Course sections

Section 1

Thermal properties & temperature

Thermal properties & temperature

Measurement of temperature

To measure the temperature of a substance, some of its physical properties should vary with temperature; they are the thermometric properties.
These properties could be volume, pressure, resistance etc.
For these physical properties, there should be some lower and upper fix points.

Mercury in glass thermometer

Volume of Mercury ∝ Change in temperature.
Lower fix point —–melting point of ice (0 ̊C)
Upper fix point —–boiling point of water (100 ̊C)

Sensitivity

It is the length of increase of the liquid per degree rise in temperature.
More sensitive means more noticeable expansion.
Sensitivity increases with decrease in diameter of the bore.

Range

It refers to the scope of temperature it can measure, or it is the minimum to maximum measurable temperature by a thermometer.

Specific heat capacity

Amount of energy needed to increase the temperature of one kilogram of a substance by one degree Celsius.

$c = \frac{Q}{m\Delta T}$

Q = Energy (J)
m = mass (Kg)
ΔT = change in temperature (C^o or K)
SI unit → $\frac{J}{Kg.K}$ or $\frac{J}{Kg.^{\circ}K}$

Thermal capacity (or Heat Capacity)

Amount of energy needed to change the temperature of a given mass of a substance by 1 ̊C.

$c = \frac{E}{\Delta T}$

SI unit is $\frac{J}{K}$ or $\frac{J}{^{\circ}C}$

$E = mc\Delta T$

$E = C\Delta T$

$C = mc$

Heat capacity = mass x specific heat capacity

Phase Change:

Specific latent heat

Amount of energy required per unit mass to change the phase of a material.

Specific heat latent of Fusion/Liquification

Amount of energy needed to change the phase of one kilogram of a solid to liquid at constant temperature.

$L_{f} = \frac{Q}{m}$

SI unit is $\frac{J}{kg}$

Specific heat latent of a Vaporization/Condensation

Amount of energy needed to change the phase of one kilogram of a liquid to gas at constant temperature.

$L_{v} = \frac{Q}{m}$

SI unit is $\frac{J}{kg}$