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  • 19 August 2018

    NCERT STD 6 SCIENCE UNIT 6 CHANGES AROUND US UNIT TEST PDF FILE

    In our day to day life, you will observe many changes around us. Day changes into night and night in day, you can observe a sudden change in weather, the flowering of plants, milk changing into curd etc. In this article, we will discuss Chapter 6 Changes around us from Class 6 Science.
    A change can bring different kinds of effect on the things around us. Some of the effects brought are permanent in nature which cannot be reversed. Some effects are brought into position, shape, size or state of the things; these effects are temporary in nature.
    Changes caused by heating
    Some objects simply get hot, but no other change takes place – When we drink hot milk or coffee, from a cup, we feel that the cup is hot. Although it doesn’t change the state of the cup take place.
    Some objects get hot and expand – The metal gets heated and increase in size, on cooling the metal got contracted and regained its original size.
    Some objects get hot and burn – If we will burn a candle it will heat and melt away, this change is irreversible in nature as we cannot get the candle back in shape.
    Some objects change their state When ice is heated it changes into water, when water is heated it changes into steam. These changes can be easily reversed hence they are called reversible changes.
    Changes caused by Pressure or Force
    When you fill air into a balloon, by applying pressure to your lungs, the shape and size of the balloon changes. If we continue filling more air, then a stage will come when the balloon bursts and its shape changes again. The tube within the tyre changes its shape and fits completely.

    Changes caused by dissolving
    During the process of dissolving a change is brought in the soluble substance.
    Reversible and irreversible changes
    A change which can be reversed by removing the cause is called reversible change. In this change, the products formed can be converted back into their originals forms.
    E.g :- Water can be changed into ice by placing it in the freezing chamber of the fridge. The ice so formed can be converted back into the water by placing the ice outside the fridge.
    A change which cannot be reversed even by removing the cause is called an irreversible change. In this change, the products cannot be converted back into their original form.
    E.g :- When a paper is burnt it changes into ash and smoke. Ash and smoke cannot be converted into paper again.

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    By Nikunj Savani

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