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Science

8th

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Chemical Reactions

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10 questions

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  • 1. Multiple Choice
    1 minute
    1 pt

    Chemical equations show the ratio of reactants and products involved in a chemical reaction. For example, 2 H2 + O2 → 2 H2O. How do balanced equations satisfy the Law of Conservation of Mass?

    The number of reactant molecules equals the number of product molecules.

    Every atom present in the reactants is also present in the products.

    The number of reactant molecules adds up to the number of product molecules

    The energy stored in bonds before and after the reaction is the same.

  • 2. Multiple Choice
    30 seconds
    1 pt

    Keesha performed a chemical reaction and the products looked quite different from the reactants. She knew the amount of matter had not changed due to the law of conservation of mass. According to the law of conservation of mass, what happens in a chemical reaction?

    Matter is not created or destroyed and the same amount of mass remains.

    A new kind of matter is created and the amount of mass either increases or decreases.

    Matter is not created or destroyed and the amount of mass may change after the reaction.

    New matter is created and changes form so that the mass of the reactants and the products will almost be equal.

  • 3. Multiple Choice
    30 seconds
    1 pt

    In a science lab, two students use a balance to measure the mass of a box containing a small crystal. The mass of the box is 12 grams (g). One of the students accidentally drops the box when removing it from the balance, and the crystal breaks into 20 pieces. What happens to the mass of the box and crystal after the crystal is broken?

    The mass remains the same.

    The mass cannot be determined.

    The mass increases by a factor of 20.

    The mass decreases by a factor of 20.

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