# Calorimetry And Thermal Expansion - 1

Calorimetry And Thermal Expansion

Introduction

Calorimetry can be considered to be the earliest known principal of Heat and Thermodynamics.This was the introduction of the widely used principal of Conservation of Energy to mankind.

Thermal Expansion too find a great importance in engineering application.

Its knowledge should also be imported for efficient working of various machines.

__Calorimetry and Thermas Expansion__:-

__Calorimetry__:-__Heat__:-

It is a form of energy which determines the change in thermas state of a body.

Heat flows from a body which has a higher temp. to the body which has lower temp.

__Specific Heat__:- Quantity of heat in calories required to raise the temp. of 1 gm. of that substance by 1C.

__thermal Equilibrium__:- Two or move bodies an said to be in then mal equilibrium with each other if threr is no folow of heat from one body to other when they are brought in contact with each other.

__Zenoth Law of Thermobodynamics and Temperature [Secondary Information]__:-

If system A is in thermal equilibrium with system B and system B is in thermal equilibrium with system C, then system A and C are in equilibrium with each other.

__Dum Question__:-

Q. Why iron becomes hot in sunlight?

A. Heat flows from surroundings to iron. (high to lower temerrantance).

__Temperature__:- It is digree of hotness or coldness of body.

__Measurement of Temprature [ Secondary Information]__:- Temprature of a system is measured indivectly making use of the fact that cutain physical quantities of substance change with temperatire.

For eg, On celsius scale lo and l

_{100}denote the length of the mercury at 0C and 100C resp.

We have

Similarly

Where R

_{0}, R

_{T}, R

_{100}denote electrical resistance at 0

^{0}C, 100

^{0}C, resp.

__Triple Point[ Secondary Information]__:- Unique set of pressure and temp. Exist at which are these states (solid, liquid and vapones) of a pure substance can exist orace in equilibrium. This temprature is called triple point of substance.

__Kelvin Scale__:

The celsius scale i9s defined such as

T (K) = T (^{0}C) + 273.15 |

__Dum Question__:-

Q. Some physical quantities change due to change in temp. Name a few.

A. Pressure, Volume, length, etc.

Q. The pressure of pure water is P at triple point. Temperature is increased to its boiling point. Pressure changes. What is the Changes.

A. Pressuer increases.

__Illustration__:

Q. When a block metal of specific heat 0.1 cal/g/

^{0}C and weighing 110 gm. is heated to 100

^{0}C and then quickly transfered to a colarimeter containing 200 gm. if a liquid at 10

^{0}C, the resulting temprature is 18

^{0}C. On repeating the experiment with 400 gm. of same luquid in the same calorimeter at same initial temp., the resulting temp. is 14.5

^{0}C. Find:

(a) Sp. heat of the liquid.

(b) The water equivalent of calorimeter.

Ans.

Heat lost by the block = Heat gained by (liquid + calorimeter)

110 X 0.1 X (100 - 18) = 200 X S X (18 - 10) + W X (18 - 10)

1600S + 8W = 902

Heat lost by the block = Heat gained by (liquid + Container)

110 X 0.1 X (100 - 14.5) = 400 X S X (14.5 - 10) + W X (14.5 X10)

1800S + 14.5W = 940.5

S = 0.45 cal/g/C and W = 16.6 gm.

__Thermal Expension__:- When a solid is heated, its length, surface area and the volume increases.

__Line as Expansion__:

Consider a lod of length l

_{1}at a temp. T

_{1}- Let it be heated to a temp t

_{2}and increased length of the rod be l

_{2}, then

l_{2} = l_{1}(1 + |

: T

_{2}- T

_{1}

[ Secondary Information]

We have dl l>br /> and dl d

dl = ld

__Superficial Expansion (Expansion of sunface)__:-

If A

_{1}is the area of solid at T

_{1}and A

_{2}si the area at T

_{2 }, then

A_{2} = A_{1} (1 + ) |

= Coefficient of superficial (Oval) Expansion