This question tests understanding of the Law of Conservation of Matter: in chemical reactions, atoms are rearranged into new molecules but no atoms are created or destroyed. During a chemical reaction, the atoms present in the reactant molecules disconnect from their current bonding partners (bonds break) and reconnect with different atoms to form product molecules (new bonds form)—the key principle is that while the molecules change (H₂O reactants become H₂ and O₂ products), the atoms themselves are conserved: every atom in the products was present in the reactants, and every atom from the reactants appears in the products, meaning you can count atoms of each element and get the same number before and after the reaction. Counting atoms in the model before the reaction gives 6 total atoms: 4 hydrogen atoms (2 in each H₂O molecule) and 2 oxygen atoms (1 in each H₂O molecule), and counting after gives the same 6 total atoms: 4 hydrogen atoms (2 in each H₂ molecule) and 2 oxygen atoms (in the O₂ molecule)—the fact that these counts match, atom by atom, demonstrates the Law of Conservation of Matter. During the reaction, bonds broke: H-O bonds in water molecules, and new bonds formed: H-H bonds in hydrogen molecules and O=O bonds in oxygen molecules, but throughout this bond breaking and forming, every single atom remained (no atom vanished) and no new atoms appeared (no atoms created from nothing)—the atoms simply changed their bonding partners, which is what we mean by "rearranged." Choice A is correct because it accurately explains that H-O bonds break and H-H and O=O bonds form. Choice B incorrectly claims H-H and O=O bonds break, when actually these bonds are formed during the reaction (they exist in the products H₂ and O₂, not in the reactant H₂O). To verify atom conservation in chemical reactions: (1) count atoms of each element in all reactant molecules (count all H atoms, all O atoms, all C atoms, etc.), (2) count atoms of each element in all product molecules (same procedure), (3) compare the counts—they should match exactly (if 4 H in reactants, must be 4 H in products), (4) if counts match for every element, atoms are conserved; if they don't match, either you miscounted or the model is incorrect (unbalanced representation). The reason atoms are conserved is fundamental: atoms are the basic building blocks of matter and cannot be created, destroyed, or changed into different elements during chemical reactions (that requires nuclear reactions, not chemical reactions)—so in all chemical reactions, whether burning, rusting, cooking, or any other reaction, the atoms present at the start must all appear at the end, though they'll be bonded differently, in different molecules, creating substances with different properties.

This question tests understanding of the Law of Conservation of Matter: in chemical reactions, atoms are rearranged into new molecules but no atoms are created or destroyed. During a chemical reaction, the atoms present in the reactant molecules disconnect from their current bonding partners (bonds break) and reconnect with different atoms to form product molecules (new bonds form)—the key principle is that while the molecules change (N₂ and H₂ reactants become NH₃ products), the atoms themselves are conserved: every atom in the products was present in the reactants, and every atom from the reactants appears in the products, meaning you can count atoms of each element and get the same number before and after the reaction. Before the reaction, the reactants are 1 N₂ molecule (containing 2 nitrogen atoms) and 3 H₂ molecules (each containing 2 hydrogen atoms, giving 6 total hydrogen atoms: 3×2). After the reaction, the products are 2 NH₃ molecules, each containing 1 nitrogen atom and 3 hydrogen atoms, giving 2 total nitrogen atoms (2×1) and 6 total hydrogen atoms (2×3). Comparing the counts: 2 nitrogen before equals 2 nitrogen after, and 6 hydrogen before equals 6 hydrogen after—this demonstrates that atoms are conserved. The atoms rearranged (nitrogen atoms that were bonded N≡N are now bonded to H, hydrogen atoms that were bonded H-H are now bonded to N), but no nitrogen or hydrogen atoms were created or destroyed. Choice B is correct because it correctly states that there are 6 H atoms before and 6 H atoms after. Choice A incorrectly claims there are only 3 H atoms before the reaction, when actually counting the atoms shows 3 H₂ molecules × 2 H atoms per molecule = 6 H atoms total in the reactants. To verify atom conservation in chemical reactions: (1) count atoms of each element in all reactant molecules (count all H atoms, all O atoms, all C atoms, etc.), (2) count atoms of each element in all product molecules (same procedure), (3) compare the counts—they should match exactly (if 6 H in reactants, must be 6 H in products), (4) if counts match for every element, atoms are conserved; if they don't match, either you miscounted or the model is incorrect (unbalanced representation). The reason atoms are conserved is fundamental: atoms are the basic building blocks of matter and cannot be created, destroyed, or changed into different elements during chemical reactions (that requires nuclear reactions, not chemical reactions)—so in all chemical reactions, whether burning, rusting, cooking, or any other reaction, the atoms present at the start must all appear at the end, though they'll be bonded differently, in different molecules, creating substances with different properties.

