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 2.
How matter is classified in terms of physical state?
Q 4.
What do you mean by change in state?
Q 5.
List any five physical properties of liquids.
Q 6.
What is evaporation? Why does evaporation cause cooling?
Q 7.
What are the ways a gas can be liquefied?
Q 8.
What do you mean by the term Volume?
Q 9.
Why solids cannot be compressed like gases?
Q 10.
Which state of matter is most easily compressible?
Q 11.
Define the term Volatile Liquid.
Q 12.
Define transpiration.
Q 13.
Arrange the following substances in increasing order of intermolecular force of attraction: water, sugar, oxygen
Q 15.
Define evaporation.
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.
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 19.
Our own bodies contain examples of all three states of matter. Can you identify these?
Q 20.
Why is light not considered matter?
Q 21.
Define Latent Heat of Fusion and Latent Heat of vaporisation.
Q 22.
How can matter change its state?
Q 23.
Why do gases diffuse rapidly?
Q 24.
How matter is classified in terms of composition?
Q 25.
Why do diffusion become faster at higher temperatures?
Q 26.
How vapour is different from gases? Give examples of each.
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.
In which case evaporation of water will be faster i.e. near the sea or far away from the sea.
Q 30.
Convert the temperature of 373°C to the Kelvin scale.
Q 31.
Name the process by which a drop of ink spreads in a beaker of water.
Q 32.
What is the (a) common unit of temperature, and (b) SI unit of temperature ?
Q 33.
What causes evaporation?
OR
Explain evaporation and its cooling effect in terms of kinetic energy of particles.
Q 34.
Why do solids expand a bit on heating and contract a bit on cooling?
Q 35.
Give the usual name for the following :Heat required to change the state of a substance without changing the temperature.
Q 36.
The Kelvin temperature is 270 K. What is the corresponding Celsius scale temperature ?
Q 37.
Which of the following are matter?
Chair, Air, Love, Smell, Hate, Almonds, Thought, Cold, Cold drinks, Smell of perfume
Q 38.
Convert the following temperature to Celsius scale: (a) 300 K (b) 573 K
Q 39.
Is smell of garlic or perfume a matter?
Q 40.
What are the conditions for 'something' to be called 'matter' ?
Q 41.
What is the general name of : (a) rigid form of matter ? (b) fluid forms of matter ?
Q 42.
Write the full forms of the following :(a) LPG (b) CNG
Q 43.
Write the relation between Kelvin scale and Celsius scale of temperature.
Q 44.
Why does the temperature of a substance remain constant during melting and boiling even when heat is being supplied to it continuously?
Q 45.
The boiling point of water is 100°C. Express this in SI units (Kelvin scale).
Q 46.
Convert the temperature of 573 K to the Celsius scale.
Q 47.
The Kelvin scale temperature is 0 K. What is the corresponding Celsius scale temperature ?
Q 48.
A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Q 49.
Honey is more viscous than water. Can you suggest why ?
Q 50.
(a) Define the term 'latent heat of vaporisation' of a liquid. What is the value of the latent heat of vaporisation of water ?
(b) Draw a labelled diagram of the experimental set-up to study the latent heat of vaporisation of water.
