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    Changing the state of a substance

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    Talib Al_Munawri
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    Changing the state of a substance

    Post by Talib Al_Munawri on Fri Sep 11, 2009 10:18 pm

    Changing the state of a substance


    The three states are dependent on temperature and pressure. If you were to heat a solid, it might melt
    or vaporize. A liquid could boil. If a gas is cooled enough, it will liquify;
    and if a liquid is cooled enough, it will freeze into a solid, but small changes
    do not have much effect on the state of the phase, but the change occurs abruptly
    when the temperature and pressure exceeds a certain amount.

    Temperature

    Heating and cooling can change the kinetic energy of the particles in a substance, and so, we can change the physical state of a substance by heating or cooling it.

    Cooling a gas may change the state to a liquid

    Cooling a liquid may change the state to a solid


    Pressure

    Increasing the pressure on a substance forces the molecules closer together, which increases the strength of intermolecular forces

    Increasing the pressure on a gas may change the state to a liquid

    Increasing the pressure on a liquid may change the state to a solid



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    Color

    is another very important property of material. If something is red, it's red;
    and if it's blue, it's blue. The color that we see is actually a combination
    of many different colors.

    Newton did an important experiment with light. He ran white light through a
    prism and broke it up into a full spectrum with all the colors in the rainbow.
    Rainbows themselves are white light that has been broken up into a variety of
    different colors, the component colors of white light. Things we see that are
    white are able to reflect all colors that hit them. Whereas something that is
    red can either be red because it absorbs green and reflects everything else or
    it might absorb everything but red and reflect only the red. So, there are a
    variety of different aspects to the colors.



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    Clarity

    is another property having to do with appearance. Something is clear or
    transparent if light can pass through it. If you can see through it, it is clear.
    A material can be clear whether or not it has color. For example you can have
    a clear blue sky. The sky does have color, so don't confuse the term "clear"
    with the term "colorless".

    If only a limited amount of light will pass through something, like waxed paper
    or frosted glass, it is called translucent. If no light will pass through the
    object, it is called opaque.


    Homogeneity:

    Another important aspect of the appearance of a material is whether the material is homogeneous or heterogeneous. The term “phase” is used to describe composition of properties. A homogeneous mixture consists single phase. A heterogeneous mixture consists two or more phases.

    Materials which have the same appearance all the way through the sample are said to be homogeneous. Homogenized milk, for example, is the same all the way through it does not have separate layers of milk and cream.

    On the other hand, a material which has visibly distinguishable components
    is said to be heterogeneous. Dirt or concrete or seawater would be fairly
    good examples of heterogeneous materials. On reasonably close inspection,
    each of these materials contains within it a variety of distinguishable
    components.

      Current date/time is Tue Oct 24, 2017 12:50 pm