Tag: change of states

Questions Related to change of states

On increasing the external pressure , the boiling point of liquid 

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

  1. is raised

  2. is lowered

  3. remain unaffected

  4. uncertain

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Correct Option: A
Explanation:
On increasing the external pressure, the boiling point of liquid is increased.
Boiling point is the temperature at which vapor pressure of the liquid equals to the external pressure.
V.P, of liquid is a function of temperature.
Now, if we increase the external pressure, a higher temperature would be required so that V.P. equals to external pressure.

Rice takes longest time to cook

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

  1. at sea level

  2. at shimla

  3. at Mount Everest

  4. in a submarine 100 m below the surface of sea

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Correct Option: C
Explanation:

At higher altitude, water starts boiling at lower temperature and heat required for cooking food is not available, because heat escapes in form of water vapour. So, rice takes longer time to cook at Mount Everest

Temperature at which liquid changes to gaseous state

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

  1. Freezing point

  2. Boiling point

  3. Neutral state

  4. None

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Correct Option: B
Explanation:

boiling point is a temperature state when liquid state starts charging into gaseous state.

When 1 g of ice melts at $0^\circ C$

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

  1. 80 cal of heat is liberaed

  2. 80 cal of heat is absorbed

  3. no heat is required

  4. 160 cal heat is absorbed

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Correct Option: B
Explanation:
For melting of $1g$ of ice $80cal$ of heat is required.
As latent heat of fusion for water is the heat required or released when $1g$ of ice melts into water or water changes into ice.

Latent heat of fusion for water $=80cal/g$

A piece of ice at $0$ is put into a vessel containing water at $0$ . The ice will

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

  1. melt

  2. not melt

  3. slightly melt

  4. vanish in no time

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Correct Option: B
Explanation:
A piece of ice at $0^oC$ is put into a vessel containing water at $0^oC$ ice will not melt.
The ice will not melt because no heat will transfer as there is no temperature difference. And without that heat transfer is impossible.

Melting point of Aluminium is:

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

  1. $1000\ ^\circ C$

  2. $659\ ^\circ C$

  3. $1500\ ^\circ C$

  4. $100\ ^\circ C$

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Correct Option: B
Explanation:

Melting point of Aluminium is $660.3^oC \approx (659^oC)$

Which of the following is true regarding a bucket of boiling water and a cup of boiling water.
I.The temperature of the two is the same.
II.The heat content of the two is the same.
III. The bucket of water contains more heat and is therefore hotter

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

  1. I only

  2. II only

  3. I and III only

  4. II and III only

  5. I, II and III only

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Correct Option: A
Explanation:

The water is boiling In bucket and in cup, we have same liquid in bucket and cup, the water ,since the boiling point of water is  $100^{o}C$ therefore temperature is same in both .

The heat given $\Delta Q$ to the mass $m$  of substance to raise the temperature by $\Delta \theta$  is 
                          $\Delta Q=mc\Delta\theta$    where  $c$  is the specific heat of substance
The mass of water in bucket is larger therefore it has larger heat content by above relation. 
               now        $\Delta\theta=\Delta Q/mc$ 
The bucket of water contains more heat but on the other hand it also has larger mass ,therefore $\Delta Q/m$ is constant for both and hence both are at same temperature  
                          $\Delta\theta=\Delta Q/mc$ 
 here, $c$ is constant because both pots have same liquid (water) .

In pressure cookers the boiling point of water increases due to the __________  created by blocking of the steam by weight.

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

  1. temperature

  2. moisture

  3. heat

  4. pressure

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Correct Option: D
Explanation:

The boiling point of any liquid increases by exerting pressure on it. In a pressure cooker, the whistle applies pressure because of its weight.

The melting point of ice can be given by:

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

  1. $32\ ^\circ F$

  2. $32 \ ^\circ C$

  3. $273.15\ K$

  4. Both a and c

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Correct Option: D
Explanation:

The relation between Celsius and Fahrenheit is given by $\dfrac C{100} = \dfrac{F - 32} {180}$ 

The relation between Celsius and Kelvin is given by, $K = C + 273.15$
So, melting point of ice $=0^oC=32^oF=273.15K$

Boiling point of water at normal atmospheric pressure is ______.

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

  1. $0^{\circ}C$

  2. $100^{\circ}C$

  3. $110^{\circ}C$

  4. $-4^{\circ}C$

Show answer
Correct Option: B
Explanation:

The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid. The boiling point of liquids varies with and depends upon the surrounding environmental pressure. 

The normal boiling of a liquid is the special case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level i.e., at 1 atmosphere (atm) is $100^0C$.