Temperature

Temperature Effects

• Physical properties of materials are affected by temperature, including phase, density, solubility, vapor pressure, electrical conductivity, hardness, and thermal conductivity.
• Chemical reaction rates and extent are influenced by temperature.
• Thermal radiation emitted from an object is dependent on its temperature.
• Air temperature impacts all living organisms.
• The speed of sound in a gas is proportional to the square root of the absolute temperature.

Temperature Scales

• Celsius scale defines 0°C as the freezing point and 100°C as the boiling point of water at sea level.
• Kelvin scale has absolute zero at 0K and is essential in scientific applications.
• Fahrenheit scale is commonly used in the United States with water freezing at 32°F and boiling at 212°F.
• Celsius and Kelvin scales have a numerical offset of 273.15.
• Temperature scales require two reference points for definition.

Absolute Zero and Absolute Scales

• At absolute zero (0K or −273.15°C), no heat can be extracted from matter.
• Matter at absolute zero has no macroscopic thermal energy but retains quantum-mechanical zero-point energy.
• The lowest experimentally reached temperature is 38pK.
• Absolute zero is equal to −459.67°F.
• Kelvin scale is an absolute temperature scale independent of thermometric substances and mechanisms.

Kelvin Scale

• Named after Lord Kelvin, the Kelvin scale (K) is an absolute temperature scale.
• The zero point of the Kelvin scale is at absolute zero.
• The Kelvin scale is defined using the Boltzmann constant.
• It is widely used in scientific measurements.
• The Kelvin scale has been defined through particle kinetic theory since May 2019.

Theoretical Temperature Scales and Measurement Techniques

• Theoretically based temperature scales rely on kinetic theory and thermodynamics.
• Kelvin temperature is defined based on the motions of microscopic particles in a body.
• The Boltzmann constant plays a crucial role in defining temperature.
• Measurement techniques include speed of sound measurement, analysis of escaping particles, and velocity spectrum measurement.
• Good samples can sometimes be obtained for measurement.

Temperature Data Sources