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 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.
List any five physical properties of liquids.
Q 7.
Which state of matter is most easily compressible?
Q 8.
What is evaporation? Why does evaporation cause cooling?
Q 9.
Define the term Volatile Liquid.
Q 10.
What do you mean by the term Volume?
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 14.
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.
Why is light not considered matter?
Q 21.
How matter is classified in terms of composition?
Q 22.
Our own bodies contain examples of all three states of matter. Can you identify these?
Q 23.
How can matter change its state?
Q 24.
How vapour is different from gases? Give examples of each.
Q 25.
In which case evaporation of water will be faster i.e. near the sea or far away from the sea.
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.
Why do diffusion become faster at higher temperatures?
Q 29.
Why do gases diffuse rapidly?
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.
What factors affect the rate of evaporation?
Q 34.
Name the process by which a drop of ink spreads in a beaker of water.
Q 35.
Convert the temperature of 373°C to the Kelvin scale.
Q 36.
What is the (a) common unit of temperature, and (b) SI unit of temperature ?
Q 37.
State whether the following statement is true or false : Solid carbon dioxide is stored under low pressure.
Q 38.
What causes evaporation?
OR
Explain evaporation and its cooling effect in terms of kinetic energy of particles.
Q 39.
Write the full forms of the following :(a) LPG (b) CNG
Q 40.
Honey is more viscous than water. Can you suggest why ?
Q 41.
Convert the temperature of 573 K to the Celsius scale.
Q 42.
The Kelvin scale temperature is 0 K. What is the corresponding Celsius scale temperature ?
Q 43.
What is the scientific name of particles which make up matter ?
Q 44.
Write the relation between Kelvin scale and Celsius scale of temperature.
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.
Is smell of garlic or perfume a matter?
Q 47.
What are the conditions for 'something' to be called 'matter' ?
Q 48.
The boiling point of water is 100°C. Express this in SI units (Kelvin scale).
Q 49.
What is meant by saying that the latent heat of vaporisation of water is 22.5 x
Q 50.
What are the characteristics of matter?