This question tests understanding of the Law of Conservation of Matter: in chemical reactions, atoms are rearranged into new molecules but no atoms are created or destroyed. During a chemical reaction, the atoms present in the reactant molecules disconnect from their current bonding partners (bonds break) and reconnect with different atoms to form product molecules (new bonds form)—the key principle is that while the molecules change (H₂ and O₂ reactants become H₂O products), the atoms themselves are conserved: every atom in the products was present in the reactants, and every atom from the reactants appears in the products, meaning you can count atoms of each element and get the same number before and after the reaction. Before the reaction, the reactants are 2 H₂ molecules (4 H atoms) and 1 O₂ molecule (2 O atoms); after the reaction, the products are 2 H₂O molecules (4 H and 2 O)—comparing the counts: 4 H and 2 O before equals 4 H and 2 O after—this demonstrates that atoms are conserved; the atoms rearranged (H-H and O=O bonds to H-O bonds), but no atoms were created or destroyed. Choice B is correct because it correctly states that atoms are conserved with equal counts before and after (4 H and 2 O on both sides). Choice A incorrectly claims there are more oxygen atoms after because water has oxygen, when counting shows the same 2 O atoms before and after (no creation); Choice C makes a counting error, stating 2 H and 2 O before but 4 H and 1 O after, when actually it's 4 H and 2 O on both sides. To verify atom conservation in chemical reactions: (1) count atoms of each element in all reactant molecules (count all H atoms, all O atoms, etc.), (2) count atoms of each element in all product molecules (same procedure), (3) compare the counts—they should match exactly (if 4 H in reactants, must be 4 H in products), (4) if counts match for every element, atoms are conserved; if they don't match, either you miscounted or the model is incorrect (unbalanced representation). The reason atoms are conserved is fundamental: atoms are the basic building blocks of matter and cannot be created, destroyed, or changed into different elements during chemical reactions (that requires nuclear reactions, not chemical reactions)—so in all chemical reactions, whether burning, rusting, cooking, or any other reaction, the atoms present at the start must all appear at the end, though they'll be bonded differently, in different molecules, creating substances with different properties.

