Class - 6
Subject - Science
Chapter - 6
Change around us
Many changes are taking place around us on their own.In this field, the crop change from time to time.
Sometimes, leaves fall from trees, change colour and dry out. The flower bloom and then wither away.
** Some change can be reversed an some cannot be reversed.
** A change may occur by heating a substance or bye mixing it with some other.
Types of change
(1) Reversible change :- A change in which the initial substance can be obtained back by reversing the action.
Ex. Folding of paper, dissolving sugar in water.
(2) Irreversible change :- Change in which the initial substance cannot be obtained back by reversing the action.
Ex. Burning of paper, grinding grains etc.
(3) physical change :- Change in the form of substance but not in chemical identity. No new substance formed. Change is some time reversible.
Ex. Breaking a log of wood.
(4) Chemical change :- Change in which substance is transformed into new substance. Initial substance is lost.Change is always irreversible.
Ex. Burning a log of wood.
Boiling :- The rapid vaporization of a liquid when it is heated to its boiling point.
Condensation :- The change of water vapour into liquid water on cooling.
Freezing :- The process in which a liquid turns into solid when its temperature is lowered.
Melting :- The process in which a solid converts into a liquid by applying heat.
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