Question

conservation of mass in chemical reactions: investigating the rearrangement of atoms (including photosynthesis)
when a chemical reaction happens, the substances you start with (called reactants) change into new substances (called products). however, the total mass before and after the reaction stays the same. this is called the law of conservation of mass. the atoms in the reactants are not destroyed or created—they are simply rearranged to make new products.
an important example of a chemical reaction in nature is photosynthesis. plants use water (h_2o), carbon dioxide (co_2), and sunlight to make glucose (c_6h_{12}o_6) and oxygen (o_2). the chemical equation for photosynthesis is:
6 co_2 + 6 h_2o + light energy \
ightarrow c_6h_{12}o_6 + 6 o_2
notice how the number and type of atoms on each side of the equation are the same. this shows that mass is conserved—the atoms are just rearranged.
fill in the blank: fill in the blank with the correct words.

1. the law of __________ of mass says that mass is not created or destroyed in a chemical reaction.
2. in a chemical reaction, atoms are __________ to make new substances.
3. the substances you start with in a chemical reaction are called __________.
4. in photosynthesis, plants use sunlight to turn carbon dioxide and water into glucose and __________.
5. the number and type of __________ stays the same before and after a chemical reaction.

word bank: products, conservation, rearranged, oxygen, atoms, reactants
multiple choice questions: choose the correct answer from the choices for each question.

1. which statement best describes what happens to atoms during a chemical reaction?

a) atoms disappear and new ones are created
b) atoms are rearranged into new combinations
c) atoms change into energy
d) atoms shrink

1. what does the law of conservation of mass state?

a) mass can be created
b) mass can be destroyed
c) mass is always the same before and after a chemical reaction
d) mass only changes if there is heat

1. in the photosynthesis equation, how many molecules of carbon dioxide are used?

a) 1
b) 6
c) 12
d) 0

1. after a chemical reaction, the mass of the products is:

a) greater than the mass of the reactants
b) less than the mass of the reactants

Explanation:

Fill in the Blank Answers:

1. The Law of Conservation of Mass says that mass is not created or destroyed in a chemical reaction. (From the text: "This is called the Law of Conservation of Mass.")
2. In a chemical reaction, atoms are rearranged to make new substances. (From the text: "the atoms in the reactants are not destroyed or created—they are simply rearranged to make new products")
3. The substances you start with in a chemical reaction are called reactants. (From the text: "the substances you start with (called reactants)")
4. In photosynthesis, plants use sunlight to turn carbon dioxide and water into glucose and oxygen. (From the photosynthesis equation: \( 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light energy}

ightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \))

1. The number and type of atoms stays the same before and after a chemical reaction. (From the text: "the number and type of atoms on each side of the equation are the same")

Multiple Choice Answers:

1. Which statement best describes what happens to atoms during a chemical reaction?

• B) Atoms are rearranged into new combinations (The text states: "the atoms in the reactants are not destroyed or created—they are simply rearranged to make new products.")

1. What does the Law of Conservation of Mass state?

• C) Mass is always the same before and after a chemical reaction (The text defines the law as: "the total mass before and after the reaction stays the same.")

1. In the photosynthesis equation, how many molecules of carbon dioxide are used?

• The equation is \( 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light energy}

ightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \), so B) 6 molecules of \( \text{CO}_2 \) are used.

1. After a chemical reaction, the mass of the products is:

• By the Law of Conservation of Mass, the total mass of products equals the total mass of reactants. However, the options provided (A: "Greater," B: "Less") are incomplete (likely a typo, as a third option like "Equal" is missing). If we assume the intended correct answer aligns with the law, the mass of products is equal to the mass of reactants—but based on the given options, if forced to choose between A/B, neither is strictly correct. However, if we infer a formatting error (e.g., a missing "C) Equal"), the correct principle is that mass is conserved.

Final Answers (Summarized):

1. Conservation
2. Rearranged
3. Reactants
4. Oxygen
5. Atoms
6. B) Atoms are rearranged into new combinations
7. C) Mass is always the same before and after a chemical reaction
8. B) 6
9. (Note: The provided options for Q9 are inconsistent with the Law of Conservation of Mass. The correct answer should be "Equal to the mass of reactants," but if only A/B are given, neither is correct. Assuming a typo, the intended answer likely relates to conservation, so the mass of products is equal to reactants.)

Answer:

Fill in the Blank Answers:

1. The Law of Conservation of Mass says that mass is not created or destroyed in a chemical reaction. (From the text: "This is called the Law of Conservation of Mass.")
2. In a chemical reaction, atoms are rearranged to make new substances. (From the text: "the atoms in the reactants are not destroyed or created—they are simply rearranged to make new products")
3. The substances you start with in a chemical reaction are called reactants. (From the text: "the substances you start with (called reactants)")
4. In photosynthesis, plants use sunlight to turn carbon dioxide and water into glucose and oxygen. (From the photosynthesis equation: \( 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light energy}

ightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \))

1. The number and type of atoms stays the same before and after a chemical reaction. (From the text: "the number and type of atoms on each side of the equation are the same")

Multiple Choice Answers:

1. Which statement best describes what happens to atoms during a chemical reaction?

• B) Atoms are rearranged into new combinations (The text states: "the atoms in the reactants are not destroyed or created—they are simply rearranged to make new products.")

1. What does the Law of Conservation of Mass state?

• C) Mass is always the same before and after a chemical reaction (The text defines the law as: "the total mass before and after the reaction stays the same.")

1. In the photosynthesis equation, how many molecules of carbon dioxide are used?

• The equation is \( 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light energy}

ightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \), so B) 6 molecules of \( \text{CO}_2 \) are used.

1. After a chemical reaction, the mass of the products is:

• By the Law of Conservation of Mass, the total mass of products equals the total mass of reactants. However, the options provided (A: "Greater," B: "Less") are incomplete (likely a typo, as a third option like "Equal" is missing). If we assume the intended correct answer aligns with the law, the mass of products is equal to the mass of reactants—but based on the given options, if forced to choose between A/B, neither is strictly correct. However, if we infer a formatting error (e.g., a missing "C) Equal"), the correct principle is that mass is conserved.

Final Answers (Summarized):

1. Conservation
2. Rearranged
3. Reactants
4. Oxygen
5. Atoms
6. B) Atoms are rearranged into new combinations
7. C) Mass is always the same before and after a chemical reaction
8. B) 6
9. (Note: The provided options for Q9 are inconsistent with the Law of Conservation of Mass. The correct answer should be "Equal to the mass of reactants," but if only A/B are given, neither is correct. Assuming a typo, the intended answer likely relates to conservation, so the mass of products is equal to reactants.)