Chemical Reactions Lesson

Chemical reactions happen when:

• The atoms grow until a substance changes state.

• The products break apart into different substances

• The atoms rearrange themselves to form new reactants.

• The bonds between atoms in reactants break and reform to make new substances.

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What is a chemical equation?

• A shorthand notation that describes chemical reactions.

• A tool for scientists to solve for the reactants of a product.

• A tool for scientists to keep track of the changes they make to a substance.

• An equation that contains the same elements every time it is written.

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What happens during a chemical reaction where molecules break apart? They will:

• Dissolve into their original elements.

• Form new groups of atoms that make new substances.

• Completely dissolve into the environment.

• Make a copy with the atoms of another molecule.

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If there are 10 atoms in the reactants prior to chemical reaction, how many atoms will be in

the products?

• 5 atoms

• 10 atoms

• 500 atoms

• 1000 atoms

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The law of conservation of matter can be observed as the amount of matter before a reaction . . .

• Equals half the amount of matter after reaction.

• Is less than the amount of matter after reaction.

• is greater than the amount of matter after reaction.

• equals the amount of matter after reaction.

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What is one way to observe the law of conservation of matter?

• Measure the volume of the products and reactants.

• Measure the mass of the products and reactants.

• Measure the surface area of the products and reactants.

• Observe the products and reactants under a microscope.

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An exothermic reaction:

• always involves a solid and a liquid.

• causes a cooling effect in the surrounding environment.

• is a reaction in which the atoms in a substance expand or explode.

• releases more energy into the surroundings than it absorbs.

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Which of these is an example of an endothermic reaction that takes place without heat?

• a cold pack absorbing chemicals

• microwaving an egg

• a chicken kabob cooking on a grill

• All of the above.

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Which of these best describes electrolysis?

• The name for ALL chemical reactions.

• The division of nitrogen and carbon atoms.

• A reaction that occurs when an electric current passes through water.

• A reaction that occurs any time an electric current is introduced to a rock.

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Electrolysis of water (H₂O) produces which two substances?

• O₁₂ and H₁₂

• N₂ and H₂

• O₂₂ and N₁₁

• O₂ and H₂

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