Question:
What is evaporation? Why does evaporation cause cooling?
Answer:
The process in which a liquid change into its vapour state at temperatures below the boiling point is called evaporation. Evaporation is an endothermic process i.e. liquid absorbs heat during evaporation. This heat may be provided either by the surroundings or by liquid itself. When the evaporating liquid takes the required heat from other parts of the liquid, the rest of the liquid cools down. On the other hand, if the liquid takes heat from the surroundings, it causes cooling of the surroundings. E.g. on a hot day (sunny day), we perspire. When this sweat evaporates, it absorbs the required heat from our body, and we feel cool.
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 3.
What do you mean by change in state?
Q 5.
What is evaporation? Why does evaporation cause cooling?
Q 6.
List any five physical properties of liquids.
Q 7.
Which state of matter is most easily compressible?
Q 8.
What are the ways a gas can be liquefied?
Q 9.
What do you mean by the term Volume?
Q 10.
Define the term Volatile Liquid.
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.
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.
Define Latent Heat of Fusion and Latent Heat of vaporisation.
Q 21.
Why is light not considered matter?
Q 22.
How can matter change its state?
Q 23.
How matter is classified in terms of composition?
Q 24.
How vapour is different from gases? Give examples of each.
Q 25.
Why do diffusion become faster at higher temperatures?
Q 26.
Why do gases diffuse rapidly?
Q 27.
In which case evaporation of water will be faster i.e. near the sea or far away from the sea.
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 state does not exist at room temperature conditions: a) Solids b) Liquids c) Gas d) Plasma
Q 30.
Convert the temperature of 373°C to the Kelvin scale.
Q 31.
Write the full forms of the following :(a) LPG (b) CNG
Q 32.
What is the (a) common unit of temperature, and (b) SI unit of temperature ?
Q 33.
Which of the following are matter?
Chair, Air, Love, Smell, Hate, Almonds, Thought, Cold, Cold drinks, Smell of perfume
Q 34.
Convert the following temperature to Celsius scale: (a) 300 K (b) 573 K
Q 35.
Convert the temperature of 573 K to the Celsius scale.
Q 36.
Why does the temperature of a substance remain constant during melting and boiling even when heat is being supplied to it continuously?
Q 37.
Name the process by which a drop of ink spreads in a beaker of water.
Q 38.
What are the conditions for 'something' to be called 'matter' ?
Q 39.
The Kelvin scale temperature is 0 K. What is the corresponding Celsius scale temperature ?
Q 40.
What causes evaporation?
OR
Explain evaporation and its cooling effect in terms of kinetic energy of particles.
Q 41.
What factors affect the rate of evaporation?
Q 42.
Give the usual name for the following :Heat required to change the state of a substance without changing the temperature.
Q 43.
Write the relation between Kelvin scale and Celsius scale of temperature.
Q 44.
What is meant by saying that the latent heat of vaporisation of water is 22.5 x
Q 45.
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 46.
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 47.
The Kelvin temperature is 270 K. What is the corresponding Celsius scale temperature ?
Q 48.
Define the following terms:
a. Melting point
b. Freezing point
c. Boiling point
Q 49.
What is the general name of : (a) rigid form of matter ? (b) fluid forms of matter ?
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.
