noun

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[ab-suh-loot zee-roh]

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Absolute Zero

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The theoretical lowest possible temperature at which particles of matter have minimal kinetic energy, defined as 0 Kelvin.

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Example: This diagram shows Absolute Zero (0 K) as the lowest point on the Kelvin, Celsius, and Fahrenheit temperature scales, far below the freezing point of water.

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Thermometer Noun

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[ther-mom-i-ter]

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Thermometer

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An instrument used for measuring temperature, typically relying on the thermal expansion of a substance like mercury or alcohol.

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Example: This diagram shows two thermometers, one in Celsius and one in Fahrenheit, comparing their scales using the freezing and boiling points of water.

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Heat Noun

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[heet]

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Heat

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The transfer of thermal energy between objects of different temperatures, flowing from the warmer object to the cooler one.

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Example: This diagram shows that heat is the transfer of thermal energy, which always flows from a hotter object to a colder object until they reach equilibrium.

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Thermal Energy Noun

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[thur-muhl en-er-jee]

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Thermal Energy

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The total internal energy of an object due to the kinetic energy of its atoms and/or molecules in random motion.

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Example: Adding thermal energy increases the kinetic energy of particles, causing a substance to change state from a solid (ordered particles) to a gas (disordered particles).

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Joule Noun

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[jool]

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Joule

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The standard international (SI) unit of work or energy, used to measure quantities like heat and thermal energy.

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Example: This image shows a calculation where electrical energy in Joules is found by multiplying power in Watts by time in seconds.