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    Distinguish between physical and chemical changes

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    Talib Al_Munawri
    Director-General
    Director-General

    Posts : 337
    Join date : 2009-07-03
    Age : 30
    Location : Sultanate of Oman

    Distinguish between physical and chemical changes

    Post by Talib Al_Munawri on Fri Sep 11, 2009 11:09 pm

    Distinguish between physical and chemical changes



    Physical change


    Physical change is any change in a substance that does not involve a change in its chemical composition

    During a physical change, no new chemical bonds are formed, and so the chemical composition remains the same.

    Many physical properties can be observed using our senses; color, crystal shape, and phase at room temperature are some examples.

    Other physical properties involve quantitative observations are density, specific heat capacity, boiling, freezing, expanding, and dissolving.

    Phase changes are physical changes, if they are caused by heating or cooling. If you take some water and you heat it up and it changes to gas, that is a physical change. You still have water, only now it is steam instead of liquid.

    Also included in physical changes due to color change is by mixing or by diluting a material or, in some cases, even by heating. For example, if you turn on an electric range and the element gets hot, you can see a color change. That is also a physical change.

    Physical changes can be reversible or irreversible.


    Chemical changes



    Chemical changes occur whenever there is a rearrangement of atoms that makes or breaks chemical bonds.

    Chemical changes are that which we see the change in the condition of the material or from a change in what materials are present.

    A chemical change is one in which the substance is transformed to a new substance. That is, there is a change in the chemical composition of the substance.

    During a chemical change, the atoms are pulled apart from one another, rearranged, and put back in a new arrangement. Examples of chemical change are burning, rusting, fermenting, and decomposing.

    Chemical changes can be reversible or irreversible
    E.g., NaOH(aq) + HCl(aq) H2O(l) + NaCl(aq)


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