HEAT

      HEAT

There are mainly 4 scales of temperature :-

1. Kelvin(K)
2. Centigrade(*C)
3. Fahrenhiet(*F)
4. Reaumur(*r)

The relation between the following scales of temperature is as follows :

   *C -32 = K-273 = *F-32 = *r

         5           5              9        4

Heat energy is denoted by ‘Q’

Work is directly proportional to energy

So , W=JQ ( Here , J is the convergent factor whose value is equal to 4.18J/cal )

So we can also say that 1 cal = 4.18J

To test your understanding , here’s a small question :-

1. If the amount of work done by a body is 20.9J , find the amount of heat energy produced

ANSWER :- 

By formula , 

                         W=JQ

 20.9 = 4.18 * Q

Q = 20.9/4.19

Q=5 calories 

See , it’s that simple ! Now let’s move on

THE CONCEPT OF SPECIFIC HEAT 

Specific heat is denoted by ‘C’

Heat energy is directly proportional to the mass of the object -1

Heat energy is directly proportional to the temperature difference – 2

By 1 and 2 , 

Q = m.C.dtheta

Where m – Mass

             C – specific heat ( constant )

        dtheta – delta theta ( this denotes the temperature difference )

Magnitude of C of water – 1 

 Magnitude of C of ice – ½

LATENT HEAT

As you all must be aware , latent heat is the amount of heat energy which is required by a particle to change it’s physical state

Q = m.L

Where Q=Heat energy

              m = mass of the object

              L = Latent heat 

L of ice ---- 80 cal(By default)

The Challenger Question :-

Science is nothing without application , and if you’re not able to apply what you’ve just learnt , then there’s absolutely no point in learning

Here’s a question for you , it isn’t that tough if you use your common sense

QUESTION :-

Container A :- 100g Water at 100*C

Container B :- 100g Ice at -50*C

If the water kept in Container A is poured into Container B , calculate the amount of ice which will melt as a result of this

I can sense that you’re a bit baffled , so here’s the solution , now try to understand

ANSWER :-

Heat energy of water = m.C.dtheta

                                                           = 100 * 1 * 100

                                                           = 10000 calories 

                 Total heat energy of ice = m.c.dtheta + m.L

                                                            = 100 * ½ * 50 + 100*80

                                                            = 2500 cal + 8000 cal

Now what we have to see is , this latent heat ( 8000 cal ) will be responsible for melting the ice

But , this 2500 cal of heat energy will be responsible for bringing the temp. of ice to 0*C ( it’s quite obvious )

Only after the temperature reaches 0*C , the ice will start to melt 

Therefore , heat energy of water which will melt the ice   = total heat energy of water – heat energy required to lower the temperature of ice

               = 10000 – 2500

               = 7500g

So , % of ice melted = 7500/8000 * 100

                                    = 93.8%

                    This translates to 93.8g

FINAL ANSWER :- 93.8g of ice will melt

You must surely be happy today , because you’ve learnt something new

Stay tuned for more scientific information 

I hope you liked today’s topic

• Aryan Awasthi

Enjoy your high school with - High School Pedia : www.highschoolpedia.com

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