BOILING

Evaporation within the whole mass of liquid is called boiling. At which temperature boiling takes place is called boiling point.
Boiling point increases on adding impurity.
At 574.25 degree, the fahrenheit and kelvin scales read the same.

MELTING

The change of state from solid to liquid is known as melting. The temperature at which the solid and liquid states of the substances are in thermal equilibrium is called melting point.
The solid which expands on heating, their melting point increases with increase in pressure.
Melting point decreases on adding impurity.
Specific heat at boiling point and melting point is infinite.

SPECIFIC HEAT

The amount of heat required to raise the temperature of 1 g of a substance by 1 degree C is called the specific heat of gas.
It is represented by C. Its unit is cal/g degree C or joule/g degree C.

There are two specific heat of gases;

i) Specific heat at constant volume: At constant volume, the amount of heat required to raise the temperature of 1 g of a gas by 1 degree Celsius is called specific heat of constant volume.

ii) Specific heat at constant pressure : At constant pressure, the amount of heat required to raise the temperature of 1 g of a gas by 1 degree Celsius is called specific heat of constant pressure.

CALORIES

Amount of heat required to raise the temperature of 1 g of water by 1 degree C is called 1 cal or amount of heat required to raise the temperature of 1 g of water from 14.5 degree C to 15.5 degree C is called 1 calorie. It is also called international calorie.

1 calorie = 4.2 joule

MERCURY IS PREFERRED IN THERMOMETERS ?

Coefficient of real expansion of mercury is low and uniform.
- mercury has low specific heat.
- mercury does not wet the walls of capillary.
- mercury is a shining liquid and it can be obtained in pure form.
- thermal conductivity of mercury is low and its vapour pressure is also low.

GAS THERMOMETERS PREFERED TO LIQUID THERMOMETER ?

Gas thermometers are preferred over liquid thermometers because;

- gas expands more than liquid, hence gas thermometers are more sensitive than liquid thermometers.
- in a single thermometer different gases can be used.
- all the gases have same cubical expansion coefficient.
- little impurity in the gases has little effect on the temperature being measured.

TEMPERATURE RANGES OF DIFFERENT THERMOMETERS

i) Mercury thermometer from -30 degree C to 357 degree C.
ii) Gas thermometer from - 268 degree C to 1500 degree C.
iii) Platinum resistance thermometer - 200 degree C to 1200 degree C.
iv) Thermocouple thermometer -200 degree C to 1600 degree C.
v) The clinical thermometer reads from 96 degree F to 110 degree F.

TEMPERATURE SCALES

Some temperature scales are given as;

i) Centigrade Scale : In this scale, ice point and steam point are taken as 0 degree and 100 degree celsius. 1 degree celsius is equal to 100th part of difference between two points.

ii) Fahrenheit Scale : In this scale, ice point and steam point are taken as 32 degree and 212 degree F. 1 degree F is equal to 180th part of difference between two points.

iii) Kelvin Scale : In this scale, ice point and steam point are taken as 273 K and 373 K. 1 K is equal to 100th part of difference between two points.

iv) Rankie Scale : In this scale, ice point and steam point are taken as 460 degree Ra and 672 degree Ra. 1 degree Ra is equal to the 212th part of difference between two points.

v) Reaumur Scale : In this scale, ice point and steam point are taken as 0 degree R and 80 degree R. 1 degree R is equal to the 80th part of difference between two points.

HEAT AND ITS EFFECT

Heat is the form of energy. It is responsible for the change in thermal condition of the body. It may be defined as the energy flow due to a temperature difference.
The SI unit of heat is joule.
The practical unit of heat is calorie.
                            1 Calorie = 4.186 joule

ELASTIC LIMIT

The upper limit of the deforming force upto which, if deforming force is removed, the body regains its original form completely and beyond which if deforming force is increased, the body loses its property of elasticity and gets permanently deformed is called elastic limit.

IDEAL GASES

Practically, gases do not obey Boyle's, Charle's and pressure laws completely in all conditions of temperature and pressure. Ideal gas is that imaginary gas which obey Boyle's, charl;s and pressure law in all conditions.
Ideal gas equation is given by;

pV = RT

Where, R = universal constant


Characteristics of ideal gases;

- the size of the molecule of a gas is zero.
- there is no force of attraction or repulsion amongst the molecules of the gas.

KINETIC THEORY OF GASES

·         All the molecules of the gas are uniform, rigid and infinitely small, whose volume is negligible as compared to the volume of gas.

·         There is no force between gas molecules.

·         Collision between two molecules is perfectly elastic.

·         Density of molecules is uniform in the vessel.

·         The molecules can have all possible velocities.

·         Molecules move on a zig-zag way in any direction, this motion is called Brownian Motion.

·         The no.of molecules per unit volume of gas is constant.

ELASTIC LIMIT

The upper limit of a deforming force upto which, if deforming force is removed, the body regains its original form completely and beyond which if deforming force is increased , the body its property of elasticity and gets permanently deformed is called elastic limit.

STRAIN

The ratio of change in configuration produced in the body to the original configuration is called strain.
Strain is of three types;

Longitudinal Strain  change in length per unit original length

Volume Strain  change in volume per unit original volume

Shearing Strain  when there is change of shape of  a body without change in its volume, the strain produced is called shearing strain and is defined as the angle through which  a plane perpendicular to the fixed surface of the cubical body gets turned under the effect of tangential force.

STRESS

The restoring force acting on a unit surface area of object is called stress. Its unit is Newton per meter square.
                                     Stress = F/ A

The breaking force needed to break a wire is called tensile stress.
Ratio of the maximum load which the substance can bear and area of cross section is called breaking stress.

STOKE'S LAW

When a spherical body is dropped in a liquid, then the liquid applies a retarding force;
                           
                                          F = 6(pie)nrv

where, v = velocity of body
            r = radius of body
           n = coefficient of viscosity of liquid

TORRICELLI'S THEOREM

It is also known as velocity of efflux.
The word efflux means the outflow of liquid. According to torricelli's theorem, the velocity of efflux through an orifice at depth h from liquid surface is same as that of freely falling body from that height.

VISCOSITY

The property of liquids due to which they oppose the relative motion between their different layers is called viscosity.

BERNOULLI'S THEOREM

According to this theorem, "if a liquid is in a streamline motion, then at each point of its path, its total energy of unit volume i.e., sum of pressure energy, kinetic energy and potential energy is constant"

                               p + dgh + dv² / 2 = constant