.
2. Chemical Changes
These changes result in the formation of new substances. In a chemical change, the composition and molecular structure
of the substance undergoing changes are considered. e.g. When a piece of iron or nail is left in moist air for a
long time, it rusts and gives a reddish brown look. During rusting process iron combines with oxygen to give a new
product.
Here rusting, is a chemical change which cannot be reversed back by any physical process. As we eat food, the digestion of food starts trom the mouth and during this process many chemical changes take place in the stomach.
The complex food material gets converted into simple molecules of glucose which is oxidised in the body cells to release energy.
Similarly, burning of any substance is a chemical change. Burning is always accompanied by the production of heat.
Explosion of a fire work is also a chemical change (heat,light, sound and unpleasant gases are produced in explosion). Blue copper sulphate crystals on heating loses its all water molecules giving white anhydrous salt which decomposes into black cupric oxide and sulphur trioxide on strong heating.
Heat Strongly
CuSO4 •5H2O -->CuSO4-->CuO+SO3
Note
•Burning of a candle is an example of both physical and chemical changes.
•Ozone is decomposed to oxygen in the presence of ultraviolet rays. It is an example of chemical change.
Some facts about the chemical changes are
1•During chemical changes, the composition of the substance changes due to change in constituent particles of substance.
2. Identity of the substance is lost during a chemical change.
3• Energy is absorbed or released during a chemical change.
4•Chemical change is permanent and irreversible.
If you like our content then please share🏷️. And add your email id to get notification🔔
Tag
nda syllabus
atomic structure for nda
chemistry for nda
nda maths pdf
some important chemical compounds nda notes
defence guru
chemistry notes for cds
nda exam date
0 Comments