Conservation of Mass

What is the main principle behind the law of conservation of matter?

• Mass does not change phase during a reaction.

• The total mass does not change during a reaction.

• Heat is added during a reaction for the mass to remain constant.

• Mass will always remain constant unless a change has occurred.

How many H atoms must be present in the second product that is formed?

• 1

• 2

• 3

• 4

Choose the statement that BEST compares the mass of the products to the mass of the reactants.

• The number of hydrogen atoms and oxygen atoms changes during the reaction, so the mass changes during the reaction.

• The number of hydrogen atoms and oxygen atoms changes during the reaction, but the mass does not change during the reaction.

• The number of hydrogen atoms and oxygen atoms is the same before and after the reaction, but the mass changes during the reaction.

• The number of hydrogen atoms and oxygen atoms is the same before and after the reaction, so the mass does not change during the reaction.

In a reaction, 12.99 grams of sodium reacts with 45.75 grams of chlorine. According to the law of conservation, how many grams of sodium chloride is formed?

• 29.37 grams

• 32.76 grams

• 58.74 grams

• 91.50 grams

A stack of newspapers is burned completely to ash in a laboratory. How does the resulting mass relate to the initial mass of the stack of newspapers?

• The mass of the gases and the ash should equal the mass of the initial stack of newspapers.

• The mass of the gases and the ash should be one-fourth the mass of the initial stack of newspapers.

• The mass of the gases and the ash should be one-half the mass of the initial stack of newspapers.

• The mass of the gases and the ash should be double the mass of the initial stack of newspapers.

Which chemical equation best supports the Law of Conservation of Mass?

• N₂ + 4H₂ → 2NH₃

• 2Na + 2Cl₂ → 3NaCl

• 4Al + 3O₂ → 2Al₂O₃

• 2KCl + 3O₂ → 2KClO₄

When a physical or chemical change occurs, the law of conservation of mass always applies. What happens to the atoms during a chemical change, according to this law?

• Atoms are created.

• Atoms are destroyed.

• Atoms are rearranged.

• Atoms are bonded.

What do the frozen water and the liquid water have in common?

• They have the same volume.

• They are the same shape.

• They have the same mass.

• They are in the same state.

CH₄ + _ O₂→ 2H₂O + CO₂

Which explains how this chemical equation would be balanced to support the Law of Conservation of Mass?

• place 1 before O₂

• place 2 before O₂
• place 3 before O₂

• place 4 before O₂

According to the Law of Conservation of Mass, how can the number of atoms after a reaction be explained?

• There will be 0 atoms since the product of the reaction is a compound.

• There will be 1 atom since the 2 molecules will combine into 1 compound.

• There will be 2 atoms since the 2 molecules will combine into 2 compounds.

• There will be 4 atoms since the number of atoms stays the same during a reaction.