WBBSE Class 10 Physical Science Notes Solutions Chapter 4 Thermal Phenomena | WBBSE Class 10 Physical Science Chapter 4 Notes in ENGLISH
WBBSE Class 10 Physical Science Chapter 4 Question Answer – Thermal Phenomena
Certainly! Here's a more polished version:
### Short Answer Type Questions:
**Question 1.**
*What do you mean by heat?*
**Answer:**
Heat is a form of energy that produces the sensation of warmth.
**Question 2.**
*What are the different types of motion?*
**Answer:**
Different types of motions include:
- Translational motion
- Vibrational motion
- Rotational motion
**Question 3.**
*What is the definition of heat with respect to motion?*
**Answer:**
The definition of heat with respect to motion states that heat possessed by a body is the total thermal energy of the body, which is the sum of kinetic energies of all the individual molecules forming the body due to translational, vibrational, and rotational motions of the molecules.
**Question 4.**
*What do you mean by calorie?*
**Answer:**
A Calorie is the quantity of heat required to raise the temperature of 1 gram of water through 1°C.
**Question 5.**
*What is temperature?*
**Answer:**
Temperature is the thermal condition of a body that determines the direction of the flow of heat when the body is placed in thermal contact with another body.
**Question 6.**
*What is the upper fixed point of a thermometer?*
**Answer:**
The upper fixed point is the temperature of steam from water boiling under a pressure of 76 cm of mercury at sea level and 45° latitude.
**Question 7.**
*What is the lower fixed point of a thermometer?*
**Answer:**
The lower fixed point is the temperature of melting ice under a pressure of 76 cm of mercury at sea level and 45° latitude.
**Question 8.**
*What is the fundamental interval?*
**Answer:**
The fundamental interval is the difference between the fixed points of a scale.
**Question 9.**
*What do you mean by thermal expansion?*
**Answer:**
Thermal expansion is when the dimensions of all substances generally increase with an increase in temperature.
**Question 10.**
*What are the types of expansions in solids?*
**Answer:**
Types of expansions in solids include linear expansions, superficial expansions, and volume expansions.
**Question 11.**
*What is the apparent expansion of the liquid?*
**Answer:**
Apparent expansion of the liquid is when the expansion of the liquid is measured, ignoring the expansion.
**Question 12.**
*What is the real expansion of the liquid?*
**Answer:**
Real expansion of the liquid is when the actual expansion of the liquid is measured by considering the expansion of the containing vessel.
**Question 13.**
*What is the conclusion of Hope’s experiment?*
**Answer:**
The conclusion of Hope’s experiment is that water at the bottom, which is densest at 4°C, experiences a slightly lower temperature over time due to heat loss by conduction to the upper regions.
**Question 14.**
*What is molar specific heat at constant volume (Cv)?*
**Answer:**
Molar specific heat at constant volume (Cv) is the amount of heat required to raise the temperature of one mole of the gas through one degree, keeping the volume constant.
**Question 15.**
*What is molar specific heat at constant pressure (Cp)?*
**Answer:**
Molar specific heat at constant pressure (Cp) is the amount of heat required to raise the temperature of one mole of the gas through one degree, keeping the pressure constant.
**Question 16.**
*What is water equivalent of a body?*
**Answer:**
Water equivalent of a body is the mass of water which will be heated through one degree by the amount of heat that raises the temperature of the body through one degree.
**Question 17.**
*What is Regelation?*
**Answer:**
Regelation is the phenomenon of melting ice under pressure and freezing again on releasing the pressure.
**Question 18.**
*What do you mean by vapor pressure of a liquid?*
**Answer:**
Vapor pressure is the pressure exerted by a vapor when it evaporates at a specific temperature.
**Question 19.**
*What is conduction of heat?*
**Answer:**
Conduction is the process of the transfer of heat through a substance without any detectable motion of the particles of the substance.
**Question 20.**
*What is convection of heat?*
**Answer:**
Convection of heat is the process by which heat is transmitted through a liquid or gas from a hotter point to a colder point due to the bodily motion of the heated particles.
**Question 21.**
*What is radiation of heat?*
**Answer:**
Radiation is the transmission of heat from a hot body to a cold body without the help of any medium and without appreciable heating at the intervening medium, if any.
**Question 22.**
*What is a perfectly black body?*
**Answer:**
A perfectly black body is one that absorbs completely the radiations of all wavelengths incident upon it.
**Question 23.**
*What is the greenhouse effect?*
**Answer:**
The greenhouse effect is an example of selective absorption of heat by glass. The amount of heat transmitted through a substance depends on the temperature of the source of heat.
