Two changes are described below.

Water vapor condenses.
Liquid water separates into hydrogen and oxygen.

Which statement is true about the two changes?
Both are chemical changes because new substances are formed.
Both are physical changes because only the physical state of the substances change.
A is a physical change due to a change of state, but B is a chemical change because new molecules are formed.
A is a chemical change due to a change of state, but B is a physical change because new molecules are formed.

A is a physical change due to a change of state, but B is a chemical change because new molecules are formed.

Explanation:

Physical Change                                                                                              

The changes that occur only due to change in shape or physical properties but their chemical or internal composition remain unchanged.  

These changes were reversible.

They have same chemical property.

These changes can be observed with naked eye.

Example :

Water vapors condenses.

Water converting to Ice

Water converting to gas

In this water molecule remain the same only they rearrange themselves that change its state of mater not composition

Chemical change:

The changes, that occur due to change in the composition of a substance and result in a different compound is known as chemical change.

These changes are irreversible

These changes occur due to chemical reactions

These may not be observed with naked eye

Example:

Combustion of fuel or wood: that oil or wood convert into energy, CO2 and ash in case of wood

Boiling of egg: that change the chemical composition of protein in the egg .

The reaction of decomposition of water into Hydrogen and oxygen:

2H₂O →  2H₂ + O₂

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