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Changes around Us Test - 5

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Changes around Us Test - 5
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Weekly Quiz Competition
  • Question 1
    1 / -0

    The making of a ring from gold is a __________ change and making a statue from wood is a __________ change.

    Solution
    The making of a ring from gold is a reversible change i.e once formed gold ornaments can be melted back to pure gold. 

    Making a statue from wood is an irreversible change, as once formed statue cannot be joined back to a big wood log.

    Hence, option B is correct.
  • Question 2
    1 / -0
    Identify the burning of wood change shown in image.

    Solution
    The burning of wood leads to the formation of new substances like ashes, carbon dioxide, water vapour, heat and light.
    $$Wood+{ O }_{ 2 }\longrightarrow Ashes+{ CO }_{ 2 }+{ H }_{ 2 }O$$
           (oxygen)                      (carbon    (water)
                                               dioxide)
    $$\therefore $$  This change is irreversible hence it is a chemical change.
  • Question 3
    1 / -0
    Which one of the following is a reversible change?
    Solution
    Wooden block or simply wood when cut into pieces cannot be restored.
    Flowers on blooming can never go back to being bud again.
    But melted ice can be frozen back to get ice, hence, melting of ice is a reversible change.
  • Question 4
    1 / -0
    Which of the following represents a reversible change?
    Solution
    A metal rod on heating expands (its length increases) and a metal rod on cooling contracts (its length decreases) both are examples of reversible changes. In reversible change, a substance might change how it feels or looks but it does not create a new material.
  • Question 5
    1 / -0
    Burnt sparklers and burnt books pages are examples of:
    Solution
    Irreversible changes $$-$$ because when they are burnt formation of gas and ashes takes place i.e. chemical reaction is taking place and new substances are formed which can't be reversed back.

    $$\text{Book pages} \quad \xrightarrow { \text{burning} } \quad { CO }_{ 2 }\ +\ \text{other substances.}$$ 

    Hence, the correct option is $$\text{B}.$$
  • Question 6
    1 / -0
     Iron adopts changes slowly and gradually by process of:
    Solution
    Iron adopts changes slowly and gradually by the process of rusting. 
    When an iron object is left in the damp air(or moisture), it gets covered with the red-brown flaky substance called rust and the process is known as rusting. 
    The process of depositing a layer of zinc on iron is known as galvanisation.
    The process of obtaining large crystals of pure substances from their solutions is known as crystallisation.
    Therefore the correct answer is rusting.
  • Question 7
    1 / -0
     Burnt crackers and burnt pages are examples of 
    Solution
    Burnt crackers and burnt pages are examples of irreversible changes, as they are permanent changes which cannot be undone. Once these materials are burnt in to ashes, the original materials cannot be recovered.
  • Question 8
    1 / -0
    The change of state of water from one form to another is:
    Solution
    The change of state in water is a physical change hence it is reversible. When water is heated it converts into vapors and when cooled till $$0^o C$$ it freezes to form ice. Water vapors on condensation converts into water.

    Hence, the option $$C$$ is correct.
  • Question 9
    1 / -0
     Heat gain makes ice to:
    Solution
    When heat flows through the ice, the ice will melt. The liquid has more energy than the solid, mainly because the molecular bonds in the solid adjust to low-energy positions. So energy, when flowed in, will convert the solid to the liquid.

    Freezing will happen if there is heat loss to ice.

    Evaporation will happen if the heat gain is very high that makes the ice convert to water vapor.

    The correct answer is option C.
  • Question 10
    1 / -0
    What is a reversible change?
    Solution

    A reversible change is a physical change that can be undone. A final substance can be converted back to the original substance without creating any new material.

    An irreversible change is a permanent change that cannot be undone.

    The correct answer is option $$C$$.
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