**Question 24.**
*What do you mean by global warming?*
**Answer:**
Global warming is the increase in Earth's average surface temperature due to the buildup of greenhouse gases in the atmosphere, leading to changes in climate patterns.
### Broad Answer Type Questions:
**Question 1.**
*State the units and dimensions of different coefficients.*
**Answer:**
The units and dimensions of different coefficients are essential in understanding the thermal properties of materials and substances. Here is a breakdown:
1. **Coefficient of Linear Expansion (α):**
- *Unit:* K⁻¹ (per degree Celsius or Kelvin)
- *Dimension:* [M⁰ L¹ T⁻² θ⁻¹]
2. **Coefficient of Superficial Expansion (β):**
- *Unit:* K⁻¹ (per degree Celsius or Kelvin)
- *Dimension:* [M⁰ L¹ T⁻² θ⁻¹]
3. **Coefficient of Volume Expansion (γ):**
- *Unit:* K⁻¹ (per degree Celsius or Kelvin)
- *Dimension:* [M⁰ L¹ T⁻² θ⁻¹]
4. **Specific Heat at Constant Volume (Cv):**
- *Unit:* J kg⁻¹ K⁻¹ (joules per kilogram per Kelvin)
- *Dimension:* [M¹ L² T⁻² θ⁻¹]
5. **Specific Heat at Constant Pressure (Cp):**
- *Unit:* J kg⁻¹ K⁻¹ (joules per kilogram per Kelvin)
- *Dimension:* [M¹ L² T⁻² θ⁻¹]
6. **Water Equivalent:**
- *Unit:* kg (kilograms)
- *Dimension:* [M¹ L⁰ T⁰ θ⁰]
These coefficients and specific heats play a crucial role in describing how a substance responds to changes in temperature and heat transfer.
### Very Short Answer Type Questions:
**Question 1.**
*Is it possible for a body to have negative temperature in the Kelvin scale?*
**Answer:**
No, because below 0 K temperature, the volume of a gas would be negative, which is impossible.
**Question 2.**
*What is the SI unit of heat?*
**Answer:**
The SI unit of heat is Joule.
**Question 3.**
*Mention the CGS unit of heat?*
**Answer:**
The CGS unit of heat is calorie.
**Question 4.**
*Is the volume coefficient of a gas different from its pressure coefficient?*
**Answer:**
No, they are equal.
**Question 5.**
*What is the value of the specific heat of water in SI units?*
**Answer:**
4200 J kg⁻¹ K⁻¹.
**Question 6.**
*Is it possible that heat is supplied to a body without changing the temperature?*
**Answer:**
Yes, during a change of state, there is no change in temperature although heat is supplied.
**Question 7.**
*What is the value of the latent heat of fusion of ice in the CGS system?*
**Answer:**
80 cal g⁻¹.
**Question 8.**
*Do water and ice have the same specific heat?*
**Answer:**
No, the specific heat of water is 1 cal g⁻¹ °C⁻¹, and that of ice is 0.5 cal g⁻¹ °C⁻¹.
**Question 9.**
*What is the difference between 1° C and 1 C°?*
**Answer:**
1° C is a particular temperature, while 1 C° is the interval of one degree Celsius of temperature.
**Question 10.**
*What is the lower fixed point of a Celsius scale?*
**Answer:**
0° C.
**Question 11.**
*What is the upper fixed point of a Fahrenheit Scale?*
**Answer:**
212° F.
**Question 12.**
*Is there any upper fixed point in the Kelvin Scale?*
**Answer:**
273.13 K, which is the triple point of water.
**Question 13.**
*Which is more expansible - solid, liquid, or gas?*
**Answer:**
Gas.
**Question 14.**
*A metal scale does not give the correct value at all temperatures - explain.*
**Answer:**
At different temperatures, the distance between different marks of the metal scale is different due to thermal expansion of the metal.
**Question 15.**
*The Coefficient of linear expansion of a metal is 19 × 10⁻⁶° C⁻¹. What is its value per degree Fahrenheit?*
**Answer:**
α = 59 × 19 × 10⁻⁶ = 10.6 × 10⁻⁶ °F.
**Question 16.**
*Is the coefficient of linear expansion possible in the case of a liquid?*
**Answer:**
No, liquid has no definite length.
**Question 17.**
*There is a coefficient of apparent expansion in a liquid but not in a gas - why?*
**Answer:**
For the same rise of temperature, a liquid expands only about 10 times that of a solid, while gas expands about 100 times that of a solid. So, the expansion of the vessel can be neglected in the case of gases.
**Question 18.**
*What is anomalous expansion of water?*
**Answer:**
In the range of 0°C to 4°C, the volume of water decreases instead of increasing, like other liquids. This is known as the anomalous expansion of water.