This question tests understanding of the Law of Conservation of Matter: in chemical reactions, atoms are rearranged into new molecules but no atoms are created or destroyed. During a chemical reaction, the atoms present in the reactant molecules disconnect from their current bonding partners (bonds break) and reconnect with different atoms to form product molecules (new bonds form)—the key principle is that while the molecules change (H₂ and O₂ reactants become H₂O products), the atoms themselves are conserved: every atom in the products was present in the reactants, and every atom from the reactants appears in the products, meaning you can count atoms of each element and get the same number before and after the reaction. For 2H₂ + O₂ → 2H₂O: Before the reaction, the reactants are [2 H₂ molecules (containing 4 total hydrogen atoms) and 1 O₂ molecule (containing 2 oxygen atoms)]. After the reaction, the products are [2 H₂O molecules, each containing 2 hydrogen and 1 oxygen, totaling 4 hydrogen and 2 oxygen atoms]. Comparing the counts: 4 hydrogen before equals 4 hydrogen after, and 2 oxygen before equals 2 oxygen after—this demonstrates that atoms are conserved. During the reaction, bonds broke: specific bonds like H–H and O=O in reactants and new bonds formed: specific bonds like H–O in products, but throughout this bond breaking and forming, every single atom remained (no atom vanished) and no new atoms appeared (no atoms created from nothing)—the atoms simply changed their bonding partners, which is what we mean by "rearranged." Choice C is correct because it accurately explains that atoms rearrange by changing bonding partners while staying present, specifically noting hydrogen atoms from H–H become bonded to oxygen in water but remain the same atoms. Choice A incorrectly claims atoms are destroyed when the H–H bonds break, when actually the Law of Conservation of Matter states atoms cannot be created or destroyed in chemical reactions—all atoms present after were present before, just rearranged. To verify atom conservation in chemical reactions: (1) count atoms of each element in all reactant molecules (count all H atoms, all O atoms, all C atoms, etc.), (2) count atoms of each element in all product molecules (same procedure), (3) compare the counts—they should match exactly (if 4 H in reactants, must be 4 H in products), (4) if counts match for every element, atoms are conserved; if they don't match, either you miscounted or the model is incorrect (unbalanced representation). The reason atoms are conserved is fundamental: atoms are the basic building blocks of matter and cannot be created, destroyed, or changed into different elements during chemical reactions (that requires nuclear reactions, not chemical reactions)—so in all chemical reactions, whether burning, rusting, cooking, or any other reaction, the atoms present at the start must all appear at the end, though they'll be bonded differently, in different molecules, creating substances with different properties.

This question tests understanding of the Law of Conservation of Matter: in chemical reactions, atoms are rearranged into new molecules but no atoms are created or destroyed. During a chemical reaction, the atoms present in the reactant molecules disconnect from their current bonding partners (bonds break) and reconnect with different atoms to form product molecules (new bonds form)—the key principle is that while the molecules change (H₂O reactants become H₂ and O₂ products), the atoms themselves are conserved: every atom in the products was present in the reactants, and every atom from the reactants appears in the products, meaning you can count atoms of each element and get the same number before and after the reaction. Before the reaction, the reactants are 2 H₂O molecules (4 H and 2 O); after, 2 H₂ (4 H) and 1 O₂ (2 O)—comparing the counts: 4 H before equals 4 H after, and 2 O before equals 2 O after, demonstrating that atoms are conserved; the atoms rearranged (H-O-H bonds break, H-H and O=O bonds form), but no atoms were created or destroyed. Choice A is correct because it correctly states that atoms are conserved with equal counts of 4 H and 2 O before and after. Choice B incorrectly claims atoms are destroyed because there are fewer molecules after, when actually the Law of Conservation of Matter states atoms cannot be created or destroyed in chemical reactions—all atoms present after were present before, just rearranged, and molecule count can change without affecting atom conservation. To verify atom conservation in chemical reactions: (1) count atoms of each element in all reactant molecules, (2) count atoms of each element in all product molecules, (3) compare the counts—they should match exactly, (4) if counts match for every element, atoms are conserved; if they don't match, either you miscounted or the model is incorrect. The reason atoms are conserved is fundamental: atoms are the basic building blocks of matter and cannot be created, destroyed, or changed into different elements during chemical reactions (that requires nuclear reactions, not chemical reactions)—so in all chemical reactions, whether burning, rusting, cooking, or any other reaction, the atoms present at the start must all appear at the end, though they'll be bonded differently, in different molecules, creating substances with different properties.

