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)

Question

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.

Answer 1

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.