Specific latent heat.

When unit mass is involve in the conversion of matter from one state to another state then it is called specific latent heat of fusion and specific latent heat of vaporisation.

Specific latent heat of fusion

Specific latent heat of fusion is the quantity of heat energy require to convert unit mass of the substance from its solid state to its liquid state without any rise in temperature.

 Specific latent heat of vaporisation

This is the heat energy require to convert unit mass of the substance from its liquid sate to vapour state without any rise in temperature.

The unit of latent heat is joule, while the unit of specific latent heat is joule/kilogram

                Q=mL

Where Q is the quantity of heat or latent heat and L is the specific latent heat of fusion or vaporisaion.

Determination of specific latent heat of fusion of ice.

Dried ice is used in for this Experiment.

Calorimeter

The ice is dried and broke in to two equal parts. A thermometer is inserted in between the two parts and held firmly together . the temperature of the ice is recorded .

The  calorimeter with stirrer  is weigh and  half filled with warm water and  re-weigh.

The ice is then added to the warm water in the calorimeter  and stirred until all the ice melted. The final mass and temperature of the mixture is recorded.

Calculation

Let

 The temperature of the ice block =

The temperature of the warm water + calorimeter +stirrer =

The temperature of the final mixture =

The mass of the empty calorimeter + stirrer =

The mass of the empty calorimeter + stirrer + warm water =

The mass of the final mixture =

Specific heat capacity of the calorimeter =

Specific heat capacity of the water  =

Specific heat capacity of the ice  =

Specific Latent heat of fusion of ice = L

Heat gain = Heat loss

Heat gain = heat gain by ice from  to    + heat gain by the ice to melt + heat gain by the meltedice to rise from  to  

Heat loss =heat loss by the calorimeter +heat loss by the warm water

=

Therefore

Heat loss = heat gain

Therefore

Hence

PRECAUTION

1. USE A DRIED ICE
2. Make sure the calorimeter is properly lagged

Determination of specific  latent heat of vaporisation of steam.

Dried steam is used  for this experiment.

The steam is passed through a lagged tube into water inside calorimeter. The temperature of the steam is assumed to be temperature of boiling water.

The empty calorimeter with stirrer  is weigh and  half filled with  water then  re-weigh.

The steam is then added to the  water in the calorimeter  and stirred until the temperature  of the mixture rise significantly .The final mass and temperature of the mixture is recorded.

Calculation

Let

 The temperature of the steam = 

The temperature of the water  + calorimeter +stirrer =

The temperature of the final mixture =

The mass of the empty calorimeter + stirrer =

The mass of the empty calorimeter + stirrer +  water =

The mass of the final mixture =

Specific heat capacity of the calorimeter =

Specific heat capacity of the water  =

Specific Latent heat of vaporisation of steam = L

Heat gain = Heat loss

Heat loss = heat loss by the steam to condense to water at   + heat loss by condense  steam from   to   

Heat gain =heat gain by the calorimeter +heat gain by the  water

=

Therefore

Heat loss = Heat gain

=

Therefore,

Hence,

Precaution

1. The steam must be dried.
2. The calorimeter must be lagged.
3. The temperature of the final mixture  and the water should be  respectively. Where . For example if room temperature is   , x can be 7. The water will be   and final mixture   .
4. The mixture should be stirred continuously.

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