Why is the heat given at the time of change of state called latent heat?

Ans: – As when the more heated or the object has more temperature is transfer from this object to the other. And always this happens because of trend of the transferring of high temperature to low temperature.

 

A certain amount of water is heated at a constant rate. The time to bring it to boiling is t1 and the time required from beginning of boiling to boiling off the whole amount is t2. Which is greater t1or t2? Why?

Ans: – We all know that time in heating the object at certain temperature at starting is law as compared to the final temperature where the liquid gets boiled.

 

At what temperature the numerical value of temperature on Fahrenheit scale will be double the value on Celsius scale.

Ans: – We know, C/5=F-32/9.

Let, c=x  and  F=2x,

So, x/5=2x -32/9;

Or, x= 160℃.

The value in Fahrenheit scale is 320℃.

 

A 50 cm silver bar shortens by 1.0 mm when cooled. How much was it cooled?

(Given: – coefficient of linear expansion of silver = 18 × 10-6 per degree Celsius)

Ans: –

 

 

 

 

 

 

 

 

 

How much heat energy is required to change 200 g of ice at –20°C to water at 70°C?

(Given: Latent heat of fusion of ice = 335 kJ kg–1, and specific heat of ice =2100 J kg–1 °C–1, specific heat of water = 4.2 kJ kg–1 °C–1)

Ans: –