This question tests understanding of the Law of Conservation of Matter: in chemical reactions, atoms are rearranged into new molecules but no atoms are created or destroyed. During a chemical reaction, the atoms present in the reactant molecules disconnect from their current bonding partners (bonds break) and reconnect with different atoms to form product molecules (new bonds form)—the key principle is that while the molecules change (CH₄ and O₂ reactants become CO₂ and H₂O products), the atoms themselves are conserved: every atom in the products was present in the reactants, and every atom from the reactants appears in the products, meaning you can count atoms of each element and get the same number before and after the reaction. Before the reaction, the reactants are 1 CH₄ molecule (containing 1 C and 4 H) and 2 O₂ molecules (each with 2 O, so 4 O total), giving 4 O atoms overall; after the reaction, the products are 1 CO₂ (1 C and 2 O) and 2 H₂O (each with 2 H and 1 O, so 4 H and 2 O), giving 4 O atoms total (2 from CO₂ + 2 from H₂O)—comparing the counts: 4 oxygen before equals 4 oxygen after—this demonstrates that atoms are conserved; during the reaction, bonds broke (C-H in CH₄, O=O in O₂) and new bonds formed (C=O in CO₂, H-O in H₂O), but throughout this bond breaking and forming, every single atom remained (no atom vanished) and no new atoms appeared (no atoms created from nothing)—the atoms simply changed their bonding partners, which is what we mean by 'rearranged.' Choice B is correct because it properly verifies conservation by counting atoms of oxygen, showing equal numbers (4 O) before and after. Choice A makes a counting error, stating 2 O before but 4 O after, when carefully counting the atoms in the model shows 4 O before (2 O₂ molecules × 2 O each) and 4 O after (2 in CO₂ + 1 each in 2 H₂O); Choice C incorrectly claims 4 O before but 3 O after, which is a miscount since products have 4 O total. To verify atom conservation in chemical reactions: (1) count atoms of each element in all reactant molecules (count all H atoms, all O atoms, all C atoms, etc.), (2) count atoms of each element in all product molecules (same procedure), (3) compare the counts—they should match exactly (if 4 O in reactants, must be 4 O in products), (4) if counts match for every element, atoms are conserved; if they don't match, either you miscounted or the model is incorrect (unbalanced representation). The reason atoms are conserved is fundamental: atoms are the basic building blocks of matter and cannot be created, destroyed, or changed into different elements during chemical reactions (that requires nuclear reactions, not chemical reactions)—so in all chemical reactions, whether burning, rusting, cooking, or any other reaction, the atoms present at the start must all appear at the end, though they'll be bonded differently, in different molecules, creating substances with different properties.

This question tests understanding of the Law of Conservation of Matter: in chemical reactions, atoms are rearranged into new molecules but no atoms are created or destroyed. During a chemical reaction, the atoms present in the reactant molecules disconnect from their current bonding partners (bonds break) and reconnect with different atoms to form product molecules (new bonds form)—the key principle is that while the molecules change (CH₄ and O₂ reactants become CO₂ and H₂O products), the atoms themselves are conserved: every atom in the products was present in the reactants, and every atom from the reactants appears in the products, meaning you can count atoms of each element and get the same number before and after the reaction. Before the reaction, the reactants are 1 CH₄ molecule (containing 1 C and 4 H) and 2 O₂ molecules (containing 4 total O atoms); after the reaction, the products are 1 CO₂ molecule (1 C and 2 O) and 2 H₂O molecules (4 H and 2 O), giving total 1 C, 4 H, 4 O before and after—comparing the counts for oxygen specifically: 4 O before equals 4 O after, demonstrating that oxygen atoms are conserved; the atoms rearranged (C-H bonds and O=O bonds break, C=O and H-O bonds form), but no atoms were created or destroyed. Choice B is correct because it accurately states there are 4 O atoms before and 4 O atoms after, properly verifying conservation by counting oxygen atoms. Choice A makes a counting error, stating 2 O atoms before but 4 O after, when carefully counting the atoms in the model shows 4 O before (2 O₂ means 4 O) and 4 O after (2 in CO₂ + 2 in 2 H₂O). To verify atom conservation in chemical reactions: (1) count atoms of each element in all reactant molecules, (2) count atoms of each element in all product molecules, (3) compare the counts—they should match exactly, (4) if counts match for every element, atoms are conserved; if they don't match, either you miscounted or the model is incorrect. The reason atoms are conserved is fundamental: atoms are the basic building blocks of matter and cannot be created, destroyed, or changed into different elements during chemical reactions (that requires nuclear reactions, not chemical reactions)—so in all chemical reactions, whether burning, rusting, cooking, or any other reaction, the atoms present at the start must all appear at the end, though they'll be bonded differently, in different molecules, creating substances with different properties.

