Thermal Properties of Matter MCQs for NEET — Physics Questions with Answers

Referring to Table 10.3 (Specific heat capacity of some substances), Aluminium has a specific heat capacity of 900.0 J kg$^{-1}$ K$^{-1}$, Copper 386.4 J kg$^{-1}$ K$^{-1}$, Iron 450 J kg$^{-1}$ K$^{-1}$, and Lead 127.7 J kg$^{-1}$ K$^{-1}$. The substance with the highest specific heat capacity requires the most heat for a given temperature change and mass. Aluminium has the highest value among the given options.

From the NCERT text, specific heat capacity is defined as $s = \frac{\Delta Q}{m\Delta T}$. Heat capacity (S) is defined as $S = \frac{\Delta Q}{\Delta T}$. Therefore, by multiplying $s$ by $m$, we get $ms = m \frac{\Delta Q}{m\Delta T} = \frac{\Delta Q}{\Delta T} = S$. So, $S = ms$.

The NCERT text clearly states: 'Consider a solid of N atoms, each vibrating about its mean position. An oscillator in one dimension has average energy of $2 \times \frac{1}{2} k_B T = k_B T$. In three dimensions, the average energy is $3 k_B T$.' For a mole, this leads to $U = 3 RT$ and thus $C = 3R$. Each degree of freedom of a 3D harmonic oscillator (vibration) contributes $\frac{1}{2}k_BT$ for kinetic and $\frac{1}{2}k_BT$ for potential energy, totaling $k_BT$ per dimension, and thus $3k_BT$ for 3 dimensions per atom.

Heat lost or gained is given by $Q = ms\Delta T$. The mass of the aluminium sphere ($m_1$) is 0.047 kg, the specific heat capacity is $s_{Al}$, and the change in temperature ($\Delta T$) for the aluminium sphere is from 100 °C down to 23 °C, so $\Delta T = (100 - 23)$ °C. Thus, $Q_{lost}$ by aluminium $= m_1 s_{Al} (T_{initial} - T_{final}) = 0.047 \times s_{Al} \times (100 - 23)$.

According to the NCERT text, 'The commonly used property is variation of the volume of a liquid with temperature. For example, in common liquid–in–glass thermometers, mercury, alcohol etc., are used whose volume varies linearly with temperature over a wide range.'

The NCERT text states, 'For the definition of any standard scale, two fixed reference points are needed.'

The context mentions, 'The ice point and the steam point of water are two convenient fixed points and are known as the freezing and boiling points, respectively.'

The NCERT text specifies, 'The ice and steam point have values 32 °F and 212 °F, respectively, on the Fahrenheit temperature scale.'

The text explicitly states, 'The SI unit of heat energy transferred is expressed in joule (J) while SI unit of temperature is Kelvin (K), and degree Celsius (°C) is a commonly used unit of temperature.'

The summary section clearly states, 'The Celsius temperature ($t_C$) and the Fahrenheit temperature ($t_F$) are related by $t_F = (9/5)t_C + 32$'.