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.
Which state of matter is most easily compressible?
Q 7.
What do you mean by the term Volume?
Q 8.
Define the term Volatile Liquid.
Q 9.
What is evaporation? Why does evaporation cause cooling?
Q 10.
List any five physical properties of liquids.
Q 11.
Arrange the following substances in increasing order of intermolecular force of attraction: water, sugar, oxygen
Q 12.
Why solids cannot be compressed like gases?
Q 13.
Define transpiration.
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.
How matter is classified in terms of composition?
Q 18.
Our own bodies contain examples of all three states of matter. Can you identify these?
Q 19.
Define evaporation.
Q 20.
What do you mean by the following terms:
a. Evaporation
b. Sublimation
c. Condensation
Q 21.
Define Latent Heat of Fusion and Latent Heat of vaporisation.
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.
What is the physical state of water at the following temperatures? (a) 25 °C (b) 0 °C (c) 100 °C
Q 28.
Which of the following state does not exist at room temperature conditions: a) Solids b) Liquids c) Gas d) Plasma
Q 29.
Which of the following are matter?
Chair, Air, Love, Smell, Hate, Almonds, Thought, Cold, Cold drinks, Smell of perfume
Q 30.
Convert the following temperature to Celsius scale: (a) 300 K (b) 573 K
Q 31.
Why does the temperature of a substance remain constant during melting and boiling even when heat is being supplied to it continuously?
Q 32.
Why do gases diffuse rapidly?
Q 33.
Explain compressibility in gases with an example?
Q 34.
Why is ice at 273 K more effective in cooling than water at the same temperature?
Q 35.
What factors affect the rate of evaporation?
Q 36.
The Kelvin scale temperature is 0 K. What is the corresponding Celsius scale temperature ?
Q 37.
Name the process by which a drop of ink spreads in a beaker of water.
Q 38.
Define the following terms:
a. Melting point
b. Freezing point
c. Boiling point
Q 39.
State whether the following statement is true or false : Solid carbon dioxide is stored under low pressure.
Q 40.
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 41.
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 42.
The Kelvin temperature is 270 K. What is the corresponding Celsius scale temperature ?
Q 43.
Explain with an experiment to show gases do not have fixed shape or volume.
Q 44.
Honey is more viscous than water. Can you suggest why ?
Q 45.
Convert the temperature of 373°C to the Kelvin scale.
Q 46.
Write the relation between Kelvin scale and Celsius scale of temperature.
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.
Why do solids expand a bit on heating and contract a bit on cooling?
Q 49.
What is the scientific name of particles which make up matter ?
Q 50.
The boiling point of water is 100°C. Express this in SI units (Kelvin scale).
