Evaporation

Q. If the intermolecular forces vanish away, the volume occupied by the molecules contained in $4.5\text{kg}$ water at STP will be

1. $11.2{\text{m}}^3$
2. $5.6\text{litres}$
3. $4.5{\text{m}}^3$
4. $5.6{\text{m}}^3$

Q. A projectile is projected with velocity of $25\text{m/s}$ at an angle $\theta$ with the horizontal. After $t$ seconds its inclination with horizontal becomes zero. If $R$ represents horizontal range of the projectile, the value of $\theta$ will be
[use $g=10{\text{m/s}}^2$]

1. ${\tan }^{-1}\left[\frac{4t^2}{5R}\right]$
2. $\frac{1}{2}{\sin }^{-1}\left[\frac{5t^2}{4R}\right]$
3. ${\cot }^{-1}\left[\frac{R}{20t^2}\right]$
4. $\frac{1}{2}{\sin }^{-1}\left[\frac{4R}{5t^2}\right]$

Q. The velocity $-$ time graph of a body moving along a straight line is as follows: The displacement of the body in $5s$ is

1. $2m$
2. $4m$
3. $5m$
4. $3m$

Q. State whether the following diagram depicts ideal gas behaviour or not?

A)
B)
C)

Q.

A child running a temperature of 101°F is given an antipyrin (i.e. a medicine that lowers fever) which causes an increase in the rate of evaporation of sweat from his body. If the fever is brought down to 98 °F in 20 min, what is the average rate of extra evaporation caused, by the drug? Assume the evaporation mechanism to be the only way by which heat is lost. The mass of the child is 30 kg. The specific heat of human body is approximately the same as that of water, and latent heat of evaporation of water at that temperature is about 580 cal g^–1.

Q.

Give reason why?

Particles of matter move more rapidly on the application of heat.

Q.

Look at Figure and suggest in which of the vessels A, B, C, or D the rate of evaporation will be the highest? Explain.

Moving Fan A B C

Q.

Give reasons why wet clothes are spread on the clothes line for faster drying.

Q. A child runing a temperature of $101{}^{\circ }F$ is given an antipyrin (i.e. a madicine that lowers fever) which causes an increase in the rate of evaporation of sweat from his body. If the fever is brought down to $98{}^{\circ }F\text{in}20\text{minutes},$ what is the average rate of extra evaporation caused, by the drug.Assume the evaporation mechanism to be the only way by which heat is lost. The mass of the child is $30kg.$ The specific heat of human body is approximately the same as that of water, and latent heat of evaporation of water at that temperature is about $580cal/g$

Q.

The rate of evaporation is inversely proportional to which of the following quantities?

1. The speed of wind

2. Temperature

3. Surface area

4. Humidity

Q. Evaporation takes place at all temperatures.

1. True
2. False

Q. Explain, why dogs pant during hot summer days using the concept of evaporation?

Q. From the following which are the factors affecting the rate of evaporation?

1. Temperature
2. Exposed Surface Area
3. Humidity
4. All of the above

Q.

Evaporation causes cooling. Justify this statement by citing a suitable example.

Q. Explain the statement
Sugar crystals dissolve faster in hot water than cold water.

Q. If humidity is high in the atmosphere, rate of evaporation is higher.

1. True
2. False

Q.

Why do wet clothes dry fast on a windy day?

Q. If the intermolecular forces vanish away, the volume occupied by the molecules contained in $4.5\text{kg}$ water at STP will be

1. $5.6{\text{m}}^3$
2. $4.5{\text{m}}^3$
3. $11.2{\text{m}}^3$
4. $5.6\text{litres}$

Q. The larger the exposed surface area, lower is the rate of evaporation.

1. True
2. False

Q.

State two factors on which rate of evaporation depends upon.

Q.

Statement 1: Evaporation causes cooling of the liquid

Statement 2: During evaporation, the surface molecules with high kinetic energy get evaporated.

1. Statement 2 is correct and Statement 1 is wrong.
2. Statement 1 and Statement 2 both are correct and statement 2 is not the correct explanation of statement 1.
3. Statement 1 and Statement 2 both are correct and Statement 2 is correct explanation of Statement 1.
4. Statement 1 is correct and Statement 2 is wrong.

Q.

Assertion(A): A balloon filled with air and tightly tied, when hung close to the source of heat, bursts after some time.

Reason (R): The pressure exerted by the gas is inversely proportional to the temperature of the gas.

1. Both A and R are true and R is the correct explanation of A.

2. Both A and R are true, but R is not the correct explanation of A.

3. A is true and R is false.

4. A is false and R is true.

Q. The rate of evaporation of a given liquid depends only on the surface area of the liquid exposed to air.

1. True
2. False

Q.

Give two points of differences between evaporation and boiling.

Q.

A, B, C and D are volatile liquids.
The order of volatility is
A > C > B > D
Now, at a particular temperature:

1. Vapour pressure of A >Vapour Pressure of D
2. Vapour pressure of C >Vapour pressure of B
3. Vapour pressure of B <Vapour pressure of D
4. Vapour pressure of A >Vapour pressure of B

Q. Does the substance absorb or liberate any heat energy during the change of phase ?

Q.

Statement 1: Evaporation causes cooling of the liquid

Statement 2: During evaporation, the surface molecules with high kinetic energy get evaporated.

1. Statement 1 and Statement 2 both are correct and Statement 2 is correct explanation of Statement 1.
2. Statement 1 and Statement 2 both are correct and statement 2 is not the correct explanation of statement 1.
3. Statement 1 is correct and Statement 2 is wrong.
4. Statement 2 is correct and Statement 1 is wrong.

Q. The process in which no heat enters or leaves the system is termed as :

1. isochoric
2. isobaric
3. isothermal
4. adiabatic

Q. Why vegetables are cooked with difficulty at a hill station?

1. Boiling point decreases as we go up on hilly areas
2. Boiling point increases as we go up on hilly areas
3. Boiling point increases because atmospheric pressure is low
4. There is no change in boiling point (change the option)

Q. Why skin feels dry in an air-conditioned room?

1. Because the rate of evaporation decreases with lower humidity.
2. Because the rate of evaporation increases with lower humidity.
3. Because the rate of evaporation remains same with lower humidity.
4. Because the rate of evaporation increases with higher humidity.