1.Suppose 10 atoms of carbon (C) react with 20 atoms of oxygen (O). According to the Law of Conservation of Matter, how many atoms will there be in the product of this reaction?(1 point)
A. 20
B. 30***
C. 10
D. 15
2.Which procedure could be used to demonstrate that matter is conserved during a chemical change or reaction?(1 point)
A. Find the mass of a stick of butter. Heat the butter until it melts. Find the mass of the melted butter.
B. Find the mass of a piece of paper. Tear the paper into smaller pieces. Find the mass of the pieces.***
C. Find the mass of an acid and a base. Combine them to produce water and a salt. Find the mass of the water and salt.
D. Find the mass of a log. Burn the log until it turns to ash. Find the mass of the ash.
3.What is always true according to the Law of Conservation of Matter?(1 point)
A. The total number of molecules before and after a chemical reaction stays the same.
B. Atoms created during a chemical reaction must have the same mass as the atoms in the reactants.***
C. Atoms can be rearranged during a chemical reaction but cannot be added or taken away.
D. New molecules cannot be formed from the reactants during a chemical reaction.
4.A student combines two liquids in a beaker. She observes that the mass of the combined liquid is less than the mass of the two separate liquids. The student claims that this observation shows that matter is not conserved in chemical reactions. Which statement explains why the student’s claim is incorrect?(1 point)
A. The combined liquid was warmer than the two separate liquids.***
B. The product contained fewer atoms than the reactants.
C. The reaction produced a gas that escaped the beaker.
D. The reaction did not change the physical properties of the liquids.
1. According to the Law of Conservation of Matter, the total number of atoms before and after a chemical reaction remains constant. In this case, 10 atoms of carbon (C) react with 20 atoms of oxygen (O). The product of this reaction will have a total of 30 atoms. Therefore, the correct answer is B. 30.
2. To demonstrate that matter is conserved during a chemical change or reaction, one can use the procedure of finding the mass before and after the change. In this case, finding the mass of a piece of paper, tearing it into smaller pieces, and then finding the mass of the pieces would show that matter is conserved. Therefore, the correct answer is B. Find the mass of a piece of paper. Tear the paper into smaller pieces. Find the mass of the pieces.
3. According to the Law of Conservation of Matter, atoms can be rearranged during a chemical reaction but cannot be added or taken away. This means that the total mass of the reactants will always be equal to the total mass of the products. Therefore, the correct answer is C. Atoms can be rearranged during a chemical reaction but cannot be added or taken away.
4. The student's claim is incorrect because the observation that the mass of the combined liquid is less than the mass of the two separate liquids does not imply that matter is not conserved in chemical reactions. The most likely explanation for this observation is that the reaction produced a gas that escaped the beaker. When a gas is produced, it can escape and result in a decrease in the overall mass. Therefore, the correct answer is C. The reaction produced a gas that escaped the beaker.
1. To determine the number of atoms in the product of the reaction, we need to use stoichiometry. The balanced chemical equation for the reaction between carbon (C) and oxygen (O) is:
C + O2 --> CO2
From the equation, we can see that 1 atom of carbon reacts with 1 molecule of oxygen (O2) to produce 1 molecule of carbon dioxide (CO2). Since we have 10 atoms of carbon and 20 atoms of oxygen, we need to consider the limiting reactant. In this case, carbon is the limiting reactant because it is present in a smaller amount.
So, if 10 atoms of carbon react, we will form 10 molecules of CO2, and each CO2 molecule contains 1 carbon atom and 2 oxygen atoms. Therefore, the total number of atoms in the product will be:
10 molecules CO2 x (1 carbon atom + 2 oxygen atoms) = 10 carbon atoms + 20 oxygen atoms = 30 atoms
Therefore, the answer is B. 30 atoms.
2. To demonstrate that matter is conserved during a chemical change or reaction, we need to compare the mass of the reactants with the mass of the products. Based on this, the procedure that could be used is B. Find the mass of a piece of paper. Tear the paper into smaller pieces. Find the mass of the pieces.
By tearing the paper into smaller pieces, we are not creating or destroying any matter, only changing its physical form. Since the pieces still have the same mass as the original paper, this demonstrates the conservation of matter during the process.
3. According to the Law of Conservation of Matter, the statement that is always true is B. Atoms created during a chemical reaction must have the same mass as the atoms in the reactants.
The Law of Conservation of Matter states that matter cannot be created or destroyed in a chemical reaction. The total mass of the reactants must equal the total mass of the products. Therefore, the mass of the atoms in the reactants must be equal to the mass of the atoms in the products.
4. The correct statement that explains why the student's claim is incorrect is A. The combined liquid was warmer than the two separate liquids.
The decrease in mass observed by the student is likely due to evaporation. If the combined liquid was warmer than the separate liquids, some of the liquid may have evaporated, resulting in a decrease in mass. This is a physical change, not a chemical change, and does not violate the Law of Conservation of Matter.
A. 20
B. Find the mass of a stick of butter. Heat the butter until it melts. Find the mass of the melted butter.
B. Atoms created during a chemical reaction must have the same mass as the atoms in the reactants.
A. The combined liquid was warmer than the two separate liquids.