NEET Practice Questions (MCQs) with Answers & Solutions

From the NCERT text: 'The old unit of heat was calorie. One calorie was earlier defined to be the amount of heat required to raise the temperature of 1g of water by 1°C.' It further refines this to '1g of water from 14.5 °C to 15.5 °C' for a precise definition.

The NCERT text explicitly states: 'For an ideal gas, the molar specific heat capacities at constant pressure and volume satisfy the relation $C_p - C_v = R$' where R is the universal gas constant.

Given $\Delta Q = ms \Delta T$. If $\Delta Q$ and $m$ are constant for both substances, then $s \propto 1/\Delta T$. A smaller temperature change ($\Delta T$) implies a larger specific heat capacity ($s$). Therefore, $s_A > s_B$.

The NCERT text states: 'Since in SI units, we use the unit joule for heat, work or any other form of energy, the term mechanical equivalent is now superfluous and need not be used.' It was essentially a conversion factor between calories and joules.

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 World Health Organisation (WHO), reproductive health means a total well-being in all aspects of reproduction, i.e., physical, emotional, behavioural and social. Economic well-being is not explicitly mentioned in this definition.

India was amongst the first countries in the world to initiate action plans and programmes at a national level to attain total reproductive health as a social goal. These programmes called ‘family planning’ were initiated in 1951.