Physics
Assertion (A) : We often pour tea in a saucer to cool it faster.
Reason (R) : Evaporation takes place at all temperatures.
- Both A and R are true and R is the correct explanation of A
- Both A and R are true and R is not the correct explanation of A
- Assertion is true but reason is false
- Assertion is false but reason is true
Matter
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Answer
Both A and R are true and R is not the correct explanation of A
Explanation
Assertion (A) is true because the rate of evaporation increases if the area of surface exposed increases so pouring tea into a saucer increases the surface area, which enhances evaporation, allowing the tea to cool more quickly.
Reason (R) is true because evaporation is a surface phenomenon which occurs at any temperature, not just at the boiling point.
But here reason does not explain the assertion.
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Related Questions
Boiling takes place from
- from the surface of the liquid
- throughout the liquid
- from mid-portion of liquid
- from none of the above
Identify the correct statement.
(1) The molecules of water move faster than ice.
(2) The molecules are more closely packed in ice than water.
(3) The molecules of water vibrate to and fro only but those of ice are free to move within the boundary of the vessel in which it is kept.
(4) The molecules have more intermolecular space in ice than in water.
- (1), (2) and (3)
- (2), (3) and (4)
- (1) and (2)
- all are correct
Assertion (A) : The molecules in a liquid can move within the boundary of the vessel.
Reason (R) : A liquid has a definite volume and a definite shape.
- Both A and R are true and R is the correct explanation of A
- Both A and R are true and R is not the correct explanation of A
- Assertion is true but reason is false
- Assertion is false but reason is true
Fill in the blanks:
(a) Evaporation takes place at …………… temperatures.
(b) …………… process is just the reverse of melting.
(c) …………… is a process that involves direct conversion of a solid into its vapour on heating.
(d) The temperature at which a solid converts into a liquid is called its …………… .
(e) The smallest unit of matter that exists freely in nature is called …………… .
(f) Molecules of a substance are always in a state of …………… and so they possess …………… .
(g) Inter-molecular space is maximum in …………… less in …………… and the least in …………… .
(h) Inter-molecular force of attraction is maximum in …………… , less in …………… and the least in …………… .