Class 11 Physics Important Chapter 11 Thermal Properties of Matter Solutions English Medium As Per AHSEC New Syllabus to each chapter is provided in the list so that you can easily browse through different chapters NCERT Class 11 Physics Important Solutions and select need one. AHSEC Class 11 Physics Additional Notes English Medium Download PDF. HS 1st Year Physics Important Solutions in English.
Class 11 Physics Important Chapter 11 Thermal Properties of Matter
Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. NCERT Class 11 Physics Additional Question Answer are part of All Subject Solutions. Here we have given HS 1st Year Physics Important Notes in English for All Chapters, You can practice these here.
Thermal Properties of Matter
Chapter: 11
| IMPORTANT QUESTION AND ANSWER |
Answer the Following Questions:
1. What is the unit of heat?
Ans: The SI unit of heat is the joule (J).
2. What is the SI unit of temperature?
Ans: The SI unit of temperature is the Kelvin (K).
3. What is the relationship between Celsius and Fahrenheit scales?
Ans: The Celsius and Fahrenheit scales are related by the equation:
where tF is the temperature in Fahrenheit and tC is the temperature in Celsius.
4. What is the coefficient of linear expansion?
Ans: The coefficient of linear expansion (αl) is the fractional change in length per unit change in temperature of a material.
It is given by:
where Δl is the change in length, l is the original length, and ΔT is the change in temperature.
5. State Newton’s Law of Cooling.
Ans: Newton’s Law of Cooling states that the rate of cooling of a body is directly proportional to the excess temperature of the body over its surroundings, i.e., dQ/dt∝(T2−T1), where T2 is the temperature of the body and T1 is the temperature of the surroundings.
6. What is the ideal gas law? Derive it from Boyle’s and Charles’ laws.
Ans: The ideal gas law combines Boyle’s law, Charles’ law, and Avogadro’s law into one equation. Boyle’s law states that at constant temperature, P∝1V , where P is pressure and V is volume. Charles’ law states that at constant pressure, V∝T, where T is the temperature. By combining these two laws, the ideal gas law can be written as:
PV = nRT
where P is pressure, V is volume, nnn is the number of moles, R is the gas constant, and T is the temperature in Kelvin. The ideal gas law explains the behavior of gases and shows the relationship between pressure, volume, and temperature.
7. What is thermal expansion? Derive the formula for linear expansion.
Ans: Thermal expansion is the change in the dimensions of a material when its temperature is altered. For linear expansion, when the temperature of a solid object increases, its length increases proportionally.
The change in length is given by:
Where Δl is the change in length, αl is the coefficient of linear expansion, l0 is the original length, and ΔT is the change in temperature. This formula shows that the change in length is directly proportional to the temperature change and the original length.
8. Explain the concept of latent heat of fusion with an example.
Ans: The latent heat of fusion is the amount of heat required to change a unit mass of a solid into a liquid at its melting point without changing its temperature. For example, to melt 1 kg of ice at 0°C, a certain amount of heat must be added to overcome the forces holding the ice molecules together. The latent heat of fusion of ice is 3.33 × 10⁵ J/kg. This heat goes into breaking the bonds between the ice molecules, causing it to melt into water at the same temperature.
9. State and explain the Stefan-Boltzmann Law of radiation.
Ans: The Stefan-Boltzmann Law states that the total energy radiated by a black body is directly proportional to the fourth power of its absolute temperature.
The law is mathematically given by:
Where H is the radiated energy per unit time, A is the surface area of the body, T is the absolute temperature, and σ is the Stefan-Boltzmann constant, 5.67×10−8 W m−2 K−4. This law is important for understanding the radiation of heat from bodies, such as the Sun or a hot object.
10. Explain the working principle of a liquid-in-glass thermometer.
Ans: A liquid-in-glass thermometer works on the principle that the volume of a liquid (such as mercury or alcohol) changes with temperature. When the temperature increases, the liquid expands, and when the temperature decreases, the liquid contracts. The liquid is contained in a capillary tube, and as the liquid expands or contracts, it moves along the scale, giving a reading of the temperature. The thermometer is calibrated using two fixed points: the freezing point and boiling point of water, which are used to define the temperature scale.
11. Eskimos make double walled ice houses. Why?
Ans. The air enclosed between the walls is a bad conductor of heat. This air reduces the out-flow of heat from inside the houses. Thus, the people living in these houses feel warmer.
12. A cloudy night is hotter than a clear sky night. Why?
Ans. This is because in the cloudy night, heat radiated out from earth is reflected back to the earth. Hence, temperature of earth does not fall.
13. What is specific heat capacity? Derive the formula to calculate it.
Ans: Specific heat capacity is the amount of heat required to raise the temperature of 1 kg of a substance by 1°C (or 1 K). The formula to calculate specific heat capacity is given by:
Q = mcΔT
where Q is the heat absorbed or released, m is the mass of the substance, c is the specific heat capacity, and ΔT is the change in temperature. This formula shows that the heat required depends on the mass of the substance, its specific heat capacity, and the temperature change.
14. Explain the concept of thermal conductivity with an example.
Ans: Thermal conductivity is a property of a material that indicates its ability to conduct heat. It is defined as the amount of heat transferred through a unit area of the material per unit time, per unit temperature gradient.
Mathematically, it is given by:
Where H is the rate of heat transfer, K is the thermal conductivity, A is the cross-sectional area, L is the length of the material, and ΔT is the temperature difference. For example, metals like copper have high thermal conductivity and transfer heat quickly, while materials like wood have low thermal conductivity and act as insulators.
15. Explain the concept of absolute zero temperature.
Ans: Absolute zero is the theoretical temperature at which the particles of a substance have minimal motion, and it is considered to be the lowest possible temperature. It is defined as 0 K on the Kelvin scale, equivalent to -273.15°C. At this temperature, a gas would have zero volume, according to the ideal gas law. Absolute zero is unattainable in practice, but it serves as a fundamental reference point in thermodynamics.
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