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.
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.
What is evaporation? Why does evaporation cause cooling?
Q 7.
List any five physical properties of liquids.
Q 8.
Which state of matter is most easily compressible?
Q 9.
Define the term Volatile Liquid.
Q 10.
What do you mean by the term Volume?
Q 11.
Define transpiration.
Q 12.
Why solids cannot be compressed like gases?
Q 13.
Arrange the following substances in increasing order of intermolecular force of attraction: water, sugar, oxygen
Q 15.
What are the differences between boiling and evaporation?
Q 16.
Define 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.
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.
Why is light not considered matter?
Q 22.
How matter is classified in terms of composition?
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.
Which of the following state does not exist at room temperature conditions: a) Solids b) Liquids c) Gas d) Plasma
Q 27.
In which case evaporation of water will be faster i.e. near the sea or far away from the sea.
Q 28.
Why do gases diffuse rapidly?
Q 29.
What is the physical state of water at the following temperatures? (a) 25 °C (b) 0 °C (c) 100 °C
Q 30.
Which of the following are matter?
Chair, Air, Love, Smell, Hate, Almonds, Thought, Cold, Cold drinks, Smell of perfume
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.
Convert the temperature of 373°C to the Kelvin scale.
Q 34.
What is the (a) common unit of temperature, and (b) SI unit of temperature ?
Q 35.
What is meant by saying that the latent heat of vaporisation of water is 22.5 x
Q 36.
Name the process by which a drop of ink spreads in a beaker of water.
Q 37.
State whether the following statement is true or false : Solid carbon dioxide is stored under low pressure.
Q 38.
Convert the temperature of 573 K to the Celsius scale.
Q 39.
What are the conditions for 'something' to be called 'matter' ?
Q 40.
What is the general name of : (a) rigid form of matter ? (b) fluid forms of matter ?
Q 41.
Write the full forms of the following :(a) LPG (b) CNG
Q 42.
What is the scientific name of particles which make up matter ?
Q 43.
Honey is more viscous than water. Can you suggest why ?
Q 44.
The Kelvin scale temperature is 0 K. What is the corresponding Celsius scale temperature ?
Q 45.
Give the usual name for the following :Heat required to change the state of a substance without changing the temperature.
Q 46.
(a) What is evaporation ? State the various factors which affect evaporation.
Why does evaporation cool a liquid ?
Q 47.
What are the characteristics of matter?
Q 48.
The Kelvin temperature is 270 K. What is the corresponding Celsius scale temperature ?
Q 49.
Define the following terms:
a. Melting point
b. Freezing point
c. Boiling point
Q 50.
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.
