Assertion (A): Specific heat of substance is property of material.
Reason (R): Specific heat also depends on the condition of the experiment. The way in which heat is supplied to the body.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Specific heat is an intrinsic property of a substance, dependent only on the material itself and its phase, not on experimental conditions or how heat is supplied. Thus, Assertion (A) is true. Reason (R) is false. Therefore, (A) is true but (R) is false.
Assertion (A): Specific heat for melting Ice is infinite.
Reason (R): In isothermal process specific heat of substance is infinite.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Specific heat is defined as \(c = \frac{Q}{m \Delta T}\). During melting (a phase change), the temperature \(\Delta T\) remains constant, meaning \(\Delta T = 0\). Hence, the specific heat \(c\) becomes infinite. Both assertion and reason are true, and the reason explains the assertion.
Assertion (A): Specific heat for melting Ice is infinite.
Reason (R): In isothermal process specific heat of substance is infinite.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Specific heat is \(C = \frac{Q}{m \Delta T}\). During melting, \(\Delta T = 0\), so \(C\) is infinite. Melting is an isothermal process, so both A and R are true and R explains A.
Assertion (A): Two bodies at different temperatures, if brought in contact do not necessary settle to the mean temperature.
Reason (R): The two bodies may have different thermal capacities.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
The final temperature of two bodies in contact depends on their thermal capacities \(m\times c\). If capacities are unequal, the final temperature will not be the mean. Both A and R are true, and R explains A.
Assertion (A): During phase change temperature of the substance remains constant.
Reason (R): Internal energy of the substance during change of phase remains constant.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true; temperature is constant during phase change. Reason (R) is false; internal energy changes as latent heat is absorbed/released to alter molecular potential energy.
Assertion (A): An ice skater can slide over ice smoothly if the skate blades are sharp.
Reason (R): Melting point of ice decreases with increase in pressure.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Sharp blades increase pressure, lowering ice's melting point (regelation). A thin water layer forms, reducing friction, allowing smooth sliding. Thus, R correctly explains A.
Assertion (A): Melting of solid causes no change in internal kinetic energy.
Reason (R): Latent heat is the heat required to melt a unit mass of solid.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
During melting at constant temperature, the average kinetic energy of molecules (related to temperature) remains constant.
Latent heat increases potential energy. So (A) is true. (R) correctly defines latent heat.
However, (R) does not explain why kinetic energy remains unchanged.
Assertion (A): If one gram of ice at \(0^{\circ}\text{C}\) is mixed with one gram of water at \(80^{\circ}\text{C}\), then the final temperature of mixture will be \(0^{\circ}\text{C}\).
Reason (R): Latent heat of ice is \(540\text{ cal/g}\).
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Heat to melt 1g ice at \(0^{\circ}\text{C}\text{ is }1 \times 80\text{ cal/g} = 80\text{ cal}\). Heat from 1g water cooling from \(80^{\circ}\text{C}\text{ to }0^{\circ}\text{C}\text{ is }1 \times 1 \times 80 = 80\text{ cal}\). All ice melts, final temperature is \(0^{\circ}\text{C}\). So (A) is true.
Latent heat of fusion of ice is \(80\text{ cal/g}\), not \(540\text{ cal/g}\). So (R) is false.
Assertion (A): Water can be made to boil without heating.
Reason (R): Boiling point of water is lowered by decreasing pressure.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Boiling occurs when vapor pressure equals external pressure. Reducing external pressure lowers the boiling point of water. Thus, water can be made to boil at room temperature or even lower without external heating. Both (A) and (R) are true, and (R) correctly explains (A).
Assertion (A): When a hot liquid is mixed with a cold liquid, the temperature of the mixer is undefined for some time and then becomes nearly constant.
Reason (R): If two bodies at different temperature are mixed in a calorimeter, the total energy of the two bodies remains conserved.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
When liquids of different temperatures are mixed, it takes time to reach thermal equilibrium, so temperature is not uniform initially. So (A) is true. In an ideal calorimeter, total energy is conserved. So (R) is true. However, (R) does not explain the time-dependent nature of temperature equilibration in (A).