Suppose 10 atoms of carbon (C) react with 20 atoms of oxygen (O) to form 10 molecules of carbon dioxide (CO2
). According to the law of conservation of matter, how many atoms are present in this reaction?(1 point)
Responses
30
30
10
10
15
15
20
The correct answer is 30.
In the reaction, 10 atoms of carbon combine with 20 atoms of oxygen to form 10 molecules of carbon dioxide.
Each carbon dioxide molecule contains 1 carbon atom and 2 oxygen atoms.
Therefore, the total number of atoms present in the reaction is:
10 carbon atoms + (10 molecules × 2 oxygen atoms per molecule) = 10 + 20 = 30.
Which procedure could be used to demonstrate that matter is conserved during a chemical change or reaction?(1 point)
Responses
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.
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.
Find the mass of a stick of butter. Heat the butter until it melts. Find the mass of the melted butter.
Find the mass of a stick of butter. Heat the butter until it melts. Find the mass of the melted butter.
Find the mass of a log. Burn the log until it turns to ash and smoke. Find the mass of the ash.
Find the mass of a log. Burn the log until it turns to ash and smoke. Find the mass of the ash.
Find the mass of a piece of paper. Tear the paper into smaller pieces. Find the mass of the pieces.
Find the mass of a piece of paper. Tear the paper into smaller pieces. Find the mass of the pieces.
The correct answer is:
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.
This procedure involves measuring the mass of the reactants (acid and base) before the reaction and then measuring the mass of the products (water and salt) after the reaction. If matter is conserved, the mass of the reactants should be equal to the mass of the products.
What is always true according to the Law of Conservation of Matter?(1 point)
Responses
Atoms created during a chemical reaction must have the same mass as the atoms in the reactants.
Atoms created during a chemical reaction must have the same mass as the atoms in the reactants.
The total number of molecules before and after a chemical reaction stays the same.
The total number of molecules before and after a chemical reaction stays the same.
New molecules cannot be formed from the reactants during a chemical reaction.
New molecules cannot be formed from the reactants during a chemical reaction.
Atoms can be rearranged during a chemical reaction but cannot be added or taken away.
The correct answer is:
Atoms can be rearranged during a chemical reaction but cannot be added or taken away.
According to the Law of Conservation of Matter, the total number of atoms in a chemical reaction remains constant. Atoms can be rearranged to form new molecules, but no atoms are created or destroyed in the process.
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)
Responses
The combined liquid was warmer than the two separate liquids.
The combined liquid was warmer than the two separate liquids.
The reaction produced a gas that escaped the beaker.
The reaction produced a gas that escaped the beaker.
The reaction did not change the physical properties of the liquids.
The reaction did not change the physical properties of the liquids.
The product contained fewer atoms than the reactants.
The correct answer is:
The reaction produced a gas that escaped the beaker.
When a gas is produced during a chemical reaction, it can escape from the reaction vessel. This can result in a decrease in the total mass of the combined substances. However, the mass has not been lost - it has simply been converted into a different form (gas) that is no longer contained within the beaker. The Law of Conservation of Matter still holds true, as the total mass of the reactants and products, if accurately measured, would be the same.