Tag: phase change

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Questions Related to phase change

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

On increasing the external pressure , the boiling point of liquid 

  1. is raised

  2. is lowered

  3. remain unaffected

  4. uncertain
Reveal answer Fill a bubble to check yourself
A Correct answer
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.
Multiple choice physics the kinetic model of matter force and kinetic theory change of states phase change

Rice takes longest time to cook

  1. at sea level

  2. at shimla

  3. at Mount Everest

  4. in a submarine 100 m below the surface of sea
Reveal answer Fill a bubble to check yourself
C Correct answer
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

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

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

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $=80cal/g$
Multiple choice physics the kinetic model of matter force and kinetic theory change of states phase change

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

  1. melt

  2. not melt

  3. slightly melt

  4. vanish in no time
Reveal answer Fill a bubble to check yourself
B Correct answer
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.
Multiple choice physics the kinetic model of matter force and kinetic theory change of states phase change

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

  1. I only

  2. II only

  3. I and III only

  4. II and III only

  5. I, II and III only
Reveal answer Fill a bubble to check yourself
A Correct answer
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) .

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

Boiling point of water at normal atmospheric pressure is ______.

  1. $0^{\circ}C$

  2. $100^{\circ}C$

  3. $110^{\circ}C$

  4. $-4^{\circ}C$
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $100^0C$.