12. Temperature and heat Temperature and temperature scales.
Introduces temperature as average molecular kinetic energy and heat as energy transferred by a temperature difference, then compares the Celsius, Fahrenheit and Kelvin scales with their fixed reference points. Goes on to cover linear and volume thermal expansion, specific heat capacity, and the unusual properties of water such as its density maximum at 4°C. Closing sections describe calorimetry, thermostats and thermoregulators, sterilizers, and the idealised black body, with six diagrams included.
Topic 13 of 42 in the MU Sofia syllabus for Physics (Medicine, Year 1). The free AceMed note covers it in 9 sections, about 399 words (3 min of reading), with 9 flashcards.
In this note
Temperature and Heat – Temperature and Temperature Scales
Definition
Temperature Scales
Heat Expansion of Bodies
Thermal Properties of Water
Importance of Water for Living Organisms
Calorimetry
Thermostats and Thermoregulators
Sterilizers
Definition
Temperature and heat describe the behavior of bodies under thermal influence.
Temperature is a measure of the average kinetic energy of particles in a body.
Heat is the energy transferred between bodies due to a temperature difference.
Understanding their relationship is essential for explaining thermal expansion, heat capacity, water’s unique properties, and medical applications such as sterilization and thermal regulation.
Temperature Scales
Three main scales are used to measure temperature:
Celsius (°C):
0°C = freezing point of water.
100°C = boiling point of water (at standard atmospheric pressure).
Fahrenheit (°F):
32°F = freezing point of water.
212°F = boiling point of water.
Kelvin (K):
Absolute temperature scale.
0 K = absolute zero (no molecular motion).
Conversion
Heat Expansion of Bodies
When substances are heated, they expand; when cooled, they contract.
Linear expansion (solids): Change in length is proportional to original length and temperature change.
Volume expansion (solids and liquids):
Applications: bridges, railways, and medical instruments must account for thermal expansion to prevent damage.
Specific Heat Capacity
The amount of energy needed to raise the temperature of 1 kg of a substance by 1°C.
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