This question tests understanding of the Law of Conservation of Matter: in chemical reactions, atoms are rearranged into new molecules but no atoms are created or destroyed. During a chemical reaction, the atoms present in the reactant molecules disconnect from their current bonding partners (bonds break) and reconnect with different atoms to form product molecules (new bonds form)—the key principle is that while the molecules change (N₂ and H₂ reactants become NH₃ products), the atoms themselves are conserved: every atom in the products was present in the reactants, and every atom from the reactants appears in the products, meaning you can count atoms of each element and get the same number before and after the reaction. Before the reaction, the reactants are 1 N₂ molecule (containing 2 nitrogen atoms) and 3 H₂ molecules (containing 6 total hydrogen atoms: 2 in each molecule). After the reaction, the products are 2 NH₃ molecules, each containing 1 nitrogen atom and 3 hydrogen atoms, giving 2 total nitrogen atoms (2×1) and 6 total hydrogen atoms (2×3). Comparing the counts: 2 nitrogen before equals 2 nitrogen after, and 6 hydrogen before equals 6 hydrogen after—this demonstrates that atoms are conserved. The atoms rearranged (nitrogen atoms that were bonded N≡N are now bonded to H, hydrogen atoms that were bonded H-H are now bonded to N), but no nitrogen or hydrogen atoms were created or destroyed. Choice B is correct because it correctly states that matter is conserved with 2 N atoms and 6 H atoms before and after. Choice A incorrectly claims matter is not conserved because there are 4 molecules after but only 4 molecules before, when actually counting shows 4 molecules before (1 N₂ + 3 H₂) and 2 molecules after (2 NH₃)—but molecule count doesn't determine conservation, atom count does. To verify atom conservation in chemical reactions: (1) count atoms of each element in all reactant molecules (count all H atoms, all O atoms, all C atoms, etc.), (2) count atoms of each element in all product molecules (same procedure), (3) compare the counts—they should match exactly (if 6 H in reactants, must be 6 H in products), (4) if counts match for every element, atoms are conserved; if they don't match, either you miscounted or the model is incorrect (unbalanced representation). The reason atoms are conserved is fundamental: atoms are the basic building blocks of matter and cannot be created, destroyed, or changed into different elements during chemical reactions (that requires nuclear reactions, not chemical reactions)—so in all chemical reactions, whether burning, rusting, cooking, or any other reaction, the atoms present at the start must all appear at the end, though they'll be bonded differently, in different molecules, creating substances with different properties.

