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Physical and Chemical Changes

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For every change that we get to see around us, there’s either a change in composition or change in shape and size of the reactants. These attributes to both physical and chemical change. If the changes that take place is irreversible then it is considered to be chemical in nature while the physical change covers only the change in shape or size but not the actual composition.

Moreover, the change is considered to be permanent in case we are looking at chemical change. The physical change doesn’t take that into account and we do get back the original form.

Characteristic of the Physical Change

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Characteristics of physical change might cover only the physical aspect and not the chemical nature or composition. The tearing of paper is physical although the original size of the page might not be available but the paper still remains paper. There is no change as far the chemical composition is concerned. 

Now if we burn the same piece of paper then we get to see black carbon and that definitely is chemical change. So physical change is something that we always get back the original form or there is no such changes in chemical composition. The chemical change whereas doesn’t take into account of whether there’s change in size or shape as the main concern is about the irreversible process that a chemical change goes through.

Physical change has no timeline and definitely depends upon the physical dynamics which the substance goes through. Breaking of chair, cutting of paper with scissors or tearing of cloth. Everything depends upon how these activities are done. A chemical change can be very fast, slow or release and absorb heat energy from the surrounding. So it can be either combustion or respiration type of chemical reaction. It can also be exothermic like reaction between glycerine and water. It can be endothermic reaction if vinegar is mixed with water. 

Examples of Physical Change

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There are many changes which we consider under physical changes and are known to almost everyone who can understand the minute details of such changes. There are some unconventional changes which can be attributed for only physical change. 
  • Zinc metal when heated turns golden yellow but turns back to white powder after it cools down
  • Iron piece heated at high temperature turns orange or bright red and then turns back to original colour when cooled down.
  • Metals when heated begins to melt and reshaped to other forms 

Characteristic of Chemical Change

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Any change which goes through a permanent change and brings about a change which is irreversible can be categorised as chemical change. Chemical changes bring about change in colour or physical attributes but these are irreversible.

Chemical changes can be very fast or very slow. Chemical changes can also bring about change in heat capacity within the system or in the surroundings. Chemical composition or the rearrangement of atomic combinations also takes place and helps in creating newer products after the chemical change has gone through.

Examples of Chemical Change

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Burning of sugar molecules or charring of sugar into pure carbon. Slow chemical process like respiration brings about complete change in compositions but goes through a slow deliberate process. Some chemical process bring about change in luminosity in the system or its immediate surroundings. 

Chemical change always bring about in chemical composition but it may or may not bring about physical changes as well. Evolution of gas or appearance of bubbles on metal piece or appearance of blisters on metal surface are all specific characteristics of chemical change.  

Physical Change Vs Chemical Change

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Physical change  Chemical change 
There is no timeline for such changes  These are either very slow or fast depending upon the reactants
Changes are always temporary Changes are permanent 
There is no change in heat of the system Always accompanying change in heat, either in surrounding of system or within the system
Only physical attributes are taken into account  Both chemical and physical attributes are taken into consideration