Questions

Given Equation is 

Mg + O2 → MgO

Balancing the Chemical Equation is nothing but Conservation of Matter. As Matter is Neither created nor Destroyed, it must be conserved.

Here we have 1 Mg and 2 O on the left side and 1 Mg and 1 O on the right side

To balance that, add 1 Mg on the left side so that it becomes 2 Mg and 2 O on the left side

i.e,

2 Mg + O2 → 2 MgO

Here it has 2 Mg & 2 O on the left side and 2 Mg and 2 O on the right side and the Chemical equation is Balanced.

The Upanishads are a part of the Vedas and are ancient Sanskrit texts that contain some of the central philosophical concepts and ideas of Hinduism, some of which are shared with Buddhism, and Jainism.

The Upanishads are commonly referred to as Vedanta in the history of India.

Nuclear sizes are expressed in a unit called "Fermi" which is a unit of length equal to 10⁻¹⁵ metre (one femtometre), used in nuclear physics. It is similar to the diameter of a proton.

The point or place of origin of an earthquake is called Focus. 

And,

The point where the seismic waves reach the surface is called as Epicenter.

A) Cooking of Food  ------ Chemical Change

B) Digestion of Food ----- Chemical Change

C) Freezing of water ----- Physical Change

D) Water is heated up ---- Physical Change

because here the chemical composition of the substance changes in A & B only.

Since we know that, If the chemical composition is changing then it is a chemical change and if the chemical composition is remaining the same, then it is a physical change.