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Physical and Chemical Changes Test - 12

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Physical and Chemical Changes Test - 12
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Weekly Quiz Competition
  • Question 1
    1 / -0
    Changes in which one or more new substances are formed are called _______ changes.
    Solution
    Changes in which one or more new substances are formed are called chemical changes.
    Example: Sugar undergoes a chemical change when it is cooked to make caramel.
    Option A is correct.
  • Question 2
    1 / -0
    Growth of plants is a:
    Solution
    The growth of plants is a chemical change, as its growth can not be reverted. And there are many chemical reactions such as photosynthesis which contribute to the growth of the plant.
    Hence, option B is correct.
  • Question 3
    1 / -0

    A change in which the form of matter is altered but one substance is not transformed into another is called:

    Solution
    A physical change is a change of the physical state. They are usually reversible. The physical properties of a substance include such characteristics as shape (volume and size), color, texture, flexibility, density, and mass.

    Hence, we can say a change in which the form of matter is altered but one substance is not transformed into another is called a physical change.

    Therefore, option A is correct.
  • Question 4
    1 / -0
    For rusting of iron to take place, ________ are required.
    Solution
    The rusting of Iron requires iron, water, and oxygen.

    First step: Oxidation of solid iron
    Dissolution of solid iron into solution
    $$ Fe(s)\rightarrow Fe^{2+}(aq) + 2e^{-} $$

    $$ 4e^{-} + 4H^{+} (aq) + O_2(aq)\rightarrow 2H_2O(l)$$

    Second step: Formation of hydrated iron oxide(rust)
    iron dissolves a predominance of hydroxide ions in the water to form green rust.
    $$ Fe^{2+} (aq) + 2OH^{-}(aq)\rightarrow Fe(OH)_2(s)$$

    $$ 4Fe^{2+} (aq) + 4H^{+} (aq) + O_2(aq)\rightarrow 4Fe^{3+} (aq) + 2H_2O(l)$$

    The overall reaction is written as:
    $$ 4Fe + 3O_2 + 6H_2O\rightarrow 4Fe(OH)_3$$

    This compound dehydrates to become $$Fe_2O_3.H_2O$$ (chemical formula for rust).


  • Question 5
    1 / -0
    Magnetization of an iron piece is a:
    Solution
    The magnetization of iron occurs due to the temporary alignment of the electrons present in it in one direction only. This is done by rubbing the north pole of the magnet on the middle of the magnet towards its end. 
    It is temporary because, after some time, the electrons divert from the alignment.
    Hence, it is a physical change.
  • Question 6
    1 / -0
    The cells used in a wrist watch undergo:
    Solution

    Physical changes are reversible and, no new substance is formed. An example is the melting of ice. Periodic changes are the ones that occur after regular intervals of time. An example of periodic change is the beating of the heart. Chemical changes are irreversible. New substances are formed during a chemical change.  
    The Cells used in wristwatches are called button cells. These cells undergo chemical reactions to produce energy that is used in the functioning of the watch. Thus, option C is correct.
  • Question 7
    1 / -0

    Which of the following is a feature of physical change?

    Solution

    A physical change is any change in matter that involves the substance going from one physical state to another. 

    It does not lose its original properties because no new formation takes place when changing from one phase to another. 

    A substance can go from a solid to a liquid, a liquid to a gas, a gas to a liquid, a liquid to a solid, a solid to a gas, or a gas to a solid.

    Hence, option D is correct.

  • Question 8
    1 / -0
    Rusting of iron is a chemical change because:
    Solution
    A change in which one or more new substances are formed is known as chemical change.
    When the iron is exposed to air and moisture, rust formation takes place. Rust is nothing but iron oxide; a new substance formed out of the reaction. The colour of the surface of the iron also changes. Hence, rusting of iron is a chemical change.
  • Question 9
    1 / -0

    Pick out the chemical change from the following.

    Solution
    The burning of coal in the air is a chemical change:
    $$C+O_2\rightarrow CO_2$$
    If there is insufficient oxygen then carbon monoxide is formed:
    $$ 2C + O_2\rightarrow 2CO$$
    Coal combustion releases nitrogen oxides, sulfur dioxide, particulate matter, mercury, and dozens of other substances known to be hazardous to human health.
    Melting of ice and freezing of water are physical changes.
    Hence, option $$B$$ is correct.
  • Question 10
    1 / -0
    Bathroom fittings are plated with _________ to prevent rusting.
    Solution
    Bathroom fittings are plated with chromium to prevent rusting or corrosion. Metal objects made of iron and steel are usually electroplated with chromium.

    Hence, option $$D$$ is correct.
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