Question:
Define Latent Heat of Fusion and Latent Heat of vaporisation.
Answer:
The latent heat of fusion of a substance is the quantity of heat required to convert one unit mass of the substance from solid state to the liquid state at its melting point without any change of temperature. The quantity of heat required to convert one unit mass of a liquid into vapour at its boiling point without any change of temperature is called its latent heat of vaporisation. [Another better definition provided by one of our read Mr. Saheel Deshpande is as follows:] Latent heat of vaporisation: It is the amount of heat consumed when 1 kg of liquid changes into vapor at constant temperature and pressure.
Matter in Our Surroundings
Q 1.
What is SI unit of temperature? Give mathematical relation also.
Q 3.
What do you mean by change in state?
Q 4.
How matter is classified in terms of physical state?
Q 5.
What are the ways a gas can be liquefied?
Q 6.
Which state of matter is most easily compressible?
Q 7.
What is evaporation? Why does evaporation cause cooling?
Q 8.
Define the term Volatile Liquid.
Q 9.
What do you mean by the term Volume?
Q 10.
List any five physical properties of liquids.
Q 11.
Why solids cannot be compressed like gases?
Q 12.
Define transpiration.
Q 13.
Arrange the following substances in increasing order of intermolecular force of attraction: water, sugar, oxygen
Q 15.
The mass per unit volume of a substance is called density (density=mass/volume). Arrange the following in order of increasing density:
Air, Exhaust from chimneys, Honey, Water, Chalk, Cotton and Iron.
Q 16.
What are the differences between boiling and evaporation?
Q 17.
What do you mean by the following terms:
a. Evaporation
b. Sublimation
c. Condensation
Q 18.
Define evaporation.
Q 19.
Define Latent Heat of Fusion and Latent Heat of vaporisation.
Q 20.
Our own bodies contain examples of all three states of matter. Can you identify these?
Q 21.
How matter is classified in terms of composition?
Q 22.
Why is light not considered matter?
Q 23.
How can matter change its state?
Q 24.
How vapour is different from gases? Give examples of each.
Q 25.
Why do diffusion become faster at higher temperatures?
Q 26.
In which case evaporation of water will be faster i.e. near the sea or far away from the sea.
Q 27.
Which of the following state does not exist at room temperature conditions: a) Solids b) Liquids c) Gas d) Plasma
Q 28.
What is the physical state of water at the following temperatures? (a) 25 °C (b) 0 °C (c) 100 °C
Q 29.
Which of the following are matter?
Chair, Air, Love, Smell, Hate, Almonds, Thought, Cold, Cold drinks, Smell of perfume
Q 30.
Why do gases diffuse rapidly?
Q 31.
Convert the following temperature to Celsius scale: (a) 300 K (b) 573 K
Q 32.
Why does the temperature of a substance remain constant during melting and boiling even when heat is being supplied to it continuously?
Q 33.
Explain compressibility in gases with an example?
Q 34.
Name the process by which a drop of ink spreads in a beaker of water.
Q 35.
Why is ice at 273 K more effective in cooling than water at the same temperature?
Q 36.
What factors affect the rate of evaporation?
Q 37.
Convert the temperature of 373°C to the Kelvin scale.
Q 38.
What are the characteristics of matter?
Q 39.
The Kelvin temperature is 270 K. What is the corresponding Celsius scale temperature ?
Q 40.
The Kelvin scale temperature is 0 K. What is the corresponding Celsius scale temperature ?
Q 41.
Define the following terms:
a. Melting point
b. Freezing point
c. Boiling point
Q 42.
Convert the following temperatures:
a. -78.0 °C to Kelvins
b. 775 K to °C
c. 489 K to °C
d. 24 °C to kelvins
Q 43.
What causes evaporation?
OR
Explain evaporation and its cooling effect in terms of kinetic energy of particles.
Q 44.
The mass per unit volume of a substance is called density.(density = mass/volume). Arrange the following in order of increasing density – air, exhaust from chimneys, honey, water, chalk, cotton and iron.
Q 45.
Give the usual name for the following :Heat required to change the state of a substance without changing the temperature.
Q 46.
State whether the following statement is true or false : Solid carbon dioxide is stored under low pressure.
Q 47.
Explain with an experiment to show gases do not have fixed shape or volume.
Q 48.
Why do solids expand a bit on heating and contract a bit on cooling?
Q 49.
The boiling point of water is 100°C. Express this in SI units (Kelvin scale).
Q 50.
Name one common substance which can be easily changed from one state to another by heating or cooling.
