Important Notes for CBSE Class 6 Science Chapter 6 – Change around us. Change around us Class 6 Notes and Study Material Download in PDF form.
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Changes around us
There are many changes around us we see , some changes are slow some changes are fast .
Slow change:
There are many changes which are slow.
For example : plants growth , ripening of fruit , the Rustin of iron etc
Fast change:
There are many changes which are fast .
For example : the melting of ice , burning of matchstick , bursting of crackers etc.
Reversible changes :
Those change in which we can get the original substance back are called reversible changes .
Example : melting of ice , melting of chocolate etc.
Irreversible change :
Those substance in which we can not get the original substance back are called irreversible change.
Example:. Burning of wood , burning paper , ripening of fruit , food cooked etc.
Physical changes :
Those changes in which , change occurs in the physical properties of the substance are known as the physical changes.
Or
A change in which no new substance are formed and which can be reversed by reversing the condition are called physical changes.
Example : melting of solid , freezing of liquid , vaporization of liquid , etc.
Chemical changes :
Chemical changes occur when substance combine with another one to form one or more new substance .
Example : burning of materials ( wood , coal , paper , etc.) , Rusting , cooking food. Etc.
Contraction :
The process of becoming smaller , metal contract when they are cooled down and expand when they are hot.
Example : metal contract when Cooling.
Expansion :
The process becoming bigger. Metal expand when they are hot.
Example : metal expand when they get heat.
Evaporation :
The process of conversion of water into its vapour from at a temperature lower than its boiling point is called evaporation.
Melting :
The process conversion of substance from its solid form to its liquid form is known as melting.
Exothermic change :
A change in which heat is given out (that is evolved ) is called exothermic change.
Example : burning of substance given out heat.
Endothermic change :
A change in which heat is taken (that is absorbed) is called endothermic change.
Example : melting of substance.
Change around us Class 6 Notes