• Molarity (M) can be defined as the ratio of number of moles of solute to the volume of solution in liter.
• It can also be defined as the number of moles of solute present in unit litre or cubic decimeter of solution.
• It is function of temperature due to the dependence of volume on temperature whereas Mass %, ppm, mole fraction and molality are independent of temperature because mass does not depend on temperature.
• Mathematically, Molarity = Moles of Solute / Volume of Solution in Litre

Law of conservation of Mass

This is a principle used in analysis of chemical reactions.

• A chemical reaction is basically a rearrangement of atoms among different molecules.
• If the total binding energy of the reacting molecules is less than the total binding energy of the product molecules, the difference appears as heat and the reaction is exothermic.
• The opposite is true for energy absorbing (endothermic) reactions.
• Since the atoms are merely rearranged but not destroyed, the total mass of the reactants is the same as the total mass of the products in a chemical reaction.
• Mass is related to energy through Einstein theory,

E = mc², c – speed of light in vacuum

A British archaeologist Howard Carter discovered Tut’s tomb in 1922. Carter worked for months. He carefully recorded Tut’s treasures. Then he began investigating his three nested coffins. He found a shroud adorned with garlands of willow, olive and lotus leaves. Perhaps Tut was buried in March or April. Carter ran into trouble when he reached the mummy. The ritual resin had hardened. It cemented Tut to the bottom of his solid gold coffin. No amount of force could separate them. Then Carter tried another way of loosening the resins. He placed the mummy in the blazing sunshine. But the move didn’t work. At last, he decided to cut the mummy free from the resins. The resins had to be chiselled away beneath the limbs and the trunk. In his defence, Carter had little choice. Had he not cut the mummy free, thieves would have run away with the gold.

• Dalton’s law of partial pressure states that the total pressure of a mixture of ideal gases is the sum of partial pressures.
• Consider if there are several ideal gases mixed together in a vessel,then the total pressure of that vessel is equal to sum of partial pressure.
• Partial pressure is the pressure exerted by a particular gas if only that gas is present in the vessel.
• For example: -
  • Consider if in a vessel there is a mixture of 3 gases, A,B and C.So the partial pressure of A is equal to pressure exerted only by Aand considering B and C are not present.
  • Similarly partial pressure of B is equal to the pressure exerted only by B and considering A and C are not there.
  • Similarly for C.
• According to Dalton’s law the total pressure of mixture is sum of partial pressure of A, partial pressure of B and partial pressure of C.

Coefficient of kinetic friction is a well known word in physics. When an object is in motion, the resisting force will try to stop the motion of the object. The friction occurs between the two surfaces when they are in motion relatively to each other. The friction force between the surfaces transforms the kinetic energy into heat energy. From the coefficient of friction, the idea of the roughness of the surface can be determined.

To measure the frictional force, coefficient of friction is used. There are three types of coefficient of frictions i.e. coefficient of kinetic friction, coefficient of static friction and coefficient of rolling friction.

Here, the topic is coefficient of kinetic friction. The expression for the coefficient of kinetic friction is,

Here,  is the kinetic friction force,  is the coefficient of kinetic friction and  is the normal force acting on the object.

Thus, the coefficient of friction between the two surfaces can be defined as the ratio of the frictional force between the object and the surface to the normal force action on the object.

The coefficient of kinetic friction has no unit as the coefficient of kinetic friction is the ratio of two forces.

When the coefficient of friction value is high, the stopping distance of the moving object will become less. On the other hand, if the coefficient of friction value is low, the stopping distance of the moving object will become high.