Matter in Our Surroundings Class 9 MCQ With Answers Set-3
Q21. Which of the following is NOT a property of latent heat of fusion?
A. It is the amount of heat required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point.
B. It is a constant value for a given substance.
C. It is used to overcome the forces of attraction between the particles.
D. It is a measure of the temperature of the substance
Answer – D. It is a measure of the temperature of the substance.
Explanation-The latent heat of fusion is not a measure of the temperature of the substance. It is the amount of heat required to change the state of the substance, without changing its temperature.
Q22. Which of the following substances has the highest latent heat of fusion?
A. Water
B. Ice
C. Mercury
D. Nitrogen
Answer – A. Water
Explanation-Water has the highest latent heat of fusion of all substances. This is why it takes a lot of heat to melt ice.
Q23. Why does the temperature of the system not change after the melting point is reached, till all the ice melts?
A. Because the heat is being used to overcome the forces of attraction between the particles.
B. Because the heat is being stored in the liquid.
C. Because the heat is being released into the surroundings.
D. All of the above
Answer – A. Because the heat is being used to overcome the forces of attraction between the particles.
Explanation-Heat is being used to overcome the forces of attraction between the particles, which is why the temperature of the system does not change.
Q24. What is the latent heat of the fusion of water?
A. 334 kJ/kg
B. 373 K
C. 273 K
D. 100 °C
Answer – A. 334 kJ/kg
Explanation-The latent heat of fusion of water is 334 kJ/kg. This means that it takes 334 kJ of heat energy to melt 1 kg of ice at 0 °C.
Q25. Which of the following is NOT a property of latent heat of vaporization?
A. It is the amount of heat required to change 1 kg of a liquid into a gas at atmospheric pressure at its boiling point.
B. It is a constant value for a given substance.
C. It is used to overcome the forces of attraction between the particles.
D. It is a measure of the temperature of the substance
Answer – D. It is a measure of the temperature of the substance.
Explanation-The latent heat of vaporization is not a measure of the temperature of the substance. It is the amount of heat required to change the state of the substance, without changing its temperature.
Q26. Which of the following substances has the highest latent heat of vaporization?
A. Water
B. Ice
C. Mercury
D. Nitrogen
Answer – A. Water
Explanation-Water has the highest latent heat of vaporization of all substances. This is why it takes a lot of heat to boil water.
Q27. Why does the temperature of the system not change after the boiling point is reached, till all the water boils?
A. Because the heat is being used to overcome the forces of attraction between the particles.
B. Because the heat is being stored in the gas.
C. Because the heat is being released into the surroundings.
D. All of the above
Answer –A. Because the heat is being used to overcome the forces of attraction between the particles.
Explanation-Heat is being used to overcome the forces of attraction between the particles, which is why the temperature of the system does not change.
Q28. What is the latent heat of the vaporization of water?
A. 2260 kJ/kg
B. 373 K
C. 273 K
D. 100 °C
Answer – A. 2260 kJ/kg
Explanation-The latent heat of vaporization of water is 2260 kJ/kg. This means that it takes 2260 kJ of heat energy to vaporize 1 kg of water at 100 °C.
Q29. What is the SI unit of temperature?
A. Celsius
B. Fahrenheit
C. Kelvin
D. All of the above
Answer – C. Kelvin
Explanation-The SI unit of temperature is Kelvin.
Q30. What is the conversion formula between Kelvin and Celsius scales?
A. K = °C + 273.15
B. °C = K – 273.15
C. Both A. and (B)
D. None of the above
Answer – C. Both A. and B
Explanation-The conversion formula between Kelvin and Celsius scales is K = °C + 273.15 or °C = K – 273.15.
