Question:
(a) What is evaporation ? State the various factors which affect evaporation.
Why does evaporation cool a liquid ?
Answer:
(a)When a liquid is left exposed to air, its volume decreases gradually. This is due to evaporation. In this process some of the liquid at the surface turns into vapour (or gas) and mixes with the gases in the air.Thus, when a liquid turns into vapour (or gas), it is said to evaporate. We can now define evaporation as follows : The process of a liquid changing into vapour (or gas) even below its boiling point is called evaporation.
The evaporation of a liquid depends mainly on the following factors :
(i)Temperature
(ii) Surface area
(iii) Humidity
(iv) Wind speed(b)The cooling caused by evaporation is based on the fact that when a liquid evaporates, it draws (or takes) the latent heat of vaporisation from 'anything' which it touches.
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.
Define the term Volatile Liquid.
Q 11.
Which state of matter is most easily compressible?
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.
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.
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.
Is smell of garlic or perfume a matter?
Q 37.
What is the general name of : (a) rigid form of matter ? (b) fluid forms of matter ?
Q 38.
The Kelvin temperature is 270 K. What is the corresponding Celsius scale temperature ?
Q 39.
Which of the following are matter?
Chair, Air, Love, Smell, Hate, Almonds, Thought, Cold, Cold drinks, Smell of perfume
Q 40.
Convert the following temperature to Celsius scale: (a) 300 K (b) 573 K
Q 41.
What are the conditions for 'something' to be called '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.
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 50.
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.
