Tag: force and kinetic theory

Questions Related to force and kinetic theory

If, melting and boiling point of a liquid is $-{50}^{o}C$ and ${150}^{o}C$ respectively, and on the basis of this liquid a thermometer is formed with ${0}^{o}L$ representing the melting point as the minimum temperature on the scale and ${100}^{o}L$ representing the boiling point as the maximum temperature on the scale, find the melting and boiling point on this thermometer

physics the kinetic model of matter force and kinetic theory change of states phase change

  1. $0$ and ${100}^{o}L$ respectively

  2. ${30}^{o}L$ and ${80}^{o}L$ respectively

  3. ${20}^{o}L$ and ${70}^{o}L$ respectively

  4. ${25}^{o}L$ and ${75}^{o}L$ respectively

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Correct Option: D

A constant pressure air thermometer gave a reading of 47.5 units of volume when immersed in ice cold water, and 67 units in a boiling liquids. The boiling point of the liquid will be

physics the kinetic model of matter force and kinetic theory change of states phase change

  1. $135^{0}$C

  2. $125^{0}$C

  3. $112^{0}$C

  4. $100^{0}$C

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Correct Option: A

Freezing mixture is a mixture which produces very low temperature. State whether true or false.

physics the kinetic model of matter force and kinetic theory change of states phase change

  1. True

  2. False

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Correct Option: A
Explanation:
Freezing mixture is a mixture which produces very low temperature. Statement is true.
Because it is a mixture of ice, water and salt or dry ice or alcohol which produces very low temperature.

Boiling is a surface phenomenon.

physics the kinetic model of matter force and kinetic theory change of states phase change

  1. True

  2. False

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Correct Option: B
Explanation:
The statement is false, boiling is a surface phenomenon.
Actually, boiling is a bulk a phenomenon. Heat energy goes to the entire bulk of liquid and it starts boiling. Whereas evaporation is a surface phenomenon

When salt is properly mixed with ice, then melting point of ice 

physics the kinetic model of matter force and kinetic theory change of states phase change

  1. is lowered

  2. remains the same

  3. is raised

  4. becomes infinite

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Correct Option: A
Explanation:
When salt is mixed with ice, then melting point of ice is lowered.
This is the fact due to which salt is used to melt ice on the rod in winter.

Fill in the blanks :

The ........................... of water is defined as the constant temperature at which water changes to steam.

physics the kinetic model of matter force and kinetic theory change of states phase change

  1. melting point

  2. boiling point

  3. saturation point

  4. all of the above

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Correct Option: B
Explanation:

Answer is B

The constant temperature at which a liquid boils and turns to vapour is known as boiling point.

Boiling of liquid can take place at any temperature. 

physics the kinetic model of matter force and kinetic theory change of states phase change

  1. True

  2. False

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Correct Option: B
Explanation:

The boiling point of a liquid is the temperature at which its vapor pressure is equal to the pressure of the gas above it.

Vaporization takes place at all temperatures.

The saturated vapour pressure of water at $100^\circ C$ is

physics the kinetic model of matter force and kinetic theory change of states phase change

  1. 750 mm of Hg

  2. 760 mm of Hg

  3. 76 mm of Hg

  4. 7.6 cm of Hg

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Correct Option: B
Explanation:

Vapour pressure or equilibrium vapour pressure or saturated vapour pressure is defined as the pressure exerted by a vapour in thermodynamic equilibrium with condensed phase at given temperature. At $100^oC$, the vapour pressure is $1atm$; i.e. 760mm of Hg i.e. 76cm of Hg as $1mm=10^{-1}cm$.

The water can be made to boil even at $0$ if the pressure of surrounding is:

physics the kinetic model of matter force and kinetic theory change of states phase change

  1. 56 cm of Hg

  2. 5 cm of Hg

  3. 0.1 cm of Hg

  4. 4.6 mm of Hg

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Correct Option: A
Explanation:
The water can be made to boil even at $0^\circ C$. 
As we know, the ideal equation for gases is $pV=nRT$. Now, if $V$ and $n$ are taken constants, $p=cT$, where $c$ is a constant.
So pressure is directly proportional to the temperature.
Water boils at $100^\circ C$ or $373K$ at $1atm$ pressure. So, to obtain boiling at $0^\circ C$ or $273K$, you need to reduce the pressure to $\dfrac {273\times 1}{373} atm = 0.732 atm=56\text{cm of Hg}$(approx).

When 1 g of water at $100^\circ C$ gets converted into steam at the same temperature, the change in volume is approximately

physics the kinetic model of matter force and kinetic theory change of states phase change

  1. 1 cc

  2. 1000 cc

  3. 1500 cc

  4. 1670 cc

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Correct Option: D
Explanation:

During change of state mass does not change.

Mass of water = 1gm
So mass of steam is also= 1gm
Density of steam =$0.0006gm/cm^3$
Initail volume of water =1$cm^3$(Density =$1gm/cm^3$) ($1=\dfrac { 1 }{ V } $) $,v=1cm^3$
Later volume of water converted to steam =$\dfrac { mass\quad of\quad steam }{ Density\quad of\quad steam } $
$=\dfrac { 1 }{ 0.0006 } $
$=\dfrac { 10000 }{ 6 } { cm }^{ 3 }$
$= 1670cm^3$
Change of volume = $1670cm^3$