what is always true according to the law of conservation of matter?

Question

the total number of molecules before and after a chemical rection stays the same.
atoms created during a chemical reaction must have the same mass as the atoms in the reactants.
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

Answer 1

According to the law of conservation of matter, the statement that is always true is:

Atoms can be rearranged during a chemical reaction but cannot be added or taken away.

This means that the total number of atoms remains constant throughout a chemical reaction, although they may be rearranged to form new molecules. The total mass of the reactants will equal the total mass of the products.

Answer 2

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 students claim is incorrect?

the reaction produced a gas that escaped the beaker.
the reaction did not change the physical properties of the liquids.
the product contained fewer atoms than the reactants.
the combined liquid was warmer than the two separate liquids.

Answer 3

The correct statement that explains why the student's claim is incorrect is:

The reaction produced a gas that escaped the beaker.

This indicates that during the combining of the two liquids, a gas was released into the air, which would account for the observed decrease in mass. According to the law of conservation of matter, matter is not lost; it may simply have changed phases or escaped from the closed system.