**Question 19.**
*Why are there two types of coefficients of expansion of a gas?*
**Answer:**
The change of temperature is very much affected by both its pressure and volume, so gas has two types of coefficients of expansion.
**Question 20.**
*Is a temperature lower than absolute zero of temperature possible?*
**Answer:**
No.
**Question 21.**
*What is thermal conductivity of a perfect heat conductor?*
**Answer:**
Infinite.
**Question 22.**
*What is thermal conductivity of a perfect heat insulator?*
**Answer:**
Zero.
**Question 23.**
*Can heat flow by convection take place in a straight line?*
**Answer:**
In convection, heat travels in a straight or curved path in the upward direction only.
**Question 24.**
*Can convection take place in a solid?*
**Answer:**
No, for convection, a fluid medium is required.
**Question 25.**
*What is the absorbing power of a perfectly black body?*
**Answer:**
One.
**Question 26.**
*What is the reflecting power of a perfectly black body?*
**Answer:**
Zero.
**Question 27.**
*What is a perfectly black body?*
**Answer:**
A body that absorbs all radiations incident to it.
**Question 28.**
*By which mode does heat reach the earth from the Sun?*
**Answer:**
Radiation.
**Question 29.**
*Explain why for cooking, a black vessel is more convenient than a polished one.*
**Answer:**
A black surface is a better absorber of heat.
**Question 30.**
*Heat is generated continuously in an electric heater, but its temperature becomes constant after some time. Why?*
**Answer:**
When the rate at which heat is generated by electric current becomes equal to the rate at which heat is lost by radiation, thermal equilibrium is reached, and hence temperature becomes constant.
**Question 31.**
*Why are ventilators placed near the roof in a room?*
**Answer:**
Warm air in the room becomes lighter and moves upward. So, for a better convection current, ventilators are placed near the roof of the room.
**Question 32.**
*Name three modes of the transfer of heat.*
**Answer:**
Conduction, convection, and radiation.
**Question 33.**
*Name the element that is the best conductor of heat?*
**Answer:**
Silver.
**Question 34.**
*What is the unit of the coefficient of thermal conductivity in SI?*
**Answer:**
Wm⁻¹ K⁻¹.
**Question 35.**
*What is thermal expansion?*
**Answer:**
The dimensions of all substances generally increase with an increase in temperature. This phenomenon is known as thermal expansion.
**Question 36.**
*Name the three types of expansion in solid?*
**Answer:**
The types of expansion in solids:
- Linear expansion
- Superficial expansion
- Volume expansion.
**Question 37.**
*Define the term ‘coefficient’ of linear expansion of solid.*
**Answer:**
Coefficient of linear expansion of solids: The coefficient of linear expansion of a solid is the increase in its length per unit length per degree rise of temperature.
**Question 38.**
*Give the SI unit of the
coefficient of linear expansion.*
**Answer:**
K⁻¹.
**Question 39.**
*Write the relationship among α, β, and γ.*
**Answer:**
α = β² = γ³.
**Question 40.**
*Does the unit of the coefficient of linear expansion depend on the unit of length?*
**Answer:**
No.
Certainly! Here's a more polished version:
### Short Answer Type Questions:
**Question 1.**
*What do you mean by heat?*
**Answer:**
Heat is a form of energy that produces the sensation of warmth.
**Question 2.**
*What are the different types of motion?*
**Answer:**
Different types of motions include:
- Translational motion
- Vibrational motion
- Rotational motion
**Question 3.**
*What is the definition of heat with respect to motion?*
**Answer:**
The definition of heat with respect to motion states that heat possessed by a body is the total thermal energy of the body, which is the sum of kinetic energies of all the individual molecules forming the body due to translational, vibrational, and rotational motions of the molecules.
**Question 4.**
*What do you mean by calorie?*
**Answer:**
A Calorie is the quantity of heat required to raise the temperature of 1 gram of water through 1°C.
**Question 5.**
*What is temperature?*
**Answer:**
Temperature is the thermal condition of a body that determines the direction of the flow of heat when the body is placed in thermal contact with another body.
**Question 6.**
*What is the upper fixed point of a thermometer?*
**Answer:**
The upper fixed point is the temperature of steam from water boiling under a pressure of 76 cm of mercury at sea level and 45° latitude.
**Question 7.**
*What is the lower fixed point of a thermometer?*
**Answer:**
The lower fixed point is the temperature of melting ice under a pressure of 76 cm of mercury at sea level and 45° latitude.
**Question 8.**
*What is the fundamental interval?*
**Answer:**
The fundamental interval is the difference between the fixed points of a scale.
