Question:
What causes evaporation?
OR
Explain evaporation and its cooling effect in terms of kinetic energy of particles.
Answer:
During evaporation, the molecules which possess higher kinetic energy leave the liquid and go into space above the liquid as vapours. The remaining molecules possessing lower kinetic energy are left in the liquid state. Consequently, the average kinetic energy decreases which result in the fall of temperature of the liquid.
Matter in Our Surroundings
Q 1.
What is SI unit of temperature? Give mathematical relation also.
Q 3.
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 do you mean by the term Volume?
Q 8.
Why solids cannot be compressed like gases?
Q 9.
What are the ways a gas can be liquefied?
Q 10.
Define the term Volatile Liquid.
Q 11.
Define transpiration.
Q 12.
Which state of matter is most easily compressible?
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.
Our own bodies contain examples of all three states of matter. Can you identify these?
Q 19.
Why is light not considered matter?
Q 20.
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 21.
Define Latent Heat of Fusion and Latent Heat of vaporisation.
Q 22.
How can matter change its state?
Q 23.
How matter is classified in terms of composition?
Q 24.
Why do gases diffuse rapidly?
Q 25.
Why do diffusion become faster at higher temperatures?
Q 26.
Which of the following state does not exist at room temperature conditions: a) Solids b) Liquids c) Gas d) Plasma
Q 27.
What is the physical state of water at the following temperatures? (a) 25 °C (b) 0 °C (c) 100 °C
Q 28.
How vapour is different from gases? Give examples of each.
Q 29.
In which case evaporation of water will be faster i.e. near the sea or far away from the sea.
Q 30.
Name the process by which a drop of ink spreads in a beaker of water.
Q 31.
Convert the temperature of 373°C to the Kelvin scale.
Q 32.
What is the (a) common unit of temperature, and (b) SI unit of temperature ?
Q 33.
Give the usual name for the following :Heat required to change the state of a substance without changing the temperature.
Q 34.
Why do solids expand a bit on heating and contract a bit on cooling?
Q 35.
What causes evaporation?
OR
Explain evaporation and its cooling effect in terms of kinetic energy of particles.
Q 36.
What is the general name of : (a) rigid form of matter ? (b) fluid forms of matter ?
Q 37.
Write the full forms of the following :(a) LPG (b) CNG
Q 38.
The Kelvin temperature is 270 K. What is the corresponding Celsius scale temperature ?
Q 39.
Give reasons for the following observations. The smell of hot sizzling food reaches you several meters away, but to get smell from cold food you have to go close.
Q 40.
Give reasons to justify: (a) Water at room temperature is a liquid. (b) An iron almirah is solid.
Q 41.
Why does the temperature of a substance remain constant during melting and boiling even when heat is being supplied to it continuously?
Q 42.
Honey is more viscous than water. Can you suggest why ?
Q 43.
Convert the temperature of 573 K to the Celsius scale.
Q 44.
(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.
Q 45.
Which of the following are matter?
Chair, Air, Love, Smell, Hate, Almonds, Thought, Cold, Cold drinks, Smell of perfume
Q 46.
A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Q 47.
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 48.
What factors affect the rate of evaporation?
Q 49.
Is smell of garlic or perfume a matter?
Q 50.
What are the conditions for 'something' to be called 'matter' ?