This question tests understanding of the Law of Conservation of Matter: in chemical reactions, atoms are rearranged into new molecules but no atoms are created or destroyed. During a chemical reaction, the atoms present in the reactant molecules disconnect from their current bonding partners (bonds break) and reconnect with different atoms to form product molecules (new bonds form)—the key principle is that while the molecules change (CH₄ and O₂ reactants become CO₂ and H₂O products), the atoms themselves are conserved: every atom in the products was present in the reactants, and every atom from the reactants appears in the products, meaning you can count atoms of each element and get the same number before and after the reaction. For CH₄ + 2O₂ → CO₂ + 2H₂O: Before the reaction, the reactants are [1 CH₄ molecule (containing 1 carbon and 4 hydrogen atoms) and 2 O₂ molecules (each containing 2 oxygen atoms, totaling 4 oxygen atoms)]. After the reaction, the products are [1 CO₂ molecule (containing 1 carbon and 2 oxygen atoms) and 2 H₂O molecules (each containing 2 hydrogen and 1 oxygen, totaling 4 hydrogen and 2 oxygen), giving overall 1 carbon, 4 hydrogen, and 4 oxygen atoms]. Comparing the counts: 1 carbon before equals 1 carbon after, 4 hydrogen before equals 4 hydrogen after, and 4 oxygen before equals 4 oxygen after—this demonstrates that atoms are conserved. The atoms rearranged (carbon atoms that were bonded to H are now bonded to O, oxygen atoms from O=O are now in CO₂ and H₂O), but no atoms were created or destroyed. Choice B is correct because it properly verifies conservation by counting atoms of oxygen correctly as 4 before and 4 after. Choice A incorrectly claims before: 2 O atoms; after: 4 O atoms, when carefully counting shows 4 O before (2 O₂ means 4 O atoms) and 4 O after (2 in CO₂ + 2 in 2H₂O). To verify atom conservation in chemical reactions: (1) count atoms of each element in all reactant molecules (count all H atoms, all O atoms, all C atoms, etc.), (2) count atoms of each element in all product molecules (same procedure), (3) compare the counts—they should match exactly (if 4 H in reactants, must be 4 H in products), (4) if counts match for every element, atoms are conserved; if they don't match, either you miscounted or the model is incorrect (unbalanced representation). The reason atoms are conserved is fundamental: atoms are the basic building blocks of matter and cannot be created, destroyed, or changed into different elements during chemical reactions (that requires nuclear reactions, not chemical reactions)—so in all chemical reactions, whether burning, rusting, cooking, or any other reaction, the atoms present at the start must all appear at the end, though they'll be bonded differently, in different molecules, creating substances with different properties.

This question tests understanding of the Law of Conservation of Matter: in chemical reactions, atoms are rearranged into new molecules but no atoms are created or destroyed. During a chemical reaction, the atoms present in the reactant molecules disconnect from their current bonding partners (bonds break) and reconnect with different atoms to form product molecules (new bonds form)—the key principle is that while the molecules change (H₂ and O₂ reactants become H₂O products), the atoms themselves are conserved: every atom in the products was present in the reactants, and every atom from the reactants appears in the products, meaning you can count atoms of each element and get the same number before and after the reaction. Counting atoms in the model before the reaction gives 6 total atoms: 4 hydrogen atoms (2 in each H₂ molecule) and 2 oxygen atoms (in the O₂ molecule), and counting after gives the same 6 total atoms: 4 hydrogen atoms (2 in each H₂O molecule) and 2 oxygen atoms (1 in each H₂O molecule)—the fact that these counts match, atom by atom, demonstrates the Law of Conservation of Matter. During the reaction, bonds broke: H-H bonds in hydrogen molecules and O=O bonds in oxygen molecules, and new bonds formed: H-O bonds in water molecules, but throughout this bond breaking and forming, every single atom remained (no atom vanished) and no new atoms appeared (no atoms created from nothing)—the atoms simply changed their bonding partners, which is what we mean by "rearranged." Choice B is correct because it accurately explains that the same atoms are present but H-H and O=O bonds break and new H-O bonds form. Choice A incorrectly claims hydrogen atoms become oxygen atoms, when actually atoms stay the same element—hydrogen atoms remain hydrogen atoms and oxygen atoms remain oxygen atoms, they just change which atoms they're bonded to. To verify atom conservation in chemical reactions: (1) count atoms of each element in all reactant molecules (count all H atoms, all O atoms, all C atoms, etc.), (2) count atoms of each element in all product molecules (same procedure), (3) compare the counts—they should match exactly (if 4 H in reactants, must be 4 H in products), (4) if counts match for every element, atoms are conserved; if they don't match, either you miscounted or the model is incorrect (unbalanced representation). The reason atoms are conserved is fundamental: atoms are the basic building blocks of matter and cannot be created, destroyed, or changed into different elements during chemical reactions (that requires nuclear reactions, not chemical reactions)—so in all chemical reactions, whether burning, rusting, cooking, or any other reaction, the atoms present at the start must all appear at the end, though they'll be bonded differently, in different molecules, creating substances with different properties.