**Question 9.**
*What do you mean by thermal expansion?*
**Answer:**
Thermal expansion is when the dimensions of all substances generally increase with an increase in temperature.
**Question 10.**
*What are the types of expansions in solids?*
**Answer:**
Types of expansions in solids include linear expansions, superficial expansions, and volume expansions.
**Question 11.**
*What is the apparent expansion of the liquid?*
**Answer:**
Apparent expansion of the liquid is when the expansion of the liquid is measured, ignoring the expansion.
**Question 12.**
*What is the real expansion of the liquid?*
**Answer:**
Real expansion of the liquid is when the actual expansion of the liquid is measured by considering the expansion of the containing vessel.
**Question 13.**
*What is the conclusion of Hope’s experiment?*
**Answer:**
The conclusion of Hope’s experiment is that water at the bottom, which is densest at 4°C, experiences a slightly lower temperature over time due to heat loss by conduction to the upper regions.
**Question 14.**
*What is molar specific heat at constant volume (Cv)?*
**Answer:**
Molar specific heat at constant volume (Cv) is the amount of heat required to raise the temperature of one mole of the gas through one degree, keeping the volume constant.
**Question 15.**
*What is molar specific heat at constant pressure (Cp)?*
**Answer:**
Molar specific heat at constant pressure (Cp) is the amount of heat required to raise the temperature of one mole of the gas through one degree, keeping the pressure constant.
**Question 16.**
*What is water equivalent of a body?*
**Answer:**
Water equivalent of a body is the mass of water which will be heated through one degree by the amount of heat that raises the temperature of the body through one degree.
**Question 17.**
*What is Regelation?*
**Answer:**
Regelation is the phenomenon of melting ice under pressure and freezing again on releasing the pressure.
**Question 18.**
*What do you mean by vapor pressure of a liquid?*
**Answer:**
Vapor pressure is the pressure exerted by a vapor when it evaporates at a specific temperature.
**Question 19.**
*What is conduction of heat?*
**Answer:**
Conduction is the process of the transfer of heat through a substance without any detectable motion of the particles of the substance.
**Question 20.**
*What is convection of heat?*
**Answer:**
Convection of heat is the process by which heat is transmitted through a liquid or gas from a hotter point to a colder point due to the bodily motion of the heated particles.
**Question 21.**
*What is radiation of heat?*
**Answer:**
Radiation is the transmission of heat from a hot body to a cold body without the help of any medium and without appreciable heating at the intervening medium, if any.
**Question 22.**
*What is a perfectly black body?*
**Answer:**
A perfectly black body is one that absorbs completely the radiations of all wavelengths incident upon it.
**Question 23.**
*What is the greenhouse effect?*
**Answer:**
The greenhouse effect is an example of selective absorption of heat by glass. The amount of heat transmitted through a substance depends on the temperature of the source of heat.
**Question 24.**
*What do you mean by global warming?*
**Answer:**
Global warming is the increase in Earth's average surface temperature due to the buildup of greenhouse gases in the atmosphere, leading to changes in climate patterns.
### Broad Answer Type Questions:
**Question 1.**
*State the units and dimensions of different coefficients.*
**Answer:**
The units and dimensions of different coefficients are essential in understanding the thermal properties of materials and substances. Here is a breakdown:
1. **Coefficient of Linear Expansion (α):**
- *Unit:* K⁻¹ (per degree Celsius or Kelvin)
- *Dimension:* [M⁰ L¹ T⁻² θ⁻¹]
2. **Coefficient of Superficial Expansion (β):**
- *Unit:* K⁻¹ (per degree Celsius or Kelvin)
- *Dimension:* [M⁰ L¹ T⁻² θ⁻¹]
3. **Coefficient of Volume Expansion (γ):**
- *Unit:* K⁻¹ (per degree Celsius or Kelvin)
- *Dimension:* [M⁰ L¹ T⁻² θ⁻¹]
4. **Specific Heat at Constant Volume (Cv):**
- *Unit:* J kg⁻¹ K⁻¹ (joules per kilogram per Kelvin)
- *Dimension:* [M¹ L² T⁻² θ⁻¹]
5. **Specific Heat at Constant Pressure (Cp):**
- *Unit:* J kg⁻¹ K⁻¹ (joules per kilogram per Kelvin)
- *Dimension:* [M¹ L² T⁻² θ⁻¹]
6. **Water Equivalent:**
- *Unit:* kg (kilograms)
- *Dimension:* [M¹ L⁰ T⁰ θ⁰]
These coefficients and specific heats play a crucial role in describing how a substance responds to changes in temperature and heat transfer.
